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Speaker 1: Get in touch with technology with tech Stuff from how

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Speaker 1: stuff works dot com. Hey there, and welcome to tech Stuff.

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Speaker 1: I'm your host Jonathan Strickland. I'm an executive producer with

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Speaker 1: how Stuff Works in I heart radio and I love

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Speaker 1: all things tech, and today we're going to take a

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Speaker 1: close look at how image sensors work in a classic

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Speaker 1: episode of tech Stuff. This episode originally published on February

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Speaker 1: twenty nine, two thousand twelve. It is called how Image

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Speaker 1: Sensors Work, and we're talking about the various sensors that

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Speaker 1: you would find in digital cameras. So I hope that

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Speaker 1: you enjoy this classic episode as Chris Palette and I

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Speaker 1: tackle this topic. So today we thought we would look

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Speaker 1: at something. Actually it was Chris's suggestion that we look

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Speaker 1: into this particular topic, which was the the topic of

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Speaker 1: image sensors and what they do and what the two

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Speaker 1: main types of image sensors, how they are different from

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Speaker 1: one another, and uh and I thought it was a

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Speaker 1: great idea. It's also a fairly complex topic. We do

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Speaker 1: have an article on how stuff works dot com that says,

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Speaker 1: what is the difference between c c D and CMO

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Speaker 1: s image sensors in a digital camera? And that's really

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Speaker 1: what we're gonna be talking about here. Um. So that

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Speaker 1: there is an article on the site, and that's a

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Speaker 1: nice short article if you want a quick overview, but

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Speaker 1: we're gonna go into some detail a little bit in

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Speaker 1: this podcast. And really the first thing you need to

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Speaker 1: know is that an image sensor is it's taking the

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Speaker 1: place of film, right, Yes, that's correct, Yeah, a long

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Speaker 1: and a long time ago in a galaxy that happens

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Speaker 1: to be right here where we're sitting. We did a

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Speaker 1: podcast on the megapixel myth um. I think a lot

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Speaker 1: of people equate uh, numbers with a way we have

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Speaker 1: with quality and they say, oh, well, I've got a

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Speaker 1: twelve megapixel camera that's obviously better than that six megapixel

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Speaker 1: camera I used to own. Well, it depends on what

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Speaker 1: you're doing with the photo. It also depends on again

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Speaker 1: the other qualities of that camera, right, and image sensors

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Speaker 1: have a lot more to do with the quality of

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Speaker 1: the photo. But in a way it really depends because

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Speaker 1: again this uh there, there's this this idea that there

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Speaker 1: are two different kinds, which kind is better? It depends

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Speaker 1: on what you're doing with that what are you taking

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Speaker 1: photos of? Um? And Uh, As it turns out they're

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Speaker 1: they're not really better than one another. Inherently, they're they're

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Speaker 1: better than one another for specific applications of the photographic technology,

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Speaker 1: and the quality of the two sensors is constantly getting

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Speaker 1: closer and closer, so that the things that one sensor

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Speaker 1: does better than the other start to become less distinct

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Speaker 1: over time because the technology is improving on both sides simultaneously. Uh. Now,

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Speaker 1: if we were to go back a little bit to

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Speaker 1: the early days of digital cameras, the distinction was was clear.

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Speaker 1: You know, you would say that, well, a professional photographer

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Speaker 1: would more likely have a cc D image sensor in

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Speaker 1: his or her camera. CCD meaning charge coupled device, charge

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Speaker 1: coupled device, that's that's one of the two types. And

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Speaker 1: someone who has say a relatively inexpensive of course, back

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Speaker 1: in the early day of digital cameras, that was definitely

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Speaker 1: relative eight billion dollars, only a thousand dollars, yes, princely

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Speaker 1: going back to that a thousand dollars as opposed to

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Speaker 1: say eight thousand dollars. But a person holding one of

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Speaker 1: those cameras might have a CMOS or a complementary metal

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Speaker 1: ox side semiconductor image sensor. Yes, they come up and say,

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Speaker 1: that's a wonderful shirt you're wearing today. That's that's such

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Speaker 1: a great picture you've taken. Have you lost weight? No,

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Speaker 1: it's not that kind of complimentary. I have a whole

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Speaker 1: joke about that, but I'm going to spare everybody because

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Speaker 1: we've already said the punch line. Anyway, these are the

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Speaker 1: two different sensors, and they do go about capturing data

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Speaker 1: a different way. Let's let's go into the basic way

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Speaker 1: a camera captures an image. I'm going to talk about

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Speaker 1: still camera here, so we're talking about cameras in general,

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Speaker 1: not necessarily film, more digital. Right, So, in general, what

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Speaker 1: happens is you've got a camera and you're pointing it

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Speaker 1: at something that you want to take a photo of.

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Speaker 1: Light is coming towards you. It's reflecting off of the

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Speaker 1: the subject of your photo. If light we're not reflecting

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Speaker 1: off the subject of your photo, it would either mean

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Speaker 1: you were in total darkness, in which case taking a

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Speaker 1: photo is not very helpful, or you're taking a picture

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Speaker 1: of a black hole because not even light can escape it.

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Speaker 1: That being said, they're actually looking at making a physical

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Speaker 1: picture of a black hole. Using radio telescopes, which is

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Speaker 1: so cool. That's the tangent. Anyway, so light is coming

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Speaker 1: from the subject a little bit is awesome. We should

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Speaker 1: do a full podcast us on that. But anyway, lights

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Speaker 1: coming from from the subject toward the camera and uh,

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Speaker 1: and the light passes through the lens. The purpose of

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Speaker 1: the lens is to focus that light toward a specific

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Speaker 1: point within the camera. It moves through the aperture, which

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Speaker 1: is the opening behind the lens that allows light to

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Speaker 1: pass through. There's a shutter that's there behind the aperture

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Speaker 1: which actually directs the light up towards the view finder.

