WEBVTT - TechStuff Classic: How Image Sensors Work 0:00:04.120 --> 0:00:07.160 Get in touch with technology with tech Stuff from how 0:00:07.200 --> 0:00:13.720 stuff works dot com. Hey there, and welcome to tech Stuff. 0:00:13.760 --> 0:00:17.240 I'm your host Jonathan Strickland. I'm an executive producer with 0:00:17.320 --> 0:00:19.720 how Stuff Works in I heart radio and I love 0:00:19.840 --> 0:00:23.279 all things tech, and today we're going to take a 0:00:23.360 --> 0:00:27.600 close look at how image sensors work in a classic 0:00:27.760 --> 0:00:31.840 episode of tech Stuff. This episode originally published on February 0:00:31.880 --> 0:00:34.760 twenty nine, two thousand twelve. It is called how Image 0:00:34.840 --> 0:00:38.280 Sensors Work, and we're talking about the various sensors that 0:00:38.320 --> 0:00:41.040 you would find in digital cameras. So I hope that 0:00:41.120 --> 0:00:44.120 you enjoy this classic episode as Chris Palette and I 0:00:44.240 --> 0:00:47.520 tackle this topic. So today we thought we would look 0:00:47.560 --> 0:00:50.760 at something. Actually it was Chris's suggestion that we look 0:00:50.840 --> 0:00:55.680 into this particular topic, which was the the topic of 0:00:55.760 --> 0:00:59.360 image sensors and what they do and what the two 0:00:59.400 --> 0:01:02.319 main types of image sensors, how they are different from 0:01:02.360 --> 0:01:05.039 one another, and uh and I thought it was a 0:01:05.040 --> 0:01:08.440 great idea. It's also a fairly complex topic. We do 0:01:08.560 --> 0:01:11.480 have an article on how stuff works dot com that says, 0:01:11.560 --> 0:01:14.280 what is the difference between c c D and CMO 0:01:14.640 --> 0:01:17.520 s image sensors in a digital camera? And that's really 0:01:17.560 --> 0:01:20.000 what we're gonna be talking about here. Um. So that 0:01:20.200 --> 0:01:22.039 there is an article on the site, and that's a 0:01:22.120 --> 0:01:24.039 nice short article if you want a quick overview, but 0:01:24.040 --> 0:01:26.959 we're gonna go into some detail a little bit in 0:01:27.040 --> 0:01:30.200 this podcast. And really the first thing you need to 0:01:30.200 --> 0:01:33.440 know is that an image sensor is it's taking the 0:01:33.480 --> 0:01:37.399 place of film, right, Yes, that's correct, Yeah, a long 0:01:37.440 --> 0:01:39.360 and a long time ago in a galaxy that happens 0:01:39.360 --> 0:01:42.440 to be right here where we're sitting. We did a 0:01:42.480 --> 0:01:48.160 podcast on the megapixel myth um. I think a lot 0:01:48.200 --> 0:01:52.560 of people equate uh, numbers with a way we have 0:01:52.640 --> 0:01:54.480 with quality and they say, oh, well, I've got a 0:01:54.720 --> 0:01:58.120 twelve megapixel camera that's obviously better than that six megapixel 0:01:58.160 --> 0:02:01.120 camera I used to own. Well, it depends on what 0:02:01.160 --> 0:02:04.680 you're doing with the photo. It also depends on again 0:02:04.840 --> 0:02:08.600 the other qualities of that camera, right, and image sensors 0:02:08.639 --> 0:02:11.880 have a lot more to do with the quality of 0:02:11.919 --> 0:02:16.200 the photo. But in a way it really depends because 0:02:16.440 --> 0:02:20.280 again this uh there, there's this this idea that there 0:02:20.280 --> 0:02:23.520 are two different kinds, which kind is better? It depends 0:02:23.680 --> 0:02:26.720 on what you're doing with that what are you taking 0:02:26.720 --> 0:02:31.520 photos of? Um? And Uh, As it turns out they're 0:02:31.560 --> 0:02:35.600 they're not really better than one another. Inherently, they're they're 0:02:35.600 --> 0:02:40.840 better than one another for specific applications of the photographic technology, 0:02:40.960 --> 0:02:44.639 and the quality of the two sensors is constantly getting 0:02:44.680 --> 0:02:48.000 closer and closer, so that the things that one sensor 0:02:48.120 --> 0:02:51.280 does better than the other start to become less distinct 0:02:51.400 --> 0:02:57.840 over time because the technology is improving on both sides simultaneously. Uh. Now, 0:02:58.120 --> 0:02:59.800 if we were to go back a little bit to 0:02:59.840 --> 0:03:04.440 the early days of digital cameras, the distinction was was clear. 