Can UV filters help to reduce purple fringing?
UV is already well filtered by the lens and sensor but a UV 2A filter worked for this guy https://www.dpreview.com/forums/post/51786560
>>4479559>2A How does this nomenclature work?
>>4479555Why would adding some optically passive glass help the lens to focus colours on the sensor better than without it? If the CA issue was about coatings wouldn't they just coat the front element? And as far as I know, they use aspherical elements and special glass elements with high refractive index to correct for CA.
>>4479555Different wavelengths are refracted at different rates. Manufacturers sometimes use different materials to even it out. But more glass makes a lens slower. And with the magic of digital editing, the problem is solved by>>4479561
>>4479736What does it mean for a lens to be slower/faster?
>>4479746A faster lense (small F number) is easier for light to pass through. Therefore, more light gets through. And you can use a higher shutter speed, lower ISO, and/or tighter aperture for any given lighting situation.
>>4479748Also faster lenses generally have narrower focal planes. Which is how you get that blurry background effect.
>>4479564If it's transmission is similar to Wratten 2A, it's a UV block filter which cuts some blue too.See https://en.wikipedia.org/wiki/Wratten_number
>>4479752To add:Wratten 4 filter which blocks UV and visible violet might work more effectively for color fringing cause it is designed for that purpose. Digital should deal with color cast.I don't know where to get such filter...
>>4479755#12 Yellow is similar and #12A Light Yellow isn't as powerful but doesn't alter wb as much either
>>4479752Thank you. I understand now. That's the naming because Tiffen manufactures the filters under the wratten system.Here's some that I researched when it comes to clear filters:Tiffen 2A cuts out at 400-405mm. Tiffen 2E cuts out at 415-430nm. Only 77mm seems to be available.Kolari UV cuts out at 415nm. B+W 010 cuts out at around 350nm. They also have 486 UV/IR Cut filter, that is stronger and cuts at around 380nm for ultravilet, but I don't think that is sufficient.Zeiss T* UV cuts out at around 405nm.>>4479736>with the magic of digital editing,I want to correct the fringing for video, so this must be done optically foremost, the tools for video aren't that readily available and cameras certainly can't correct this type of longitudinal chromatic aberration automatically.>>4479572Lenses usually aren't designed to focus the ultraviolet spectrum well, and because the spectrum isn't clear cut some of it bleeds into the blue region. While glass will filter out UV-B (280-315nm) spectrum, UV-A (315-400nm) is left intact. Strong coatings make for unwanted color casts, so I guess even if lenses are coated to avoid ultraviolet, it's usually not that agressive so the violet-blue colouring doesn't get destroyed. The smaller the optical system, the more pronounced these aberrations are and with strong contrast between the subject and the background they can really ruin a picture. If you want greater filtering, the solution is to get a dedicated filter. That's how I see it.
>>4479786I long for the day /p/ realizes still photography is just a distraction from the real task of making cinema
>>4479790>cinefag>is a cine shill>is a fagWell, I guess we should have seen that coming
this is not OP btw. >>4479794
>>4479794When you graduate to film you'll realize that stills are just a playground for testing ideas. Still photography needs much less technical skill than film does, because manipulating every single detail is easy for a single frame but hard when you have 1440 frames per minute.
>>4479799This is why cinefags get are able to get it right on camera when stillfags have to postprocess and retouch everything btw. There's not that much stuff you can fix in post when making cinema, you just ice the cake. Polishing turds for hours is the domain of stillfags.
>>4479755>I don't know where to get such filter...I can only find it being used for telescopes, not something you can adapt to cameras.Here's an example. Obviously the poor image quality is due to the rest of the optics, but the filter does do some cleaning up.
>>4479555but this looks pretty
>>4479555Just paste the green channel's edges into the blue and red channels.
>>4479875Clever technique but I can't do that with video without lots of manual labour. That's why I think a filter would work better in that situation.>>4479843It doesn't look so good when the edge of the subject is so purple that it overwhelms the blue channel and it eats away at the shape.
>>4479760Wratten 12 is the minus blue filter. As blocks blue (and violet) when shooting false color IR film / digital imitation. (Can't find data of 12A if it's a thing.) Wratten 2A is pale yellow UV blocking filter, 2B blocks less, 2E blocks more, both also pale yellow.For transmission curves, check https://www.kodak.com/en/motion/page/wratten-2-filters/ (Posted this before: IR mod cheap p&s, W12 filter, flip channels)
>>4479916It's a Hirsch product, not part of the Wratten scale. It lets most blue through.
>>4480017 In that case It could be a good candidate.Likely any moderatel yellow could work as long its not strong enough to block all blue but strong enough to block purple.As authotrity of being almost completely ignorant of video color editing, I'd suggest getting white balance as right as possible in camera.