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Speaker 1: For the old style cameras, you know, the ones that

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Speaker 1: don't have the you know, you're not looking at a

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Speaker 1: screen on the back, you're looking actually through a view finder. Well,

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Speaker 1: that light gets directed up by a mirror and that's

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Speaker 1: essentially attached to the shutter that makes the light go

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Speaker 1: up inside the camera. Then it hits a prism which

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Speaker 1: inverts the light. Because you may not know this, but

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Speaker 1: the light the image that's coming in. That's saying the

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Speaker 1: sensor is actually upside down from our perspective. Gasp. So

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Speaker 1: if you didn't have that prism there, the subject you're

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Speaker 1: looking at would be upside down. It would be like

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Speaker 1: everything you're making photos of was in Australia. That unless

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Speaker 1: you're Australian, in which case it's all in Detroit. So

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Speaker 1: that's the that's the way. If you're wondering why there's

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Speaker 1: all these giant car factories in Australia, it's not. It's

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Speaker 1: just because you didn't have that prism in there, right, Um, Okay,

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Speaker 1: that's a terrible joke, but no, the prism does invert

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Speaker 1: the light, so otherwise again upside down. So when you

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Speaker 1: press the button to capture an image, the shutter, the shutter,

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Speaker 1: the shutter release exactly, the shutter, the shutter moves out

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Speaker 1: of the way and instead of the light hitting that

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Speaker 1: mirror and going up to the prism and inverting, the

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Speaker 1: light hits either film in a film camera or an

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Speaker 1: image sensor in a digital camera. So really the shutter

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Speaker 1: just moves out of the way and then the light

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Speaker 1: hits the sensor and then you're good to go. It's

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Speaker 1: a little different with the digital cameras that are out

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Speaker 1: right now, but that's in general how the process works basics. Yeah, now,

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Speaker 1: and with cameras now, light maybe hitting the sensor constantly,

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Speaker 1: and the shutter itself is not a physical shutter. It's

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Speaker 1: just the way that the sensory captures data. And we'll

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Speaker 1: talk about that when we get to that point. There

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Speaker 1: are two different major types of shutters that we can

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Speaker 1: talk about. So that's the general process. Now, with film,

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Speaker 1: it's a chemical process. Light hits the film and then

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Speaker 1: some chemical reactions take place, and that's what allows you

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Speaker 1: to capture an image. Right. With image sensors, it's not chemical,

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Speaker 1: it's electrical. Right, you're converting light energy into an electronic signal. Yes,

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Speaker 1: and then you're gonna want to store to some medium. Yes, uh,

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Speaker 1: you know, typically some kind of flash memory device, depending

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Speaker 1: on on what kind of camera you have. You know,

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Speaker 1: there were some I think that that stored on CD,

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Speaker 1: so you know, your mileage may vary, but in general,

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Speaker 1: some sort of flash device on onto day's cameras. Yeah.

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Speaker 1: The old digital camcorders could record on on different kinds

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Speaker 1: of media and so, and digital camcorders are working under

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Speaker 1: the same general principles as digital still cameras, with some

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Speaker 1: you know, other differences, but we'll talk about that. Like

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Speaker 1: I said, so, now we get into the differences between

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Speaker 1: the two major types of sensors, the charge coupled device

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Speaker 1: and the complementary metal oxide semiconductor. So we're just gonna

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Speaker 1: go do cc D and CMOS from here on out,

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Speaker 1: I think, otherwise I'm just going to have tongue twisters

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Speaker 1: for the rest of the podcast. Yes, well, I just

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Speaker 1: wanted to make sure that people knew what it what

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Speaker 1: it stood for, obviously very important. So in in a

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Speaker 1: c c D sensor, every single pixel now, pixel, remember,

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Speaker 1: is a point of light. An image is made up

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Speaker 1: of pixels, millions of pixels. That's where the megapixel comes from. Right,

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Speaker 1: So a twelve megapixel camera is going to take twelve

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Speaker 1: mega pixels worth of pixels and within the dimensions of

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Speaker 1: that image, whereas an eight megapixel camera will use fewer

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Speaker 1: pixels for that same size. Right. But and that's where

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Speaker 1: our idea about resolution comes in. Sometimes you hear people

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Speaker 1: talk about a low resolution image, it may be that

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Speaker 1: it's got fewer pixels in that image so that you

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Speaker 1: can actually start seeing if if the pixels are large

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Speaker 1: enough and few enough, you can start seeing the borders

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Speaker 1: from one pixel to the next. It's not very smooth,

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Speaker 1: it's almost jagged. Well, yeah, I mean that this is

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Speaker 1: the benefit of having a high megapixel camera. If you

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Speaker 1: shoot it high quality, then you are capturing more more

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Speaker 1: pixels for a specific region of the image, and you

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Speaker 1: can you can render that photo in a larger format.

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Speaker 1: Um because when you shrink, when you when you compress

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Speaker 1: the size of photo and reduce it in size um,

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Speaker 1: the compute it or is able to you know, throw

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Speaker 1: out unnecessary information and that the image still is pretty

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Speaker 1: good looking. When you try to increase the size, the

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Speaker 1: computer has to sort of guess on you know, pixel

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Speaker 1: by pixel basis. Well, I mean, this color is sort

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Speaker 1: of a brown color. It looks like I could throw

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Speaker 1: something else in here similar. And that's why when you

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Speaker 1: increase the size of a photo, a digital photo, that

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Speaker 1: it starts to look kind of jaggedy and rough because

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Speaker 1: the computer is having to guess at what that information is.