0:03:04.960 --> 0:03:07.680 You know, you would say that, well, a professional photographer 0:03:07.720 --> 0:03:11.600 would more likely have a cc D image sensor in 0:03:11.639 --> 0:03:16.080 his or her camera. CCD meaning charge coupled device, charge 0:03:16.080 --> 0:03:19.160 coupled device, that's that's one of the two types. And 0:03:19.480 --> 0:03:23.799 someone who has say a relatively inexpensive of course, back 0:03:23.800 --> 0:03:26.400 in the early day of digital cameras, that was definitely 0:03:26.400 --> 0:03:31.600 relative eight billion dollars, only a thousand dollars, yes, princely 0:03:32.240 --> 0:03:35.000 going back to that a thousand dollars as opposed to 0:03:35.080 --> 0:03:40.120 say eight thousand dollars. But a person holding one of 0:03:40.160 --> 0:03:44.240 those cameras might have a CMOS or a complementary metal 0:03:44.360 --> 0:03:49.040 ox side semiconductor image sensor. Yes, they come up and say, 0:03:49.080 --> 0:03:51.600 that's a wonderful shirt you're wearing today. That's that's such 0:03:51.640 --> 0:03:54.160 a great picture you've taken. Have you lost weight? No, 0:03:54.320 --> 0:03:56.440 it's not that kind of complimentary. I have a whole 0:03:56.520 --> 0:03:58.480 joke about that, but I'm going to spare everybody because 0:03:58.480 --> 0:04:01.320 we've already said the punch line. Anyway, these are the 0:04:01.360 --> 0:04:05.360 two different sensors, and they do go about capturing data 0:04:05.440 --> 0:04:09.119 a different way. Let's let's go into the basic way 0:04:09.160 --> 0:04:12.360 a camera captures an image. I'm going to talk about 0:04:12.400 --> 0:04:15.760 still camera here, so we're talking about cameras in general, 0:04:15.840 --> 0:04:19.599 not necessarily film, more digital. Right, So, in general, what 0:04:19.720 --> 0:04:22.039 happens is you've got a camera and you're pointing it 0:04:22.200 --> 0:04:24.040 at something that you want to take a photo of. 0:04:24.560 --> 0:04:28.520 Light is coming towards you. It's reflecting off of the 0:04:28.520 --> 0:04:33.440 the subject of your photo. If light we're not reflecting 0:04:33.480 --> 0:04:35.880 off the subject of your photo, it would either mean 0:04:35.920 --> 0:04:38.240 you were in total darkness, in which case taking a 0:04:38.279 --> 0:04:41.160 photo is not very helpful, or you're taking a picture 0:04:41.160 --> 0:04:44.360 of a black hole because not even light can escape it. 0:04:45.240 --> 0:04:48.040 That being said, they're actually looking at making a physical 0:04:48.160 --> 0:04:50.640 picture of a black hole. Using radio telescopes, which is 0:04:50.839 --> 0:04:54.960 so cool. That's the tangent. Anyway, so light is coming 0:04:55.080 --> 0:04:58.960 from the subject a little bit is awesome. We should 0:04:58.960 --> 0:05:01.679 do a full podcast us on that. But anyway, lights 0:05:01.720 --> 0:05:05.520 coming from from the subject toward the camera and uh, 0:05:05.560 --> 0:05:08.440 and the light passes through the lens. The purpose of 0:05:08.440 --> 0:05:11.479 the lens is to focus that light toward a specific 0:05:11.520 --> 0:05:14.680 point within the camera. It moves through the aperture, which 0:05:14.720 --> 0:05:17.080 is the opening behind the lens that allows light to 0:05:17.120 --> 0:05:22.560 pass through. There's a shutter that's there behind the aperture 0:05:23.160 --> 0:05:25.920 which actually directs the light up towards the view finder. 