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I very recently bought an Olympus Pen-F digital body. The primary reason for this selection being my long-time satisfaction with my film Pen-FT, now with broken mirror return, for which I have a collection of lenses and the fact that, with an adaptor (I selected the Fotodiox PenF→m4/3 adaptor as Olympus does not offer a native adaptor), I could bring my lens collection back into service. All the lenses retain their skylight filters from my film days. I am entirely comfortable shooting manual focus/aperture/shutter.

With the few trial photos I have taken with the new camera body, so far I am disappointed with the images. Under natural lighting, nicely exposed images have a brownish cast to them. Why am I getting this brownish cast?

  • Are you sure the pink cast from the skylight filters isn't part of your brownish cast? How have you set white balance? Do you know about focus peaking, and magnification as focus aids? Nobody has split-circle prism collar focus screens any more. Related: Can I use lens brand X on interchangeable lens camera brand Y?. – inkista Feb 14 '18 at 3:20
  • Thank you, inkista, I had not thought of the skylight filters as a possible cause, having simply taken them for granted ever since I put them on back in my film days. I'll try taking them off. I had better do some research about focus peaking, and magnification as focus aids. – Ted Feb 14 '18 at 6:16
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    @inkista Thank you for joining my windmill-tilting quest to have meaningful titles on all questions. :) – mattdm Feb 14 '18 at 20:44
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    @mattdm :D :D :D Jinx! (And what do you mean I'm joining you? You're joining me! I've been doing this for ages!) – inkista Feb 14 '18 at 20:45
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    @Ted Can you post a sample? – mattdm Feb 14 '18 at 20:45
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The three most probable causes I can think of for the brownish tint would be:

  1. That you're using Skylight filters, instead of something color-neutral, like a UV filter.

  2. That you are shooting JPEG and you haven't set your white balance correctly.

  3. Thorium or some other issue has caused your lenses to brown over time.

White Balance

The camera is actually doing some digital processing on the sensor data to create your image files. And if you are shooting JPEG files, it's not only compressing the image data, it's also using settings in the camera, such as your white balance setting to create the file.

The white balance can be set to offset common color-cast issues, such as shooting under incandescent/tungsten lighting giving an orange cast. This white balance processing would add blue to the image to try and shift the colors back to something more neutral.

You could consider shooting RAW or RAW+JPEG, to give you a chance to "reset" the white balance in post-processing.

Thorium (aka, are your lenses radioactive? :-)

Many lenses made from the '40s to the '70s use thorium glass elements. The Pen F 40/1.4 is one of them. Thorium is mildly radioactive and browns or yellows the glass as it ages. This tinting can be reversed by dosing the lens again with UV radiation to reverse the decay. Simple LED desk lamps have more than enough UV to do this, as does putting the lens in sunlight. But obviously, you want to take care you don't use direct sunlight in such a way that your lens becomes a magnifying glass burning a hole in something, or that the lens heats up enough to affect any plastics/grease/adhesives in the lens.

See: http://camerapedia.wikia.com/wiki/Radioactive_lenses

  • Thank you @inkista, The white balance is currently at the camera's default, Auto. I was completely unaware of the thorium issue and its browning of the glass itself. I purchased all lenses before 1972. I just experimented, looking through the lenses off the camera and without their skylight filters, viewing to a piece of white paper. My 25 mm 1:4 is clean, the paper appears just as white through the lens as without the lens; my 42 mm 1:1.2 (my favourite, most frequently used while my old Pen-FT still worked) shows definite browning of its view of the paper; my 50 to 90 mm zoom 1:3.5 shows – Ted Feb 16 '18 at 9:51
  • browning as well but not as strongly; my 135 mm 1:3.5 shows a hint of browning; and my 2x teleconverter also shows a hint of browning. How long an exposure to UV should I give to hope to reverse this browning of the glass? – Ted Feb 16 '18 at 9:52
  • @Ted Might be better to ask about using UV to reverse the tint as another question. But in the meantime see: rangefinderforum.com/forums/… – inkista Feb 16 '18 at 22:00
  • Thank you @inkista, that link gives me a good idea of what to plan for. – Ted Feb 18 '18 at 9:26
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Skylight filters were meant to be used with film when shooting longer distances under natural sunlight that tended to tint everything too blue. They were also used to warm the blue tint of shadows outdoors in daylight, particularly with color slide film that could not be color corrected after the fact. They were another option from color neutral UV filters, which filtered out the UV light so it couldn't interact with the chemical emulsion of the film. Rather than filtering the UV portion of the spectrum that causes this color shift, skylight filters are color correction filters that cut blue light and shift the overall color balance a bit towards somewhere between magenta and orange to offset the bluish response of color film to UV light scattered in the atmosphere. Some skylight filters also had a UV filter layer.

Photographers shooting film could choose either a UV filter or a skylight filter. Using both at the same time would eliminate the influence of the UV light on the films chemistry and add an orange/magenta cast to the color of the light striking the film.

Digital cameras have UV filters in the internal filter stack in front of the sensor that do the same thing as a UV filter on the front of the lens did in the film days. Including a skylight filter on the front of the lens when shooting with a digital camera will add a color shift that is not needed to counteract the effect of UV light on color film. If you save your images in raw format you can include a reciprocal color shift in post. But by using the filter to attenuate blue-green light and then attenuating the opposite side of the color wheel in post your are reducing the overall sensitivity and efficiency of your imaging system. There are also a few rare examples of digital cameras that have external white balance sensors. The Olympus E-5 is one example. Since the filter would not cover this sensor the camera would not compensate for the color cast added by the filter.

  • Thank you @Micheal, I am taking the skylight filters off all my lenses and am considering inkista's explanation about thorium. – Ted Feb 16 '18 at 10:12
  • @Ted It's probably a bit of both. The skylight influence will be a bit pinker, the thorium influence will be a bit oranger. Combined they will add a brown tint. AWB doesn't always deal very well with color casts if the highlights are bright enough to still saturate all three channels. – Michael C Feb 16 '18 at 10:47
  • I would agree, @Michael. It must be the combination. Filters off now to try the UV. – Ted Feb 18 '18 at 9:29
  • Is uv filter a must? – Michael C Feb 18 '18 at 10:01
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    No, @Michael, not UV filters, the UV treatment inkista tells me about, above. – Ted Feb 20 '18 at 10:01

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