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Speaker 1: So if you take a ten megapixel photo and shrink

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Speaker 1: it down, it's it's gonna look pretty good. But if

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Speaker 1: you try to take a two megapixel photo and blow

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Speaker 1: it up, it's not gonna be so pretty. Yeah, if

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Speaker 1: you think about it like a puzzle, Let's say that

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Speaker 1: you have a puzzle that has four pieces to it, well,

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Speaker 1: then you're gonna be able to see the division of

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Speaker 1: those those four pieces very clearly. If it has four

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Speaker 1: million pieces, then it's each of those pieces are individually

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Speaker 1: much tinier than those four giant ones. That's the air

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Speaker 1: issue is that the larger you blow something up, if

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Speaker 1: it's if it doesn't have enough mega pixels in it,

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Speaker 1: not megapixels, but enough pixels, then you're gonna start to notice.

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Speaker 1: But that being said, the general digital cameras that are

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Speaker 1: out there for the consumer market and the general way

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Speaker 1: the consumers use digital cameras, megapixels really don't matter because

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Speaker 1: most of us are not blowing images up to poster size.

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Speaker 1: Most of us are using them for online photo albums.

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Speaker 1: We might print a few out, but usually eight by

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Speaker 1: ten tends to be about the largest because most people

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Speaker 1: don't have printers capable of printing at a larger size,

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Speaker 1: and when you take it to somebody to have it printed,

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Speaker 1: it's kind of expensive, so a poster. Most of us

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Speaker 1: don't do that, so most of us don't need to

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Speaker 1: worry about megapixels at this point. Professional photographers, it's a

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Speaker 1: different story. So cc D sensor, each of those pixels

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Speaker 1: has a charge. The photons that are coming in and

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Speaker 1: hitting that image sensor are being transferred from from a

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Speaker 1: light energy from photons into electrons. Now UH, they have

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Speaker 1: UH there's an output node with a c c D

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Speaker 1: sensor where that is converted into voltage. It's buffered and

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Speaker 1: then sent to a different part of the camera so

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Speaker 1: that it will become an analog signal. So a CCD

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Speaker 1: sensor it's a very it's a very UH specific device

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Speaker 1: that doesn't it doesn't have a lot of other functionality

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Speaker 1: to it apart from the fact that it's taking in

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Speaker 1: light and converting it into voltage. UH. Now the pixel

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Speaker 1: is completely devoted to capturing light and it has a

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Speaker 1: very uniform output. So the that's that's sort of where

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Speaker 1: the the idea of CCD being high quality came from. UH.

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Speaker 1: It was very good at capturing the true essence of

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Speaker 1: whatever it is you're pointing your camera at. You don't

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Speaker 1: have to have a you don't have to worry about

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Speaker 1: low lighting effects that kind of stuff, or having uh

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Speaker 1: an image turn out too grainy if the light is

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Speaker 1: too low, which can happen with CMOS images, particularly from

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Speaker 1: a few years ago. It's a depending on where you

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Speaker 1: know where the manufacturer for your camera got the c

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Speaker 1: m O S sensor. Uh, you might not have as

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Speaker 1: big an issue taking low lighting uh images. But if

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Speaker 1: you've ever used a digital camera in a know, either

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Speaker 1: a dark or just a dem environment, and you look

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Speaker 1: at me like, this just doesn't look good. Now, when

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Speaker 1: I take a photo outside in the middle of the daytime,

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Speaker 1: it looks gorgeous, beautiful colors, very very distinct. Um. That's

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Speaker 1: part of the problem is that the CMOS sensor captures

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Speaker 1: it in a different way. In that case, every single

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Speaker 1: pixel has its own charge to voltage conversion. The c

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Speaker 1: c D, it's doing all of the pixels at once.

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Speaker 1: In CMOS, it's doing each pixel individually. And then the

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Speaker 1: sensor itself has other elements added to it that the

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Speaker 1: c c D sensor does not have. Remember we said

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Speaker 1: c c D kind of offloads the information once it's

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Speaker 1: been converted into electrical impulses to other chips, right, Well,

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Speaker 1: those elements are actually on a CMO S sensor. So

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Speaker 1: it's got amplifiers, it's got digitization circuits, so it's actually

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Speaker 1: converting the electricity into bits. On the sensor itself, it's

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Speaker 1: got noise reduction capabilities, and so that means that it

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Speaker 1: actually speeds up the process and it decreases the amount

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Speaker 1: of space you need within a camera because all of

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Speaker 1: those elements are found on a single chip as opposed

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Speaker 1: to having dedicated chips for these these specific functions. Unfortunately,

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Speaker 1: also reduces the amount of space it has for image

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Speaker 1: capture because all that stuff is on the same chip. Yes,

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Speaker 1: so that that you know, that's a downside, yes, so

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Speaker 1: you that was one of the arguments again early on,

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Speaker 1: was that c c D cameras could take sharper photos

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Speaker 1: than CMOS cameras, and that you know, it's almost there

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Speaker 1: was also an expense issue, right, c c D image

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Speaker 1: sensors tend to be more expensive than CMOS ones CMOS.