0:05:25.960 --> 0:05:28.159 For the old style cameras, you know, the ones that 0:05:28.240 --> 0:05:30.240 don't have the you know, you're not looking at a 0:05:30.279 --> 0:05:34.080 screen on the back, you're looking actually through a view finder. Well, 0:05:34.120 --> 0:05:37.560 that light gets directed up by a mirror and that's 0:05:37.760 --> 0:05:41.760 essentially attached to the shutter that makes the light go 0:05:42.000 --> 0:05:44.799 up inside the camera. Then it hits a prism which 0:05:44.920 --> 0:05:48.719 inverts the light. Because you may not know this, but 0:05:48.800 --> 0:05:50.719 the light the image that's coming in. That's saying the 0:05:50.760 --> 0:05:54.200 sensor is actually upside down from our perspective. Gasp. So 0:05:54.240 --> 0:05:56.599 if you didn't have that prism there, the subject you're 0:05:56.600 --> 0:05:58.960 looking at would be upside down. It would be like 0:05:59.000 --> 0:06:03.200 everything you're making photos of was in Australia. That unless 0:06:03.200 --> 0:06:06.599 you're Australian, in which case it's all in Detroit. So 0:06:07.160 --> 0:06:09.560 that's the that's the way. If you're wondering why there's 0:06:09.600 --> 0:06:13.320 all these giant car factories in Australia, it's not. It's 0:06:13.360 --> 0:06:16.719 just because you didn't have that prism in there, right, Um, Okay, 0:06:16.760 --> 0:06:19.799 that's a terrible joke, but no, the prism does invert 0:06:19.880 --> 0:06:25.000 the light, so otherwise again upside down. So when you 0:06:25.160 --> 0:06:30.080 press the button to capture an image, the shutter, the shutter, 0:06:30.440 --> 0:06:32.960 the shutter release exactly, the shutter, the shutter moves out 0:06:32.960 --> 0:06:35.520 of the way and instead of the light hitting that 0:06:35.600 --> 0:06:38.159 mirror and going up to the prism and inverting, the 0:06:38.279 --> 0:06:42.320 light hits either film in a film camera or an 0:06:42.360 --> 0:06:46.560 image sensor in a digital camera. So really the shutter 0:06:46.760 --> 0:06:48.880 just moves out of the way and then the light 0:06:48.960 --> 0:06:51.720 hits the sensor and then you're good to go. It's 0:06:51.760 --> 0:06:54.440 a little different with the digital cameras that are out 0:06:54.520 --> 0:06:59.760 right now, but that's in general how the process works basics. Yeah, now, 0:06:59.800 --> 0:07:04.240 and with cameras now, light maybe hitting the sensor constantly, 0:07:04.360 --> 0:07:08.240 and the shutter itself is not a physical shutter. It's 0:07:08.279 --> 0:07:12.640 just the way that the sensory captures data. And we'll 0:07:12.680 --> 0:07:15.800 talk about that when we get to that point. There 0:07:15.800 --> 0:07:17.880 are two different major types of shutters that we can 0:07:17.920 --> 0:07:22.200 talk about. So that's the general process. Now, with film, 0:07:22.240 --> 0:07:25.160 it's a chemical process. Light hits the film and then 0:07:25.200 --> 0:07:28.040 some chemical reactions take place, and that's what allows you 0:07:28.080 --> 0:07:32.640 to capture an image. Right. With image sensors, it's not chemical, 0:07:33.440 --> 0:07:38.559 it's electrical. Right, you're converting light energy into an electronic signal. Yes, 0:07:39.440 --> 0:07:44.080 and then you're gonna want to store to some medium. Yes, uh, 0:07:44.280 --> 0:07:48.520 you know, typically some kind of flash memory device, depending 0:07:48.520 --> 0:07:51.840 on on what kind of camera you have. You know, 0:07:51.960 --> 0:07:54.800 there were some I think that that stored on CD, 0:07:55.680 --> 0:07:58.400 so you know, your mileage may vary, but in general, 0:07:58.440 --> 0:08:00.840 some sort of flash device on onto day's cameras. Yeah. 0:08:00.880 --> 0:08:05.840 The old digital camcorders could record on on different kinds 0:08:05.880 --> 0:08:09.800 of media and so, and digital camcorders are working under 0:08:09.840 --> 0:08:14.760 the same general principles as digital still cameras, with some 0:08:15.040 --> 0:08:17.120 you know, other differences, but we'll talk about that. Like 0:08:17.160 --> 0:08:20.440 I said, so, now we get into the differences between 0:08:20.480 --> 0:08:23.800 the two major types of sensors, the charge coupled device 0:08:23.840 --> 0:08:27.600 and the complementary metal oxide semiconductor. So we're just gonna 0:08:27.600 --> 0:08:30.920 go do cc D and CMOS from here on out, 0:08:30.920 --> 0:08:34.080 I think, otherwise I'm just going to have tongue twisters 0:08:34.120 --> 0:08:35.760 for the rest of the podcast. Yes, well, I just 0:08:35.800 --> 0:08:37.360 wanted to make sure that people knew what it what 0:08:37.440 --> 0:08:40.960 it stood for, obviously very