p.1 #1 · Testing UV filters in order to reduce (Lo)CA (Zeiss 55mm 1.8 & R4)
Hi!
I have posted a thread earlier wondering whether UV filter could help reducing LoCA on lenses, and decided to do some testing.
I have obtained 6 different (supposedly strong UV - within 400-420nm range) filters to test on my Zeiss 55mm 1.8 and R4:
1) B+W 415 (filter arrived but I realised it is fake) - there is no effect with this filter on the image as well;
2) Older Panchromar UV II - the filter has arrived and initial results seem to be positive;
3) B+W 415 Strong UV (original) / Should be Schott GG400 glass (Reply added on 10/05/2021);
4) Tiffen 2B (Tests added on 30/04/2021);
5) Custom Schott (GG420 glass) @ 2mm and around 418nm (Tests added on 14/05/2021);
6) GTX L41 filter (Tests added on 12/05/2021).
Below are 2 filters which have arraived and test samples for Panchromar. ...Unfortunately, it seems I cannot upload files here, so I will try to link another forum.
P.S. Panchromar provides good initial results, just WB is something you have to adjust probably. However, I generally initially like slightly warmer / yellower WB on this lens.
p.1 #3 · Testing UV filters in order to reduce (Lo)CA (Zeiss 55mm 1.8 & R4)
Panchromar UV II samples @ AWB (Note: Underwater AWB seemingly creates something closer to the No_Filter version but it is not tested here. Moving K slider couple hundreds in the LR makes similar image as well). You can see the settings on each file:
p.1 #6 · Testing UV filters in order to reduce (Lo)CA (Zeiss 55mm 1.8 & R4)
Well, aren’t all strong UV’s past 400nm considered ‘yellow’ to some degree. Panchromar definitely looks similar to Tiffen and GG420 at least in internet pictures. GG400 has a slight yellow cast as well.
Per definition I understand color filter to cut all other colors in the spectrum to some degree besides the one which it is meant to pass.
p.1 #8 · Testing UV filters in order to reduce (Lo)CA (Zeiss 55mm 1.8 & R4)
The allowed bandpass by various UV/IR cut filters can affect LoCA to a degree, it'll also depend on the quality of glass inside the lens and any coatings/degree of correction it has innately (obviously). When you break it down the LoCA you see in an image is caused by an inability of the lens to properly focus blue, green, and red wavelengths of light into the same spot/focal plane. So in-lieu of having a well corrected lens one option is to just block some of the blue wavelengths with a narrower UV/IR cut filter. With my telescopes I have varying degrees of LoCA correction and in one case I had to order a special UV/IR cut filter and Blue filter when imaging with it, it's made by a company called Astronomik and has a substantially narrower bandpass than my other UV/IR cut filters. I won't get into the nitty gritty, but you can read about the versions of the filters made by Astronomik here, I went with the L3 filter:
Basically the L3 filter allows from ~420nm to ~680nm, it did cut down on my blue bloating of stars (which is basically LoCA as the blue wavelengths of light are not as well focused as the red and green wavelengths of light) with my telescope.
p.1 #10 · Testing UV filters in order to reduce (Lo)CA (Zeiss 55mm 1.8 & R4)
realVivek wrote:
Though it does not have a question mark, I suspect that is a statement.
Assuming it is a question, there are modern L41 filters without any trace of yellow tint.
In any event, if something works for you, great!
I do not really know if it ‘works’ as a long time solution as I have concluded only initial tests with one filter. I am trying to do some wider range testing with multiple filters, and to share my findings with others to share knowledge.
P.S. Thank’s for directing me to L41-L42.
P.S.2. I generally prefered 50mm Zeiss 1.4, but as I have this lens at the monent I thougt I would do some testing.
The T&Y Foto L41 (fairly inexpensive, found on eBay) is actually a 420nm cut filter. Using it on a Sony camera body will cause color balancing issue. It cuts off violet.
p.1 #13 · Testing UV filters in order to reduce (Lo)CA (Zeiss 55mm 1.8 & R4)
EricofSLC wrote:
The allowed bandpass by various UV/IR cut filters can affect LoCA to a degree, it'll also depend on the quality of glass inside the lens and any coatings/degree of correction it has innately (obviously). When you break it down the LoCA you see in an image is caused by an inability of the lens to properly focus blue, green, and red wavelengths of light into the same spot/focal plane. So in-lieu of having a well corrected lens one option is to just block some of the blue wavelengths with a narrower UV/IR cut filter. With my telescopes I have varying degrees of LoCA correction and in one case I had to order a special UV/IR cut filter and Blue filter when imaging with it, it's made by a company called Astronomik and has a substantially narrower bandpass than my other UV/IR cut filters. I won't get into the nitty gritty, but you can read about the versions of the filters made by Astronomik here, I went with the L3 filter:
Basically the L3 filter allows from ~420nm to ~680nm, it did cut down on my blue bloating of stars (which is basically LoCA as the blue wavelengths of light are not as well focused as the red and green wavelengths of light) with my telescope. ...Show more →
Thank you!
Haven’t heard of those before.
In theory, if such L3 filter would be used on a normal lens / daylight situation - that would probably cause the same WB shift as stronger UV filters we are speaking about?
p.1 #15 · Testing UV filters in order to reduce (Lo)CA (Zeiss 55mm 1.8 & R4)
I try to standardize my UV filters across all lenses. Now I use the Zeiss T* UV's. Frankly I could care about anything other than the image and ease in processing the image.
p.1 #16 · Testing UV filters in order to reduce (Lo)CA (Zeiss 55mm 1.8 & R4)
It would be interesting to see comparisons with the WB normalized. Perhaps that would mask some of the effects of the filter but I'm curious how it might affect the color signature of the lens once white balanced properly.
p.1 #17 · Testing UV filters in order to reduce (Lo)CA (Zeiss 55mm 1.8 & R4)
B+W 415 arrived from KEH some time ago (I cant upload files to other forum for some reason today as well). It has very slight yellow cast at some angles and I do not really see a lot of difference for WB with / without the filter. Also, for the purple fringing there is really very slight effect. I can still notice it if I look carefully, but not a lot.
p.1 #18 · Testing UV filters in order to reduce (Lo)CA (Zeiss 55mm 1.8 & R4)
Back in my m4/3 days we had a problem with Panasonic lenses on Olympus body where for instance lights in a night scene turned bluish and other similar problems, also in daytime shots.
This was due to Panasonic having weaker UV-filters on their lenses and stronger UV-filters in their filter stack in front of the sensor, and Olympus instead had weaker UV-filters in the stack and stronger in the lenses.
The remedy was to use Tiffens UV2A Haze filters and by that much of the problem went away.