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Speaker 1: The process of manufacturer got so efficient that the price

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Speaker 1: started to come down, and that that's why those are

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Speaker 1: the sort of image sensors that you find in things

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Speaker 1: like smartphones. You know, smartphones that have cameras tend to

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Speaker 1: have CMOS sensors in them. They take up less space,

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Speaker 1: they put out less heat, they take less energy to

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Speaker 1: run um and they're very fast. So those are all

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Speaker 1: the qualities that people who are having a who wants

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Speaker 1: something in a nice slim form factor or if that's

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Speaker 1: what's important to them. So yeah, C C D S

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Speaker 1: image sensor might take a sharper quality photo in certain situations,

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Speaker 1: but it's also going to require a larger form factor,

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Speaker 1: and it does take more energy to run, and that

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Speaker 1: that energy is going to also mean more heat. Yes,

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Speaker 1: as we know, as electricity runs through a circuit, one

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Speaker 1: of the by products is heat. We haven't figured out

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Speaker 1: a way to get around that yet. It's just one

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Speaker 1: of those one of those realities that it's uh um. Basically,

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Speaker 1: it's inefficient enough where some of the energy is being

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Speaker 1: converted to heat energy instead of you know what it

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Speaker 1: is intended for. Right, Chris and I have a little

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Speaker 1: bit more to say about image sensors, but before we

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Speaker 1: get to that, let's take a quick break to thank

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Speaker 1: our sponsor. So, so now we've got down to the

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Speaker 1: the idea of these two different image sensors capturing uh

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Speaker 1: information in different ways um, and the fact that over

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Speaker 1: time both both types of sensors have developed to the

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Speaker 1: point where the differences between the two, apart from the

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Speaker 1: fundamental difference about how they collect information, have started to

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Speaker 1: to diminish. Right, So that you can find some professional

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Speaker 1: cameras out there now that you CMOS image sensors, whereas

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Speaker 1: you know, a few years ago that was really unheard of.

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Speaker 1: And you can also find some consumer cameras, especially in

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Speaker 1: the cam Quorter realm, that are using cc D image sensors,

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Speaker 1: which again for a while you just didn't hear about

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Speaker 1: because c c D cameras were so expensive. It was

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Speaker 1: pretty much reserved for professionals, you know, just consumers just

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Speaker 1: didn't necessarily have the money to drop on something like

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Speaker 1: that unless they were you know, one per centers. So yeah,

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Speaker 1: it's it's it's it's still a developing thing and we're

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Speaker 1: still seeing that kind of level out. But that and

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Speaker 1: the two technologies do still exist. They coexist, so it's

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Speaker 1: not like one has been abandoned on top of in

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Speaker 1: favor of the other, although that tends to there there's

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Speaker 1: usually someone predicting that every few years. Well sure, sure,

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Speaker 1: um yeah. A lot of the research that I did

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Speaker 1: for the podcast was from Teleedne Dolsa, which makes which

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Speaker 1: makes both types of sensors, and they had some really interesting,

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Speaker 1: uh comparative white papers and other information. If you're interested

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Speaker 1: in getting into the depths of it, it got some

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Speaker 1: of it got fairly complicated. UM. But basically they they

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Speaker 1: had one paper they said that they're, uh that image

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Speaker 1: sensors can be measured on basically eight different characteristics UM.

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Speaker 1: And these were responsivity, you know, basically how responsive that

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Speaker 1: the sensor is. Uh, it's dynamic range, uniformity, shuttering, UM, speed, windowing,

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Speaker 1: and anti blooming UM. And you know, again this is

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Speaker 1: kind of you know complex, but the the uh, it's

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Speaker 1: kind of funny because the way that the image sensor

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Speaker 1: captures information. UM. You know, depending on the type that

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Speaker 1: you're talking about, they're not really uh, it's really application specific.

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Speaker 1: UM some of them. Some of them really don't have

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Speaker 1: that much difference over the others. Like, for example, UM,

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Speaker 1: CMOS chips are known to be a little bit more responsive. UM.

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Speaker 1: But c c D s are have an advantage in

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Speaker 1: dynamic range. But basically they didn't say, you know, the

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Speaker 1: this one chip is better than the others. They said,

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Speaker 1: it has more to do with the manufacturing capability and

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Speaker 1: whether the chip has done right and is used in

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Speaker 1: their correct setting than it does UM, you know, for

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Speaker 1: a particular type of technology. Right, and you were mentioned

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Speaker 1: mentioning the fact that there are different shutters. In general,

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Speaker 1: a CMOS image sensor uses a rolling shutter. Uh, there's

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Speaker 1: nothing saying that it couldn't use the same sort of

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Speaker 1: shutter that SEC the image sensor does, which is a

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Speaker 1: global shutter. There's nothing saying that it couldn't. It's just

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Speaker 1: that all the camcorders I looked at specifically, because this

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Speaker 1: really plays more into video than than uh, still photography.

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Speaker 1: Although there's some crossover between the two. Um it said

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Speaker 1: that you could have a CMOS with a global shutter,

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Speaker 1: it's just that you don't find those. So what's the

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Speaker 1: between the global shutter and a rolling shutter? Well, a

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Speaker 1: rolling shutter to me. And when I the first I

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Speaker 1: read about this, the first thing I thought about was

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Speaker 1: a copier or a scanner where the image sensor you

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Speaker 1: put the document on the on the screen, you close

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Speaker 1: the UM the top of the lid, and you tell

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Speaker 1: it to go ahead and make a copy or make

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Speaker 1: a scan of it, and the image sensor travels down

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Speaker 1: the length of the document from the top to the

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Speaker 1: bottom or what exactly, and and it is going you

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Speaker 1: know from UM it's starting at a specific point and

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Speaker 1: capturing the entire document as it travels the length of

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Speaker 1: it and uh, you know, because it's going essentially line

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Speaker 1: by line. If you think about that in pixel terms,

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Speaker 1: is taking a row of pixels and then another row

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Speaker 1: of pixels and then a nighte you know, as it

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Speaker 1: goes down. Right, Yeah, I was thinking of it sort

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Speaker 1: of the way television works. Yes, where it'll it'll you

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Speaker 1: have a line by line from the top to the bottom.