important. So in in a 0:08:41.040 --> 0:08:47.000 c c D sensor, every single pixel now, pixel, remember, 0:08:47.080 --> 0:08:49.760 is a point of light. An image is made up 0:08:49.880 --> 0:08:55.160 of pixels, millions of pixels. That's where the megapixel comes from. Right, 0:08:55.280 --> 0:08:59.400 So a twelve megapixel camera is going to take twelve 0:08:59.600 --> 0:09:03.520 mega pixels worth of pixels and within the dimensions of 0:09:03.559 --> 0:09:07.880 that image, whereas an eight megapixel camera will use fewer 0:09:07.920 --> 0:09:12.240 pixels for that same size. Right. But and that's where 0:09:12.360 --> 0:09:15.360 our idea about resolution comes in. Sometimes you hear people 0:09:15.400 --> 0:09:18.199 talk about a low resolution image, it may be that 0:09:18.320 --> 0:09:23.640 it's got fewer pixels in that image so that you 0:09:23.679 --> 0:09:26.400 can actually start seeing if if the pixels are large 0:09:26.480 --> 0:09:29.360 enough and few enough, you can start seeing the borders 0:09:29.840 --> 0:09:32.080 from one pixel to the next. It's not very smooth, 0:09:32.120 --> 0:09:34.760 it's almost jagged. Well, yeah, I mean that this is 0:09:34.800 --> 0:09:39.280 the benefit of having a high megapixel camera. If you 0:09:39.320 --> 0:09:43.200 shoot it high quality, then you are capturing more more 0:09:43.240 --> 0:09:46.600 pixels for a specific region of the image, and you 0:09:46.640 --> 0:09:51.800 can you can render that photo in a larger format. 0:09:52.440 --> 0:09:55.880 Um because when you shrink, when you when you compress 0:09:55.920 --> 0:09:59.400 the size of photo and reduce it in size um, 0:09:59.520 --> 0:10:01.840 the compute it or is able to you know, throw 0:10:01.840 --> 0:10:05.880 out unnecessary information and that the image still is pretty 0:10:05.880 --> 0:10:09.280 good looking. When you try to increase the size, the 0:10:09.280 --> 0:10:12.320 computer has to sort of guess on you know, pixel 0:10:12.360 --> 0:10:14.600 by pixel basis. Well, I mean, this color is sort 0:10:14.640 --> 0:10:17.240 of a brown color. It looks like I could throw 0:10:17.280 --> 0:10:19.400 something else in here similar. And that's why when you 0:10:19.440 --> 0:10:23.280 increase the size of a photo, a digital photo, that 0:10:23.360 --> 0:10:26.959 it starts to look kind of jaggedy and rough because 0:10:26.960 --> 0:10:29.440 the computer is having to guess at what that information is. 0:10:29.480 --> 0:10:32.680 So if you take a ten megapixel photo and shrink 0:10:32.720 --> 0:10:35.360 it down, it's it's gonna look pretty good. But if 0:10:35.360 --> 0:10:37.400 you try to take a two megapixel photo and blow 0:10:37.400 --> 0:10:40.080 it up, it's not gonna be so pretty. Yeah, if 0:10:40.080 --> 0:10:42.640 you think about it like a puzzle, Let's say that 0:10:42.679 --> 0:10:45.360 you have a puzzle that has four pieces to it, well, 0:10:45.400 --> 0:10:47.640 then you're gonna be able to see the division of 0:10:47.679 --> 0:10:51.400 those those four pieces very clearly. If it has four 0:10:51.520 --> 0:10:56.240 million pieces, then it's each of those pieces are individually 0:10:56.480 --> 0:11:00.120 much tinier than those four giant ones. That's the air 0:11:00.120 --> 0:11:03.040 issue is that the larger you blow something up, if 0:11:03.040 --> 0:11:05.440 it's if it doesn't have enough mega pixels in it, 0:11:05.480 --> 0:11:09.040 not megapixels, but enough pixels, then you're gonna start to notice. 0:11:09.120 --> 0:11:12.800 But that being said, the general digital cameras that are 0:11:12.800 --> 0:11:15.120 out there for the consumer market and the general way 0:11:15.160 --> 0:11:19.240 the consumers use digital cameras, megapixels really don't matter because 0:11:19.320 --> 0:11:22.320 most of us are not blowing images up to poster size. 0:11:22.640 --> 0:11:26.040 Most of us are using them for online photo albums. 