Canon® Lens Shape
So we got our glass compounds. We've got the glass that we got the type of glass we're going to do. Now. Once we have this, we need to shape it. Alright now most lenses are going to be shaped into a spherical, rounded type element, and that works out well for most lenses we can you do that most of the time and it's going to come out fine, but from time to time, depending on the chemical compound, depending on the way the light travels through here, our red, blue and green points of light don't end up in the right area. How do we fix this? Well, one of the solutions is to create an a spherical element that has a non perfectly smooth exterior. It's. It is smooth but it's, not a rounded in the way that a spherical it forms a sphere, all right, and by doing that, if they do it just right, they can fix this problem. So this could potentially reduce spherical aberrations astigmatism. And it can also reduce the number of elements which means we can make a smaller lands. 00:01:04.1 --> 00:01:0...
7. You'll find these in wide angles lardo, large aperture 00:01:07.08 --> 00:01:09. lenses and compact zooms where they're really trying 00:01:09.78 --> 00:01:12. to reduce the size of the lens quite a bit, 00:01:13.65 --> 00:01:16. and so there's a long list of lenses that are using 00:01:16.36 --> 00:01:17. this as spherical glass 00:01:18.7 --> 00:01:21. and as I say, I'm not involved in the process of making, 00:01:21.58 --> 00:01:24. but I would think polishing a spherical element is 00:01:24.78 --> 00:01:27. a whole lot easier than an astrological one because 00:01:27.61 --> 00:01:31. the types of machines they have will take like forty 00:01:31.25 --> 00:01:33. lenses in them and just be kind of rubbing them all 00:01:33.76 --> 00:01:36. around, smoothing them all up. But when it comes to 00:01:36.34 --> 00:01:38. ask miracle it's a whole different system that they 00:01:38.32 --> 00:01:40. had to develop in order to work with these types of 00:01:40.19 --> 00:01:43. glass elements, and so there are different types of 00:01:43.19 --> 00:01:46. hysterical elements ground and polished, that sounds 00:01:46.13 --> 00:01:50. pretty good to me molded glass not quite is good, 00:01:50.21 --> 00:01:52. so they just kind of form it in that shape rather 00:01:52.55 --> 00:01:55. than grinding it down. And then there are precision 00:01:55.01 --> 00:01:57. molded plastics that they will use and that's more 00:01:57.49 --> 00:02:00. likely to be found in some of their point shoot and 00:02:00.37 --> 00:02:03. smaller in cameras. And so they are technically plastic 00:02:03.32 --> 00:02:05. lenses in there, which some people are very concerned 00:02:05.61 --> 00:02:08. is that a glass lens or plastic lands? Well, you know 00:02:08.01 --> 00:02:09. what with that they could do with plastics, they could 00:02:09.77 --> 00:02:11. make him as good or better than standard glass 00:02:14.72 --> 00:02:17. d o stands for diffraction optics and it's only used 00:02:17.91 --> 00:02:21. in a couple very unique very special lenses from canada 00:02:22.42 --> 00:02:25. so one idea says we're all designing our lenses right 00:02:25.72 --> 00:02:29. is excuse me what if we just made everything smaller 00:02:30.32 --> 00:02:32. I want it that I mean okay here's our big lands let's 00:02:32.82 --> 00:02:35. just make the lens and all the lens elements smaller 00:02:36.06 --> 00:02:38. what's the problem with that can't we just reduce 00:02:38.03 --> 00:02:42. everything well if we do that it's quite possible 00:02:42.49 --> 00:02:46. that our light rays once again do not end up at the 00:02:46.36 --> 00:02:49. same point and we're not getting sharp focus so nice 00:02:49.48 --> 00:02:51. idea just reduce everything make everything half the 00:02:51.47 --> 00:02:53. size and it will work doesn't always work that way 00:02:54.35 --> 00:02:58. so another solution that they found was a diffraction 00:02:58.67 --> 00:03:02. script structure and they found that this was fairly 00:03:02.44 --> 00:03:05. good and they could use this to focus the light in 00:03:05.52 --> 00:03:08. on the sensor and get a pretty good image out of it 00:03:09.02 --> 00:03:12. but it wasn't perfect perfect some of the light dispersed 00:03:12.2 --> 00:03:16. off to the side okay how do we fix this out and what 00:03:16.05 --> 00:03:18. their currently using is they're using a dual layered, 00:03:19.42 --> 00:03:22. multilayered refractive structure that corrects for 00:03:22.66 --> 00:03:26. these problems redirects light properly and and they're 00:03:26.55 --> 00:03:29. able to reduce the size of the lens significantly 00:03:29.65 --> 00:03:34. in some cases in order to get a nice sharp image so 00:03:34.51 --> 00:03:37. they designed a four hundred millimeter f four lands 00:03:37.11 --> 00:03:39. and they said you know what this thing is going to 00:03:39.07 --> 00:03:41. be? Thirty one point seven millimeters in length they 00:03:41.52 --> 00:03:43. know the stuff I had a time exactly what they're going 00:03:43.53 --> 00:03:47. to need but we want to design something that is significantly 00:03:47.05 --> 00:03:49. smaller with these new optics and this is how they 00:03:49.52 --> 00:03:53. came up with their four hundred d o d fracked of optic 00:03:53.41 --> 00:03:55. lands they just introduced their second version of 00:03:55.99 --> 00:03:58. this and if you compare what a normal four hundred 00:03:58.27 --> 00:04:02. is versus the dio it is eh big savings in size and 00:04:02.36 --> 00:04:05. in weight so twenty seven percent smaller thirty one 00:04:05.6 --> 00:04:08. percent lighter in size very nice thing to have 00:04:09.84 --> 00:04:12. you will also find this in another lens that they 00:04:12.18 --> 00:04:14. have they have a standard seventy two three hundred 00:04:14.6 --> 00:04:18. lands pretty typical it's fourteen centimeters almost 00:04:18.11 --> 00:04:22. six inches in height they do have a triple layer dio design in their seventy two three hundred d oh let's thirty percent smaller eighteen percent lighter this is all well and good but life is not perfect in the world of deal because of the way the lenses are cut he will sometimes get flare issues that don't look like a flare from the normal ends and they can't just implement this on every single lens it just doesn't work out which is why we don't see it on everything out there there's on ly this compact zoom there's the old four hundred and the new four hundred which by the way is much sharper than the old one that has this d'oh technology they kind of let it lie dormant for about ten years. And I kind of wondered if they were going to do anything more with it. Because, optically speaking, the four hundred and the seventy two, three hundred are among the weaker cannon lenses when it comes to sharpness and overall image quality. And so it's. Not a perfected technology. But I will have to say that the four hundred f four and all the image tests that I've seen is pretty darn phenomenal. It looks really, really good. And so maybe they have kind of figured out any of the little bugs in there. Because it's it's looking really good these days on that latest lens, at least. So that's, a special lens designed for those lances.