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Speaker 1: Um will ignore the interpalation part, otherwise we have to

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Speaker 1: get really complicated. But anyway, the image is painted essentially

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Speaker 1: on your screen from the top to the bottom at

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Speaker 1: a rate that's so fast that your eye does not

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Speaker 1: detect that. It looks like it's all simultaneously projected to you,

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Speaker 1: but it's actually done line by line from the top

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Speaker 1: of the screen to the bottom of the screen. Same

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Speaker 1: thing with a rolling shutter. So when you take a

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Speaker 1: photo or you're using a camcorder, let's stick with cam quorters.

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Speaker 1: So if you're using a camcorder that has a rolling

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Speaker 1: shutter type of image sensor talking cmos, uh, the the

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Speaker 1: images being recorded from the top to the bottom over

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Speaker 1: and over and over again. Okay, so uh with a

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Speaker 1: c c D camera, it's a global shutter which means

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Speaker 1: that it's capturing all that data all at once, Yes,

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Speaker 1: sort of like film would. Yeah, so it's not it's

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Speaker 1: not um you know, it's not something that's gonna be scrolling.

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Speaker 1: It's all one image. So this means that the two

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Speaker 1: different types of image sensors are also prone to two

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Speaker 1: different kinds of flaws that can happen when you're using them. Well,

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Speaker 1: of course, I mean that's that's like any other types

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Speaker 1: of technology. Not everything is suited for every use, right,

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Speaker 1: So let's say that let's i'll talk about the different

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Speaker 1: flaws that you can find. C c D essentially has

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Speaker 1: one type of flaw that you can encounter, which is

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Speaker 1: called the smear effect. So smearing is let's say that

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Speaker 1: you've got a a you're taking an image of something

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Speaker 1: that has a bright light in it. Um Smearing is

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Speaker 1: this effect where you sort of see the light. You'll

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Speaker 1: see like a projection of light above and below it

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Speaker 1: or you know it's that's that's why it's called smear.

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Speaker 1: It's it's been extended beyond just a source of light itself.

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Speaker 1: It's kind of like a halo effect, though usually it's

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Speaker 1: more of at least in the samples. I've looked at.

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Speaker 1: It's more of a vertical thing where it looks like

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Speaker 1: it's almost like a ray of light that goes straight

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Speaker 1: up and down the the the screen from the source.

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Speaker 1: So that's one of the things that c c D

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Speaker 1: image sensors can fall victim to, but not CMOS. And

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Speaker 1: it's all because that global shutter exposes that image, the

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Speaker 1: whole image simultaneously, and it's all gathering that light, and

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Speaker 1: once the predetermined shutter speed for that global shutter has elapsed,

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Speaker 1: it stops gathering light, turns that that entire exposure into

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Speaker 1: an electronic image, and then starts again. And the rolling

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Speaker 1: shutter just doesn't have that same effects, so the smear

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Speaker 1: does not happen with that, and it's you know, it's

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Speaker 1: very noticeable. If you see the the effects of this,

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Speaker 1: you'd think, oh, well, that's unfortunate that there's this weird

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Speaker 1: shaft of light right there in the middle of the frame. Well,

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Speaker 1: that's that's it for the c c D. Okay, that's

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Speaker 1: the that's the one flaw that's c c D image

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Speaker 1: sensors can can fall victim to. But there's the one

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Speaker 1: known thing that people complain, the one thing that people

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Speaker 1: complain about. There are three three different ones for cmos.

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Speaker 1: The first is called skew. Okay, So you've got this

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Speaker 1: rolling shutter and it's going from top to bottom as

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Speaker 1: it's recording images. Now, this utter is going off u

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Speaker 1: multiple times per second. But let's say that you are

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Speaker 1: panning the camera very very quickly from one side to another,

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Speaker 1: so you're changing the view. Well, you're having a rolling

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Speaker 1: shutter and you're panning the camera. This can cause the

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Speaker 1: idea of skew. We have just a bit more information

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Speaker 1: to cover in this classic episode of tech stuff, but

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Speaker 1: before we get to that, let's take another quick break

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Speaker 1: to thank our sponsor. So let's say that you have

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Speaker 1: something that's uh, that's significant, a big thing that's in

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Speaker 1: the frame of the photo, maybe maybe like a tower.

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Speaker 1: All right, So you've got a tower in the frame

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Speaker 1: of your image, and you quickly pan from left to right. Well,

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Speaker 1: as you're panning, that shutter is rolling, and if your

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Speaker 1: pan is fast enough, then the shutter is actually going

429
00:25:55,680 --> 00:25:59,479
Speaker 1: to start building an image where the pixels at the

430
00:25:59,520 --> 00:26:03,040
Speaker 1: top of the image are further on one side than

431
00:26:03,080 --> 00:26:05,159
Speaker 1: the pixels that are at the bottom of that image.

432
00:26:06,359 --> 00:26:09,879
Speaker 1: Because it's not capturing all that data simultaneously. The outcome

433
00:26:10,040 --> 00:26:13,720
Speaker 1: of that is that you get a skewed image when

434
00:26:13,840 --> 00:26:17,080
Speaker 1: the output image itself is skewed. So that tower, which

435
00:26:17,160 --> 00:26:19,880
Speaker 1: might be perfectly straight when you look at it, when

436
00:26:19,880 --> 00:26:22,840
Speaker 1: you start looking back at the video and you're playing

437
00:26:22,840 --> 00:26:26,240
Speaker 1: it back really slowly, it suddenly looks like it's leaning

438
00:26:26,520 --> 00:26:29,240
Speaker 1: or it's diagonal. It's like that, you know, it's suddenly

439
00:26:29,280 --> 00:26:32,480
Speaker 1: not it's not true anymore. Now I understand what's wrong

440
00:26:32,520 --> 00:26:36,200
Speaker 1: with all those vacation pictures I took. Yeah, exactly, that's

441
00:26:36,240 --> 00:26:39,840
Speaker 1: the that's it. You know, it's no, it's not at all.