0:11:26.040 --> 0:11:28.319 We might print a few out, but usually eight by 0:11:28.360 --> 0:11:31.000 ten tends to be about the largest because most people 0:11:31.040 --> 0:11:34.680 don't have printers capable of printing at a larger size, 0:11:34.960 --> 0:11:36.720 and when you take it to somebody to have it printed, 0:11:36.800 --> 0:11:39.840 it's kind of expensive, so a poster. Most of us 0:11:39.880 --> 0:11:41.800 don't do that, so most of us don't need to 0:11:41.800 --> 0:11:45.120 worry about megapixels at this point. Professional photographers, it's a 0:11:45.120 --> 0:11:49.599 different story. So cc D sensor, each of those pixels 0:11:50.240 --> 0:11:53.000 has a charge. The photons that are coming in and 0:11:53.040 --> 0:11:56.760 hitting that image sensor are being transferred from from a 0:11:57.280 --> 0:12:04.040 light energy from photons into electrons. Now UH, they have 0:12:04.320 --> 0:12:06.679 UH there's an output node with a c c D 0:12:06.880 --> 0:12:11.800 sensor where that is converted into voltage. It's buffered and 0:12:11.840 --> 0:12:17.079 then sent to a different part of the camera so 0:12:17.120 --> 0:12:21.040 that it will become an analog signal. So a CCD 0:12:21.120 --> 0:12:26.120 sensor it's a very it's a very UH specific device 0:12:26.200 --> 0:12:29.679 that doesn't it doesn't have a lot of other functionality 0:12:29.720 --> 0:12:31.880 to it apart from the fact that it's taking in 0:12:32.000 --> 0:12:37.200 light and converting it into voltage. UH. Now the pixel 0:12:37.320 --> 0:12:41.200 is completely devoted to capturing light and it has a 0:12:41.320 --> 0:12:45.480 very uniform output. So the that's that's sort of where 0:12:45.640 --> 0:12:50.040 the the idea of CCD being high quality came from. UH. 0:12:50.120 --> 0:12:55.520 It was very good at capturing the true essence of 0:12:55.559 --> 0:12:57.720 whatever it is you're pointing your camera at. You don't 0:12:57.760 --> 0:12:59.320 have to have a you don't have to worry about 0:12:59.360 --> 0:13:02.760 low lighting effects that kind of stuff, or having uh 0:13:02.800 --> 0:13:04.920 an image turn out too grainy if the light is 0:13:04.960 --> 0:13:10.680 too low, which can happen with CMOS images, particularly from 0:13:10.720 --> 0:13:15.319 a few years ago. It's a depending on where you 0:13:15.720 --> 0:13:18.360 know where the manufacturer for your camera got the c 0:13:18.559 --> 0:13:23.319 m O S sensor. Uh, you might not have as 0:13:23.360 --> 0:13:27.240 big an issue taking low lighting uh images. But if 0:13:27.280 --> 0:13:30.520 you've ever used a digital camera in a know, either 0:13:30.600 --> 0:13:33.079 a dark or just a dem environment, and you look 0:13:33.080 --> 0:13:35.120 at me like, this just doesn't look good. Now, when 0:13:35.160 --> 0:13:37.520 I take a photo outside in the middle of the daytime, 0:13:37.559 --> 0:13:43.520 it looks gorgeous, beautiful colors, very very distinct. Um. That's 0:13:43.760 --> 0:13:46.720 part of the problem is that the CMOS sensor captures 0:13:46.720 --> 0:13:49.760 it in a different way. In that case, every single 0:13:49.880 --> 0:13:54.480 pixel has its own charge to voltage conversion. The c 0:13:54.600 --> 0:13:56.640 c D, it's doing all of the pixels at once. 0:13:56.960 --> 0:14:01.839 In CMOS, it's doing each pixel individually. And then the 0:14:01.880 --> 0:14:06.240 sensor itself has other elements added to it that the 0:14:06.320 --> 0:14:08.840 c c D sensor does not have. Remember we said 0:14:08.880 --> 0:14:12.520 c c D kind of offloads the information once it's 0:14:12.520 --> 0:14:17.960 been converted into electrical impulses to other chips, right, Well, 0:14:17.960 --> 0:14:21.760 those elements are actually on a CMO S sensor. So 0:14:21.800 --> 0:14:26.120 it's got amplifiers, it's got digitization circuits, so it's actually 0:14:26.160 --> 0:14:30.560 converting the electricity into bits. On the sensor itself, it's 0:14:30.600 --> 0:14:35.840 got noise reduction capabilities, and so that means that it 0:14:35.880 --> 0:14:39.320 actually speeds up the process and it decreases the amount 0:14:39.360 --> 0:14:41.960 of space you need within a camera because all of 0:14:42.000 --> 0:14:44.240 those elements are found on a single chip as opposed 0:14:44.280 --> 0:14:52.720 to having dedicated chips