![]() The article is titled Lens diffraction (as is the video it appears), the thing is, lens diffraction is independent of sensor size, resolution or pixel pitch. Source: ISO1200, images are screen captures from featured video You can find out more great content from Steve and Back Country Gallery on their site. There is afterall, more to diffraction than I’ve noted above, and the video does a really fine job of going through it all. See the video for more details, and visual representations of the information, which will help you visualize and internalize it with ease. If you understand these two points, you’ll ‘get it,’ and life, along with your images, will be better for it. So in a way, the sweet spot of your lens is the intersection point of lowest lens aberration and lowest diffraction. ![]() The lack of clarity and sharpness you’re acquainted with at your lowest f-stop is a product of lens aberration and not diffraction, and lens aberration, inversely to diffraction, tends to become less apparent as you stop down a bit. There’s this immediate association that the lower the f-number the more diffraction and softer the image is, but it doesn’t quite work that way. The second thing that often causes confusion is that most of us know from use and experience, reading about fast lenses or buying them, that most fast lenses aren’t as sharp wide open, say at f/1.4 than they are at f/5.6 or f/8. ‘In focus’ does not equal sharpness or clarity, and thus ‘more in focus’ does not mean ‘more sharp’ or ‘more clear.’ A larger ‘Zone of Focus’ (for example, as afforded with an aperture of f/22 vs a smaller zone of focus f/5.6) is often spoken in the verbiage ‘more in focus,’ and I believe this is where some amount of confusion comes in. One of the major points of contention and confusion often comes from two places the tendency for many people to associate zone of focus and depth of field as interchangeble with sharpness. This causes a loss of sharpness, and it’s this very thing that usually gets measured when we speak about finding the sharpest point or ‘sweet spot’ of a lens. It has to do with the way waves of light bend around obstacles/corners and mesh together, especially when traveling through a small opening. This is true in my experience as diffraction tends to appear as you stop down. He points out at the beginning that when most are referring to diffraction, they are referring to the softening of the image, particularly as you stop down your aperture. Steve Perry from Back Country Gallery does a good, concise job of explaining it in the video featured here. ![]() Which is a shame, because with a little clarity on the subject and the fuller understanding it affords, you’ll see the use of that knowledge apparent across the board you’ll be able to get clearer, sharper images, pick better lenses for certain scenarios, be more well equipped and know what to look for when actually purchasing a lens. (*Good God that was geeky*) – but it’s so often apparent to those who really understand it that many of those people are grossly mistaken about it. ![]() The low scattering and good image quality of reflective PVL enrich these functional devices and provide promising applications to novel foldable optical systems and waveguide-based wearable near-eye displays.Lens diffraction is one of those terms that fly out of people’s mouths at D4s speeds. Meanwhile, a simple approach is utilized to achieve 20 mm diameter and 16.5 mm focal length. In this paper, the PVL is theoretically evaluated and then three reflective PVLs at red, green, and blue wavelengths (R = 605 nm, G = 532 nm, and B = 450 nm) are fabricated. In contrast to traditional vertical spiral structure, PVL is based on patterned CLCs with a slanted helical axis. Here, a new off-axis reflective polarization volume lens (PVL) with f/# = 0.825, large aperture size, simple fabrication process, thin profile, circular polarization selectivity, and large diffraction angle is proposed. Furthermore, with the increasing demand for compact size in novel optical systems, reflective lens has advantage over the transmissive one because it can fold the optical path. However, because of the subwavelength-orientation requirement, it is challenging for liquid crystal lens to achieve a low f-number ( f/#) and large deflection angle simultaneously. Planar optics based on patterned cholesteric liquid crystals (CLCs) has attracted increasing attention owing to the self-organized helical structure and the ability to create arbitrary reflected wavefront through spatial orientation control.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |