Effect of using filter on rear element?

[andrew_herrick]

I have recently purchased a new Schneider 110mm XL lens. I am really nervous about leaving the glass exposed and am tempted to put filters on both the front and back. I plan to use high quality B+W filters. Firstly, will this degrade the image to a noticeable extent? I may want to stack another filter on the front, say a yellow or red. Will having three additional pieces of glass (albiet good ones) affect the image quality enough to worry me?

 

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Secondly, does anyone know if the rear element has the same problem as the front element, in terms of the filter touching the glass? Also can anyone confirm that the rear element has a 52mm thread? - I am not confident to measure it myself.

 

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Bob Salomon in another thread says that putting a filter on the back element causes focus shifts and image degradation if anything is on the filter. How big a problem is this? Would it be a problem with a high quality filter like B+W?

 

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If anyone has tried this could they please let me know how it went?

 

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Many thanks for your help!

[bob_salomon3]

Whether you use the highest quality filter made (Heliopan) or

another there will always be a focus shift = to 1/3rd the thickness

of the filter plus a filter on the back is going to reduce

performance more when it is on the rear since the lens has

already processed the image. When on the front dust, dirt,

fingerprints, smudges, etc. are far less likely to effect the image

then ones on the back.

[bob_moulton1]

Alas, I must cocur with the other posters. The rear filter will

degrade the image. BUT I have seen many images made by an artist who

always uses gelatin filters behind his images, and I can't see the

degradation in 24x30s. Like you I just purchased a 110 XL. I find I

can use Gels in a Kalt/Caulumet holder in front of the lens; I have

also used glass behind; the glass of lens and filter do not touch in

a rear mount position.

So far I can't see any image degradation no matter where I mount the

filters. I know it exists. And in some critical applications or if

one is sloppy it could caause problems, but so far...

[gary_jones2]

Bob is correct, however, I'd like to add my 1/2 cents. Although I'm

not a profession, I'm learning Architectural photography from one who

does it for a living. He uses Color Correction and Light Balancing

gel filters behind the lenses with excellent success. Even under a

loupe, the transparencies show virtually no difference in quality. In

keeping with Bob's statements;1) Focus with the filter in place. That

should compensate for the focus shift. 2)Clean dirt, dust,

fingerprints and smudges off of the filter as, hopefully, you have

done with the rear lens element and maybe even the front. As Bob

stated, contamination on the rear element will have greater

degradation than that of the front. I would venture to guess that

anyone desiring the ultimate in image quality isn't taking photographs

with contamination on any of the elements including the filters. I

realize the some location shooting may not have the best of

conditions. Another benefit of having the filters behind the lens is

that it is less likely get dust, dirt and fingerprints because it's

inside the camera. Ultimately you will have to decide for yourself if

the degradation is acceptable to you, so the best advice is to try it

both ways and check the results. Regarding the lens (110 XL), extra,

extra caution should be used mounting filters on the front, the lens

actually sticks out quite a bit and the filter threads are shallow. A

filter that also has shallow threads will touch glass-to-glass. I use

a 67-82mm step-up ring for my polarizer, to avoid vignetting and

glass-to-glass contact.(All other filters are behind the lens) And,

yes the rear filter size is 52mm. Good luck, Gary.

[neil_poulsen1]

Filters used on the rear are less likely to throw flare. (According

to Schneider.) I like using gels on the rear, and focusing with the

filter in place. I would discard a filter that was grimy, etc.

 

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I have a reducing lensboard. I've mounted a 4" Xenophon filter holder

(from Calumet) onto the back of this reducing lensboard in such a

from way that it does not interfere with mounting the smaller

lensboards. This simple device meets all my filter needs for color or

black and white.

[shambrick007]

How bout just being careful?!? Three filters??? C'mom.

[jim_noel1]

Three filters? NO. Waht are the other two, UV's to "Protect the lens?

That is camera store baloney.

Use a filter on the rear? By all means. If you want to use glass,

focus through it. I have use gels taped to the rear of the lenses on

my very large cameras for years. No degradation and no problems with

focus shift.

Jim