for these these specific functions. Unfortunately, 0:14:52.760 --> 0:14:55.200 also reduces the amount of space it has for image 0:14:55.200 --> 0:14:58.200 capture because all that stuff is on the same chip. Yes, 0:14:58.280 --> 0:15:01.640 so that that you know, that's a downside, yes, so 0:15:02.080 --> 0:15:05.280 you that was one of the arguments again early on, 0:15:05.440 --> 0:15:10.680 was that c c D cameras could take sharper photos 0:15:10.720 --> 0:15:14.640 than CMOS cameras, and that you know, it's almost there 0:15:14.720 --> 0:15:18.680 was also an expense issue, right, c c D image 0:15:18.720 --> 0:15:24.200 sensors tend to be more expensive than CMOS ones CMOS. 0:15:24.320 --> 0:15:29.200 The process of manufacturer got so efficient that the price 0:15:29.240 --> 0:15:31.960 started to come down, and that that's why those are 0:15:31.960 --> 0:15:35.360 the sort of image sensors that you find in things 0:15:35.400 --> 0:15:39.160 like smartphones. You know, smartphones that have cameras tend to 0:15:39.160 --> 0:15:42.120 have CMOS sensors in them. They take up less space, 0:15:42.160 --> 0:15:44.920 they put out less heat, they take less energy to 0:15:45.040 --> 0:15:49.120 run um and they're very fast. So those are all 0:15:49.120 --> 0:15:52.160 the qualities that people who are having a who wants 0:15:52.160 --> 0:15:54.880 something in a nice slim form factor or if that's 0:15:54.920 --> 0:15:58.480 what's important to them. So yeah, C C D S 0:15:58.640 --> 0:16:03.640 image sensor might take a sharper quality photo in certain situations, 0:16:04.320 --> 0:16:07.080 but it's also going to require a larger form factor, 0:16:07.160 --> 0:16:10.640 and it does take more energy to run, and that 0:16:10.640 --> 0:16:14.040 that energy is going to also mean more heat. Yes, 0:16:14.200 --> 0:16:17.040 as we know, as electricity runs through a circuit, one 0:16:17.080 --> 0:16:20.040 of the by products is heat. We haven't figured out 0:16:20.040 --> 0:16:22.520 a way to get around that yet. It's just one 0:16:22.560 --> 0:16:27.240 of those one of those realities that it's uh um. Basically, 0:16:27.240 --> 0:16:29.520 it's inefficient enough where some of the energy is being 0:16:29.560 --> 0:16:32.440 converted to heat energy instead of you know what it 0:16:32.640 --> 0:16:35.480 is intended for. Right, Chris and I have a little 0:16:35.480 --> 0:16:37.800 bit more to say about image sensors, but before we 0:16:37.840 --> 0:16:40.000 get to that, let's take a quick break to thank 0:16:40.000 --> 0:16:51.720 our sponsor. So, so now we've got down to the 0:16:51.720 --> 0:16:56.400 the idea of these two different image sensors capturing uh 0:16:56.480 --> 0:17:01.520 information in different ways um, and the fact that over 0:17:01.600 --> 0:17:06.560 time both both types of sensors have developed to the 0:17:06.560 --> 0:17:09.480 point where the differences between the two, apart from the 0:17:09.480 --> 0:17:14.160 fundamental difference about how they collect information, have started to 0:17:14.160 --> 0:17:18.600 to diminish. Right, So that you can find some professional 0:17:18.640 --> 0:17:22.680 cameras out there now that you CMOS image sensors, whereas 0:17:22.760 --> 0:17:25.639 you know, a few years ago that was really unheard of. 0:17:26.240 --> 0:17:31.359 And you can also find some consumer cameras, especially in 0:17:31.359 --> 0:17:35.280 the cam Quorter realm, that are using cc D image sensors, 0:17:35.320 --> 0:17:37.880 which again for a while you just didn't hear about 0:17:37.880 --> 0:17:40.760 because c c D cameras were so expensive. It was 0:17:40.760 --> 0:17:46.000 pretty much reserved for professionals, you know, just consumers just 0:17:46.040 --> 0:17:48.399 didn't necessarily have the money to drop on something like 0:17:48.440 --> 0:17:54.000 that unless they were you know, one per centers. So yeah, 0:17:54.000 --> 0:17:57.920 it's it's it's it's still a developing thing and we're 0:17:57.920 --> 0:18:01.119 still seeing that kind of level out. But that and 0:18:01.160 --> 0:18:04.200 the two technologies do still exist. They