Canon Lens Design
Alright, folks, let's build a lens. Everyone grab your glass and we're gonna build a lens together. Wouldn't that be fun to do in here? Okay, so let's let's just theoretically build the lens. What do we want out of a lance? Okay, what do you think would be important to have? Let's do some questions. Let's let's hear some feedback. About what? What do you think we should have in a land? Somebody pick up a microphone and let's just pipe pass the microphone down the line and just think of something that we need toe part of the lens. What's important in a lens? Grab the mike. What do you think is important in the lens? The glass, the glass? Okay, let's hear some. Something else. Three. Overall construction. Whatever. It's cased in that needs to hold it all together. Good, solid construction so doesn't fall apart. Yeah, OK, it's pass the mic down. Just what else? What do you think is important to a lens designer? What do we wouldn't What are we trying to create NEDA holed up in weather? Oka...
y, maybe a weather, whether ceiling on there might be important. It's another issue might think about the overall quality of the lenses, overall quality, maybe the resolution of the lands. Okay, so let's take a look at some of the things that are important. Great resolution. We want a lens that's really sharp, right? Isn't that what people look at? How sharp is the lens? But that's not the only thing about contrast. You won't have good contrast in Linz. You want your blacks black and your whites white. You want the car, and you're gonna see some photos where I'm gonna show low contrast. They don't look very good. You wanna lands. That has really accurate color that represents the color that you're photographing. You don't want to put a purple lens in there and have everything purple. It's got a really refract and do the right things with the color distortions. We talked about distortions. You don't want things throwing things out of shape. It needs to be really project a smooth, straight lines. You would like to produce the smallest. You don't you want a huge Nobody wants to carry around a huge lens, so let's design it as small and as compact as possible. We want to make it is lightweight is possible. Let's put the fewest number of lenses in there so that we could make this a lighter lens. But what if more lenses make it better quality? And then we get into a real debate around the roundtable about how we design our lands. We want it simple, the use. We also want it simple, the bill, because that's gonna make it lower cost. Maybe we're gonna make more money on our lenses if we could build a lens for 20 bucks and sell it for 1000. And so these are just some of the ideas that go into How do we make a lens and what are some of the compromises? So let's go through some of these resolution resolving power to see fine detail. And so we need pretty high resolving power lenses thes days. But you know what? They can get better. They can be better than they are today, but we don't need them because our sensors are limited to X number of megapixels, whatever that happens to be. And so there will be different lenses that have different resolving power and one of the things that has changed in the last 25 years of my photography is that lenses have needed to get even better because our digital sensors are better than the film that I shot when I started. Photography, contrast ratio efficiency in transmitting light with minimal reflections. And so imagine there is an area of blackness, maybe one of these shadows, and you have a lens that's bouncing light all around in there. What's gonna happen is a little bit of light is gonna hit that black area, and it's gonna lighten it up. And so we want as contrast e of light coming through the lands and this a little bit different when we get to actually printing are images and working with them. But through our lands, we want high contrast. We want our blacks black and are whites white. As I mentioned, you want light to come straight through the lens. You don't want it to be bouncing off these glasses and having this light hit areas that are not supposed to have light. And that's what happens in getting low cost low contrast lenses is that the light's bouncing around and it's not hitting toe where it's supposed to hit flair issues. What if this person points our lands in a bright light source. What's gonna happen? This isn't good. We don't want this to be ruining our photographs. And this depends on the type of glass that we put in there, the coatings that they have on in the shape of the glass diffraction. We talked a little bit about this before. So designing the lens, the aperture both of these have an impact on exactly what happens with that light as we squeeze it through. Maybe a small F 16 opening the materials that they use in the aperture can affect what type of scatter you're going to get and what type of diffraction it's gonna look like. Chromatic aberration. This is a big bugaboo for a lot of people, and a lot of lenses have some fairly bad chromatic aberration, a distortion when colors do not converge at the same point. And this often happens when you're shooting a scene that has a very bright background with a solid object in front of it. And so if we take a close look at this, if you look really closely, you'll notice a red line on the underneath side in kind of a bluish teal colored line on the upper side of those beams, and this is light that is coming around those beams, and it is not hitting the sensor in exactly the same spot. Now. Chromatic aberration just looks bad. Nobody likes this, but it is correctable in software afterwards. So, for instance, if you have light room, you could go in there and they have little chromatic sliders that you can choose which color you want and how much you want to try to fix it. And you can pretty much eliminate this. But it's a little bit of a hassle in order to eliminate, because sometimes you need to get picture by picture to adjust the sliders to get rid of it. And so it is correctable. But it be preferable if our lenses did not have any chromatic aberration, coma or co Matic aberration, a variation in the magnification over the entrance