442
00:26:40,160 --> 00:26:44,080
Speaker 1: But anyway, that's that effect is because of that rolling shutter,

443
00:26:44,359 --> 00:26:46,240
Speaker 1: you know. And again a global shutter would not have

444
00:26:46,280 --> 00:26:48,639
Speaker 1: that problem because it's taking all that image, you know,

445
00:26:48,640 --> 00:26:51,560
Speaker 1: it's taking all the information all at once. The rolling

446
00:26:51,560 --> 00:26:54,040
Speaker 1: shutter is taking it bit by you know, line by line.

447
00:26:54,520 --> 00:26:57,399
Speaker 1: And again it's only if you're panning very quickly, because

448
00:26:57,560 --> 00:27:00,119
Speaker 1: it's this is going so many times per second that

449
00:27:00,440 --> 00:27:05,680
Speaker 1: if you're doing a nice slowe hand, it's it's not noticeable. Also,

450
00:27:05,760 --> 00:27:08,880
Speaker 1: you're more likely to prevent the kind of nausea that's

451
00:27:09,840 --> 00:27:13,560
Speaker 1: associated with the quick panning of Yeah, we'll get to

452
00:27:13,560 --> 00:27:19,840
Speaker 1: the human advantage to that too. Next is the wobble. Yes,

453
00:27:20,119 --> 00:27:24,960
Speaker 1: so you don't have this problem. No. This is wobble

454
00:27:25,119 --> 00:27:27,960
Speaker 1: is when you get sort of a weird, stretchy or

455
00:27:28,080 --> 00:27:31,000
Speaker 1: rubbery look to stuff that's going on in the video.

456
00:27:31,560 --> 00:27:35,080
Speaker 1: And it tends to happen with handheld footage, right because

457
00:27:35,119 --> 00:27:37,119
Speaker 1: you're when you're holding the camera, you don't have that

458
00:27:37,200 --> 00:27:40,160
Speaker 1: steady base that you would if you're using a tripod.

459
00:27:40,280 --> 00:27:44,439
Speaker 1: So let's say like a found footage film sure becoming

460
00:27:44,440 --> 00:27:47,480
Speaker 1: more and more popular these days, So something like all

461
00:27:47,520 --> 00:27:50,960
Speaker 1: onlines of Blair Witch or clover Field or or one

462
00:27:51,000 --> 00:27:56,080
Speaker 1: of those movies or or or vhs made by friends

463
00:27:56,119 --> 00:28:01,240
Speaker 1: of mine. Check it out. It's us. It just premiered

464
00:28:01,240 --> 00:28:05,040
Speaker 1: over at Sundance. Um, that's a shout out to my

465
00:28:05,040 --> 00:28:08,439
Speaker 1: buddies anyway, So same sort of thing. It's it's because

466
00:28:08,440 --> 00:28:11,080
Speaker 1: of that rolling shutter. The information is being captured line

467
00:28:11,119 --> 00:28:14,919
Speaker 1: by line. If your camera is not steady then and

468
00:28:14,960 --> 00:28:16,800
Speaker 1: if it's moving around quite a bit and at a

469
00:28:16,960 --> 00:28:21,520
Speaker 1: fairly fast pace, then it's the The images are not

470
00:28:21,560 --> 00:28:25,840
Speaker 1: going to be uh, they're not gonna be clear. They're

471
00:28:25,840 --> 00:28:29,240
Speaker 1: gonna end up having this wobbly, stretchy look. So let's

472
00:28:29,240 --> 00:28:32,560
Speaker 1: say you're panning uh down, so you've got you you

473
00:28:32,920 --> 00:28:34,919
Speaker 1: maybe you've got your looking at the top of that

474
00:28:34,960 --> 00:28:39,480
Speaker 1: tower and you start panning down very very quickly to say,

475
00:28:39,520 --> 00:28:44,479
Speaker 1: simulate a fall. So uh, we're panting down very very quickly.

476
00:28:44,800 --> 00:28:47,920
Speaker 1: That rolling shutter is going up from the top to

477
00:28:47,920 --> 00:28:52,400
Speaker 1: the bottom very quickly. As you are going down, the

478
00:28:52,480 --> 00:28:55,800
Speaker 1: shutter is going to uh. If you're matching the shutter

479
00:28:55,840 --> 00:28:58,360
Speaker 1: speed or getting close to the shutter speed, it's going

480
00:28:58,400 --> 00:29:02,480
Speaker 1: to make that building stretch out, it's gonna look very odd. Um.