coexist, so it's 0:18:04.200 --> 0:18:07.600 not like one has been abandoned on top of in 0:18:07.680 --> 0:18:10.960 favor of the other, although that tends to there there's 0:18:11.000 --> 0:18:15.199 usually someone predicting that every few years. Well sure, sure, 0:18:15.600 --> 0:18:17.360 um yeah. A lot of the research that I did 0:18:17.359 --> 0:18:21.400 for the podcast was from Teleedne Dolsa, which makes which 0:18:21.440 --> 0:18:24.480 makes both types of sensors, and they had some really interesting, 0:18:25.040 --> 0:18:29.399 uh comparative white papers and other information. If you're interested 0:18:29.400 --> 0:18:31.720 in getting into the depths of it, it got some 0:18:31.800 --> 0:18:35.239 of it got fairly complicated. UM. But basically they they 0:18:35.280 --> 0:18:38.800 had one paper they said that they're, uh that image 0:18:38.800 --> 0:18:45.440 sensors can be measured on basically eight different characteristics UM. 0:18:45.840 --> 0:18:49.800 And these were responsivity, you know, basically how responsive that 0:18:49.920 --> 0:18:58.119 the sensor is. Uh, it's dynamic range, uniformity, shuttering, UM, speed, windowing, 0:18:58.480 --> 0:19:02.080 and anti blooming UM. And you know, again this is 0:19:02.160 --> 0:19:05.960 kind of you know complex, but the the uh, it's 0:19:06.000 --> 0:19:10.360 kind of funny because the way that the image sensor 0:19:10.480 --> 0:19:14.040 captures information. UM. You know, depending on the type that 0:19:14.040 --> 0:19:18.920 you're talking about, they're not really uh, it's really application specific. 0:19:19.400 --> 0:19:22.160 UM some of them. Some of them really don't have 0:19:22.480 --> 0:19:26.119 that much difference over the others. Like, for example, UM, 0:19:26.320 --> 0:19:30.520 CMOS chips are known to be a little bit more responsive. UM. 0:19:30.560 --> 0:19:33.560 But c c D s are have an advantage in 0:19:33.640 --> 0:19:36.639 dynamic range. But basically they didn't say, you know, the 0:19:37.000 --> 0:19:40.000 this one chip is better than the others. They said, 0:19:40.040 --> 0:19:42.440 it has more to do with the manufacturing capability and 0:19:42.480 --> 0:19:44.720 whether the chip has done right and is used in 0:19:44.720 --> 0:19:48.000 their correct setting than it does UM, you know, for 0:19:48.119 --> 0:19:51.280 a particular type of technology. Right, and you were mentioned 0:19:51.400 --> 0:19:54.960 mentioning the fact that there are different shutters. In general, 0:19:55.280 --> 0:20:00.920 a CMOS image sensor uses a rolling shutter. Uh, there's 0:20:00.920 --> 0:20:03.199 nothing saying that it couldn't use the same sort of 0:20:03.200 --> 0:20:06.600 shutter that SEC the image sensor does, which is a 0:20:06.640 --> 0:20:09.679 global shutter. There's nothing saying that it couldn't. It's just 0:20:09.760 --> 0:20:14.600 that all the camcorders I looked at specifically, because this 0:20:14.760 --> 0:20:18.480 really plays more into video than than uh, still photography. 0:20:18.480 --> 0:20:22.800 Although there's some crossover between the two. Um it said 0:20:22.840 --> 0:20:25.679 that you could have a CMOS with a global shutter, 0:20:25.720 --> 0:20:28.399 it's just that you don't find those. So what's the 0:20:28.600 --> 0:20:31.199 between the global shutter and a rolling shutter? Well, a 0:20:31.280 --> 0:20:34.240 rolling shutter to me. And when I the first I 0:20:34.359 --> 0:20:36.479 read about this, the first thing I thought about was 0:20:37.800 --> 0:20:42.159 a copier or a scanner where the image sensor you 0:20:42.200 --> 0:20:45.720 put the document on the on the screen, you close 0:20:45.840 --> 0:20:48.880 the UM the top of the lid, and you tell 0:20:48.920 --> 0:20:50.199 it to go ahead and make a copy or make 0:20:50.200 --> 0:20:52.840 a scan of it, and the image sensor travels down 0:20:52.840 --> 0:20:54.720 the length of the document from the top to the 0:20:54.720 --> 0:20:59.480 bottom or what exactly, and and it is going you 0:20:59.480 --> 0:21:02.119 know from UM it's starting at a specific point and 0:21:02.200 --> 0:21:05.439 capturing the entire document as it travels the length of 0:21:05.440 --> 0:21:08.720 it and uh, you know, because it's going essentially line 0:21:08.720 --> 0:21:10.920 by line. If you think about that in pixel terms, 0:21:11.240 --> 0:21:13.040 is taking a row of pixels and then another row 0:21:13.040 --> 0:21:14.399 of pixels and then a nighte you know, as it 0:21:14.440 --> 0:21:16.640 goes down. Right, Yeah, I was thinking of it sort 0:21:16.640 --> 0:21:20.359 of the way television works. Yes, where it'll it'll you 0:21:20.440 --> 0:21:24.159 have a line by line from the top to the bottom. 