Do scratches on filters affect pictures?

[ironringer]

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This is probably not the optimum group for this photography question, but since many of us USE our veteran Leicas, it is pertinent in the Collectors-Historica area.

Recently I put a clean, minty A36 filter (probably 1960s, since it has a chrome finish) on my newly-purchased, 1953 red scale Elmar, and shot a roll of Ilford FP5 film, to test both the lens and my recently-purchased black Leica III (picture attached). Although I am usually pretty careful with my equipment, I did put the camera in and out of my jacket pocket a few times, and it was "nude" without an ever-ready case. Unfortunately this careless treatment resulted in a couple of noticeable scratches right in the centre of the filter, of course (Murphy's law) in the worst place.

In your collective experience taking pictures, have you found that scratched filters affect the pictures, noticeably? Upon first review of my scanned film (.jpg files, 16base, typically 5 MB size), I don't see any effects in the centre of my pictures, but will examine them more closely to try to detect any distortion. Most of the pictures were taken at f5.6 (close to the "sweet aperture") and a few were taken at f4 aperture.

 

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[Dan Bachmann]

From my experience, unless they are major scratches (or cracks), the will only be noticed if the light falls on them in a way that makes them reflect light back into the lens. To reduce this use a hood.

 

[jankap]

The contrast of the picture suffers, somewhat.

By the way the center of the lens is not responsible for the center of the picture only. The whole lens surface transmits light to every point of the picture.

[jc_braconi]

This will not help you, but re think about the Murphy law... better on the filter than on the front lens, you are lucky.

[Herr Barnack]

Based on what I have read, if you are shooting into the light and your light source is illuminating the front element of your lens, that is when you could possibly have an issue.  Other than that scenario, your filter is probably okay. 

Years ago, I read a book by a nature photographer who did his work with a 4x5 camera.  He stated that his camera once fell forward when it was mounted to his tripod, causing what he referred to as "hideous damage" to the front element of one of his lenses.  He then went on to say that he still uses the lens and that the damage does not affect image quality in any way.  That is not the result that one would expect at all, but that was the man's account of his damaged lens.

Given the above, I would suspect that your scratched filter is likely not going to cause IQ problems. 

Edited January 19, 2020 by Herr Barnack

[Xícara de Café]

My experience with scratched lenses is that even when the lens is well shaded, bright objects in the scene can produce a halo effect in the image 

[pgk]

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Perhaps, maybe, depends. They may increase flare in certain conditions. Often you may notice no effect at all though. My filters are protective and not pristine but I see few problems in all honesty.

[Anbaric]

Assuming your filter is uncoated, I suspect that in itself is more likely to affect your pictures than minor scratches, since extra uncoated glass surfaces increase the risk of lens flare whenever there's a light source in the frame  This is why I prefer to use modern multicoated filters mounted with a SOOGZ (A36 lens to E39 filter) adapter - it's a pity these are now quite expensive. Of course the Elmar isn't exactly the most flare-resistant lens at the best of times, especially if it's also uncoated, so situations that are likely to produce flare always have to be handled carefully.

Edited January 19, 2020 by Anbaric

[ironringer]

Thank you everyone for your comments and suggestions. Yes, the filter did its job and protected the very nice red scale Elmar I was using. I understand that shooting into light sources will possibly create visible effects (flare, halo, reduced contrast) from deep scratches in a filter (or the lens). Certainly using a lens hood makes sense, as does the use of modern coated filters in adapters for old lenses. I shall take into account your advice and use that filter for its purpose; it offers protection as well as some contrast improvement.

Luckily I was using the veteran 1933 Leica III in Edinburgh and Loch Ness, with typically overcast & chilly weather, a good environment for flare-free photography. I was using Ilford FP5 for the first time, and like its results - good contrast, wide tonal range, and acceptable grain. I have a feeling that Montreal's remaining processing lab may not use the optimal developers and process, because the FP5 grain doesn't seem as fine as many users report. An example picture taken in an Edinburgh outdoor market is attached, with no sign of effects from the scratched filter: a 30% centre crop, exposure f5.6 at 1/40 second.

 

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[Pyrogallol]

FP5?

Do you mean HP5, I am using some at the moment instead of my usual FP4.

[ironringer]

Whoops, my mistake, I wrote too quickly without checking the film box. That is the first Ilford film I have used and I am not familiar with their names.

I will post a question in the film topic about "How much do different developer chemicals and processes affect the film grain?"

[Pyrogallol]

2 hours ago, ironringer said:

Whoops, my mistake, I wrote too quickly without checking the film box. That is the first Ilford film I have used and I am not familiar with their names.

I will post a question in the film topic about "How much do different developer chemicals and processes affect the film grain?"

Big question, I imagine you will get a lot of answers from the technical to the practical.

Though I use Rodinal and more recently Moersch Tanol, I would suggest a starting point of using Ilford developers with Ilford films, eg ID11, Ilfosol or Perceptol.

As far as the scratched filter is concerned, try taking the same picture, into the light, with and without the filter and see if there is any difference. Was the filter a plain UV or yellow/orange to add contrast to the sky?

Edited January 21, 2020 by Pyrogallol