481
00:29:02,600 --> 00:29:06,120
Speaker 1: And so that's another one of those issues. And again

482
00:29:06,240 --> 00:29:08,800
Speaker 1: the global shutter doesn't have that problem because it's not

483
00:29:09,360 --> 00:29:14,440
Speaker 1: it's not capturing information the same way. Uh. And then

484
00:29:14,680 --> 00:29:21,640
Speaker 1: finally there's partial exposure. Partial exposure happens when light is

485
00:29:21,760 --> 00:29:24,840
Speaker 1: hitting the shutter or the the image sensor at a

486
00:29:24,920 --> 00:29:27,840
Speaker 1: very particular moment and and the light is hitting it

487
00:29:28,040 --> 00:29:31,800
Speaker 1: just fast enough so that when the rolling shutter starts,

488
00:29:32,440 --> 00:29:35,720
Speaker 1: the light's not there. But before the rolling shutter has finished,

489
00:29:35,760 --> 00:29:39,880
Speaker 1: it's it's a journey across the image sensor. The light

490
00:29:39,920 --> 00:29:42,360
Speaker 1: has coming gone, which means that part of your image

491
00:29:42,440 --> 00:29:44,560
Speaker 1: is going to be much brighter than the rest of

492
00:29:44,560 --> 00:29:47,560
Speaker 1: your image. So if you think about your image as

493
00:29:48,120 --> 00:29:50,560
Speaker 1: h let's say you're taking a picture of, say a poster,

494
00:29:51,080 --> 00:29:53,680
Speaker 1: all right, you gotta you're looking at a poster and

495
00:29:53,840 --> 00:29:56,440
Speaker 1: there's a flash that goes off as you are taking

496
00:29:56,440 --> 00:29:59,080
Speaker 1: your image, and the flash is moving at a speed

497
00:29:59,160 --> 00:30:01,240
Speaker 1: is a very quick, flat moving it's moving on speed

498
00:30:01,280 --> 00:30:06,600
Speaker 1: that's faster than the rolling shutter is when you actually

499
00:30:06,600 --> 00:30:08,520
Speaker 1: look at that picture, when you're looking at the poster

500
00:30:08,680 --> 00:30:10,520
Speaker 1: in the back, it's gonna look like there's this one

501
00:30:10,640 --> 00:30:13,840
Speaker 1: band of the poster that's much more brightly lit than

502
00:30:13,880 --> 00:30:16,520
Speaker 1: the rest of the poster, and that's going to be

503
00:30:16,600 --> 00:30:19,960
Speaker 1: the moment when that flash hit the image sensor as

504
00:30:20,000 --> 00:30:24,600
Speaker 1: the rolling shutter was going down the sensor. So this

505
00:30:24,680 --> 00:30:27,160
Speaker 1: is another issue you have to work with your lighting

506
00:30:27,160 --> 00:30:31,200
Speaker 1: in order to avoid it. And uh you know it

507
00:30:31,240 --> 00:30:35,040
Speaker 1: can if you're using a flash that's a longer based flash,

508
00:30:35,200 --> 00:30:37,280
Speaker 1: you don't have to worry as much. This is why

509
00:30:37,880 --> 00:30:40,560
Speaker 1: partially why anyway part of it because it's most of

510
00:30:40,600 --> 00:30:44,480
Speaker 1: the the smartphone flashes or l e D s, But

511
00:30:44,720 --> 00:30:47,000
Speaker 1: it's also part of why if you ever take a

512
00:30:47,040 --> 00:30:50,720
Speaker 1: photo with a smartphone that uses an LED flash. It

513
00:30:50,960 --> 00:30:54,280
Speaker 1: tends to last a while. It's because if it didn't,

514
00:30:54,320 --> 00:30:56,080
Speaker 1: then your all your images would come out with this

515
00:30:56,200 --> 00:31:00,360
Speaker 1: weird banding issue. And you don't want bands in your

516
00:31:00,520 --> 00:31:04,480
Speaker 1: in your pictures unless you're at a concert. I'll be

517
00:31:04,520 --> 00:31:07,440
Speaker 1: taking some tonight. Awesome, I'm gonna go see. Day might

518
00:31:07,480 --> 00:31:11,200
Speaker 1: be giants and that's a shoutout. Today might be giants.

519
00:31:11,600 --> 00:31:15,719
Speaker 1: Everyone's getting shout outs today. It's free plug day on

520
00:31:15,800 --> 00:31:18,560
Speaker 1: tech stuff. Well, you know a lot of stuff on

521
00:31:18,560 --> 00:31:21,560
Speaker 1: tech stuff requires a plug. Yes, it's true. Not everything

522
00:31:21,640 --> 00:31:26,600
Speaker 1: is better reoperated. So, yeah, the c c D is

523
00:31:26,640 --> 00:31:30,560
Speaker 1: only prone to the smear issue, whereas CMOS has those

524
00:31:30,600 --> 00:31:34,160
Speaker 1: other three. If you have a decent camera, you shouldn't

525
00:31:34,200 --> 00:31:36,440
Speaker 1: have you know, in our are taking precautions. You just

526
00:31:36,680 --> 00:31:38,880
Speaker 1: have to worry about it, exactly. Yeah, if you if

527
00:31:38,920 --> 00:31:41,320
Speaker 1: you know what you're doing, you can get around these problems.

528
00:31:41,840 --> 00:31:43,880
Speaker 1: It's just that these are the ones that are the

529
00:31:43,960 --> 00:31:47,160
Speaker 1: cameras are prone to based upon the technology they use.