0:21:24.280 --> 0:21:28.879 Um will ignore the interpalation part, otherwise we have to 0:21:28.920 --> 0:21:32.720 get really complicated. But anyway, the image is painted essentially 0:21:32.720 --> 0:21:34.640 on your screen from the top to the bottom at 0:21:34.640 --> 0:21:36.600 a rate that's so fast that your eye does not 0:21:36.680 --> 0:21:39.840 detect that. It looks like it's all simultaneously projected to you, 0:21:40.320 --> 0:21:42.280 but it's actually done line by line from the top 0:21:42.280 --> 0:21:43.760 of the screen to the bottom of the screen. Same 0:21:43.800 --> 0:21:46.560 thing with a rolling shutter. So when you take a 0:21:46.600 --> 0:21:50.199 photo or you're using a camcorder, let's stick with cam quorters. 0:21:50.880 --> 0:21:53.080 So if you're using a camcorder that has a rolling 0:21:53.119 --> 0:21:58.560 shutter type of image sensor talking cmos, uh, the the 0:21:58.640 --> 0:22:01.880 images being recorded from the top to the bottom over 0:22:01.920 --> 0:22:05.760 and over and over again. Okay, so uh with a 0:22:05.840 --> 0:22:08.640 c c D camera, it's a global shutter which means 0:22:08.680 --> 0:22:11.280 that it's capturing all that data all at once, Yes, 0:22:11.560 --> 0:22:14.400 sort of like film would. Yeah, so it's not it's 0:22:14.440 --> 0:22:17.720 not um you know, it's not something that's gonna be scrolling. 0:22:17.760 --> 0:22:20.240 It's all one image. So this means that the two 0:22:20.280 --> 0:22:24.600 different types of image sensors are also prone to two 0:22:24.680 --> 0:22:30.040 different kinds of flaws that can happen when you're using them. Well, 0:22:30.040 --> 0:22:32.560 of course, I mean that's that's like any other types 0:22:32.600 --> 0:22:35.520 of technology. Not everything is suited for every use, right, 0:22:35.920 --> 0:22:39.159 So let's say that let's i'll talk about the different 0:22:39.200 --> 0:22:42.120 flaws that you can find. C c D essentially has 0:22:42.440 --> 0:22:46.320 one type of flaw that you can encounter, which is 0:22:46.359 --> 0:22:52.600 called the smear effect. So smearing is let's say that 0:22:52.640 --> 0:22:56.160 you've got a a you're taking an image of something 0:22:56.200 --> 0:23:00.240 that has a bright light in it. Um Smearing is 0:23:00.280 --> 0:23:05.920 this effect where you sort of see the light. You'll 0:23:05.960 --> 0:23:08.600 see like a projection of light above and below it 0:23:08.960 --> 0:23:11.520 or you know it's that's that's why it's called smear. 0:23:11.560 --> 0:23:15.240 It's it's been extended beyond just a source of light itself. 0:23:16.119 --> 0:23:18.960 It's kind of like a halo effect, though usually it's 0:23:19.000 --> 0:23:22.439 more of at least in the samples. I've looked at. 0:23:22.480 --> 0:23:24.879 It's more of a vertical thing where it looks like 0:23:24.920 --> 0:23:27.639 it's almost like a ray of light that goes straight 0:23:27.720 --> 0:23:31.440 up and down the the the screen from the source. 0:23:32.320 --> 0:23:35.840 So that's one of the things that c c D 0:23:36.480 --> 0:23:42.280 image sensors can fall victim to, but not CMOS. And 0:23:42.400 --> 0:23:46.200 it's all because that global shutter exposes that image, the 0:23:46.640 --> 0:23:52.320 whole image simultaneously, and it's all gathering that light, and 0:23:52.640 --> 0:23:58.439 once the predetermined shutter speed for that global shutter has elapsed, 0:23:58.640 --> 0:24:02.800 it stops gathering light, turns that that entire exposure into 0:24:02.880 --> 0:24:08.040