pupil. All right, and so this is gonna manifest itself if you do nighttime star point photography. So I'm down at the very large array, shooting a nighttime shot with a very high quality lens that is excellent for this type of work, but it's not perfect. If you look at some of these stars, they kind of look like Saturn because they kind of blown out and they kind of look like a comment. And so this is a little bit off coma in this lens. I would prefer it didn't have it. It's a small problem. There really isn't another lens that doesn't much better job that works on my camera, so I live with it. And there's not much in the way to correct that. In post astigmatism light rays of two perpendicular planes having different focus points. So as light from one point passes through different parts of the lands, they don't meet up in the right spot, and it's gonna be a little bit of blurriness. And that's just something that it's just gonna be blurry. It's just not gonna look good. And so they try to correct for that, with the right shape to the lenses distortion. We talked a little bit about this before. Barrel distortion and pin cushion distortion. It's on all of our lenses, just fortunately for most of them, it's not that bad of a problem. Some lenses are much worse than others, and there's many websites and people who test lenses that will tell you exactly how bad it is. But this is something that could be corrected in post. Granted, you are pushing pixels around, which is affecting your image quality, and you sometimes lose a little bit on the white angle side cause you have to push things in, um, and then crop it a little bit because of the nature of barrel distortion. And so we don't want distortion, but we get it a little bit. Vignette. This is a dark immune of the corner. Both of these images show you darkened corners of the image. It's preferable if you don't have this in many cases. But a lot of photographers, myself included, will add it to a photograph just as an effect. And if this seems somehow familiar, let me share with you a couple of family photographs, and these are a couple of the oldest photos in my family now on the right here we have Amos and Irving, and Irving is my great grandfather, and Amos is my great great grandfather, and you'll notice that picture has been getting, as does my great great great grandfather Jesse and so the lenses did not let in as much light, which is why we don't see the detail. We don't see the sharpness in the corners. In fact, if you remember those really old photographs, Ah, lot of them came in ovals because the corners were so bad on those images, there was there was nothing to show their And so that's why they were oval and why we have squarish images that go all the way out to the corner. There I had mentioned Focus breathing in the city section, and so when you focus with a movie camera, there is very little change in magnification, and I try and remember which lens I used for this example. I don't recall it might be the 100 micro. So this is a video. So let's get this video started here now watches I change the focus towards the foreground. You'll notice that there's a magnification and framing change as I move this focusing back and forth when you're shooting movies. You don't like this because you're trying to keep a really tight frame for still photographers. It's not that big a deal. It's a little bit of an issue when you're doing macro photography, you change your focus, and all of a sudden you need to move your tripod forward or backward. It's preferable if a lens did not have focused breeding, but they all do. To some degree. Okay is the quality of the out of focus area, and this is more a matter of personal opinion. But there is a lot of consensus that people have about what's generally good and what's generally bad. And so, ah, good Brok will have a nice, soft out of focus and a bad bo. OK, we'll kind of have a jittery focus. It's more clumped up, and it's not as smooth across. Remember when we're talking about the aperture, the shape of the aperture. Having a circular aperture will yield a highlight that looks like this good Brok highlight its rounded, whereas the bad Okay, you start seeing the shape of the aperture in the lens, and that's why we want our rounded apertures. So there's a lot of stuff going on in the design, and finally, there's the construction issues. How do we build this lens? What sort of parts do we use? Plastic parts for metal parts, metal parts or more expensive. They're harder to work with, but they last longer. They're better. Call Saul the construction. What size of focusing ring do we want to put on it? How much is that gonna cost us? And so this has a lot of impact on the final product that you get. So those are some of the things to think about what's going on behind the scenes in the design of your lens. Now, toe actually build a lens. You start with these powdered compounds which they mix. There's chemist that know how to mix exactly up to 100 different ingredients in this big vat of chemicals are big. He looks like a pile of dust is what it looks like san. And this can cost upwards of $1000 per kilograms. So this could be some very expensive materials that they've had to mine out of the earth and mix to get just right. And if you want to know how to make a lens, this I'm not gonna read through these, But this is kind of the general process so that you need to go through in making the lands. It's not just melting sand and suddenly you got yourself a nice lands. There's a lot of things that go into the process. There's some great videos on YouTube. If you want to go on YouTube and type in how lenses made or how Canon makes lenses, Canon has a nice three part series on how they make lenses that set about 30 minutes that show you going through this entire process. What it looks like. It's very interesting. I'd love to go to the factory and see that. Then we needed to figure out How many elements are we gonna have in there? What sort of material are we using? What's the order and how are these lenses all grouped? Because we can make any particular lands in a 1,000,000 different ways, according to what we want to do with these kind of factors in here.