530
00:31:47,800 --> 00:31:50,200
Speaker 1: So it's not that every single image you're gonna take,

531
00:31:50,320 --> 00:31:54,520
Speaker 1: or even even like a significant percentage of the images

532
00:31:54,560 --> 00:31:58,400
Speaker 1: you'll take, will have problems associated with these issues that

533
00:31:58,400 --> 00:32:02,040
Speaker 1: I've talked about, but some of them might and the

534
00:32:02,120 --> 00:32:05,080
Speaker 1: reason why they they have those is because of the

535
00:32:05,080 --> 00:32:09,360
Speaker 1: technology itself. And again, you know, you just little basic

536
00:32:09,400 --> 00:32:12,160
Speaker 1: tricks that you can do, you know, just for example,

537
00:32:12,280 --> 00:32:16,080
Speaker 1: using a tripod whenever you can helps a lot, it'll

538
00:32:16,120 --> 00:32:18,200
Speaker 1: it'll really remove a lot of this. Also, you know,

539
00:32:18,320 --> 00:32:21,640
Speaker 1: most of most people aren't running around and jerking the

540
00:32:21,720 --> 00:32:24,880
Speaker 1: camera left and right so fast that these are really

541
00:32:25,040 --> 00:32:30,200
Speaker 1: coming into play. Uh And if you're using Instagram, really

542
00:32:30,200 --> 00:32:32,680
Speaker 1: you've made your image look so crappy already you don't

543
00:32:32,680 --> 00:32:37,960
Speaker 1: need to worry about these effects. That's that's just a

544
00:32:38,040 --> 00:32:45,800
Speaker 1: joke mostly. Alright, My wife uses Instagram a lot. What

545
00:32:45,960 --> 00:32:49,000
Speaker 1: a lovely old tiny photo of the Space Shuttle. I'm

546
00:32:49,040 --> 00:32:53,240
Speaker 1: so glad anyway, Uh so, yeah, I mean, so, which

547
00:32:53,760 --> 00:32:57,640
Speaker 1: which is better? Really kind of it really does depend

548
00:32:57,680 --> 00:33:01,320
Speaker 1: on what kind of photography you're going to be doing. Um,

549
00:33:01,360 --> 00:33:03,880
Speaker 1: you know, probably the biggest difference is whether you're doing

550
00:33:03,920 --> 00:33:07,680
Speaker 1: still photography or or video. And most of the time

551
00:33:07,680 --> 00:33:10,840
Speaker 1: when you're shopping for cameras, the type of sensor that's

552
00:33:10,840 --> 00:33:14,120
Speaker 1: and it is not necessarily the easiest information for you

553
00:33:14,160 --> 00:33:17,200
Speaker 1: to find out, although it does pay to to look

554
00:33:17,200 --> 00:33:19,480
Speaker 1: into that if you can and and actually do some

555
00:33:19,560 --> 00:33:22,640
Speaker 1: research on the sensor itself, because, like we said, the

556
00:33:22,640 --> 00:33:25,680
Speaker 1: sensor and the lens of the camera is going to

557
00:33:25,720 --> 00:33:27,800
Speaker 1: have a lot more to do with the quality of

558
00:33:27,840 --> 00:33:30,840
Speaker 1: the images that you get using that camera than how

559
00:33:30,840 --> 00:33:33,920
Speaker 1: many megapixels it has. So even if you go out

560
00:33:33,960 --> 00:33:35,959
Speaker 1: there and you buy a twelve megapixel camera and your

561
00:33:35,960 --> 00:33:39,240
Speaker 1: buddy has an eight megapixel camera, your buddy's images maybe

562
00:33:39,840 --> 00:33:43,239
Speaker 1: may look sharper and more vibrant than yours. Again, not

563
00:33:43,320 --> 00:33:45,560
Speaker 1: to do with the megapixels. It's more about the lens

564
00:33:45,600 --> 00:33:49,200
Speaker 1: and the sensory And of course, if you're you're planning

565
00:33:49,200 --> 00:33:51,680
Speaker 1: on dropping a lot of coin on a new camera,

566
00:33:52,520 --> 00:33:54,880
Speaker 1: probably would be a good idea if you read some

567
00:33:54,960 --> 00:33:59,080
Speaker 1: reviews from professionals to give you an idea of what

568
00:33:59,200 --> 00:34:01,880
Speaker 1: you expect to see. If if other people are using

569
00:34:01,920 --> 00:34:04,960
Speaker 1: it the same way, you will be um to get

570
00:34:05,000 --> 00:34:07,280
Speaker 1: to really get an idea of how you know whether

571
00:34:07,320 --> 00:34:09,439
Speaker 1: it's going to suit your needs, and that's the most

572
00:34:09,440 --> 00:34:13,800
Speaker 1: important thing. Very good, Yes, good advice from Mr Bled

573
00:34:14,280 --> 00:34:17,520
Speaker 1: And that wraps up another classic episode. Hope you guys

574
00:34:17,560 --> 00:34:20,120
Speaker 1: enjoyed it. If you have any suggestions for future episodes

575
00:34:20,120 --> 00:34:23,280
Speaker 1: of tech Stuff, why not, right in The email address

576
00:34:23,320 --> 00:34:25,600
Speaker 1: for the show is tech Stuff at how stuff works

577
00:34:25,640 --> 00:34:27,879
Speaker 1: dot com, or you can drop us a line by

578
00:34:27,920 --> 00:34:30,600
Speaker 1: going on over to tech Stuff podcast dot com and

579
00:34:30,640 --> 00:34:33,719
Speaker 1: following the links there to our various social media accounts.

580
00:34:33,960 --> 00:34:37,600
Speaker 1: You can also click on the little store icon in

581
00:34:37,680 --> 00:34:40,480
Speaker 1: the menu there and go on over there and purchase

582
00:34:40,520 --> 00:34:43,520
Speaker 1: stuff in the merchandise store. We have lots of fun designs,

583
00:34:43,560 --> 00:34:45,480
Speaker 1: and every purchase he make goes to help with the show,

584
00:34:45,560 --> 00:34:48,160
Speaker 1: so we greatly appreciate it, and I will talk to

585
00:34:48,160 --> 00:34:57,120
Speaker 1: you again really soon for more on this and thousands

586
00:34:57,120 --> 00:34:59,439
Speaker 1: of other topics. Because at how stuff works dot com,

587
00:35:02,719 --> 00:35:04,919
Speaker 1: wal won