C41 colour film with yellow filter

Asha

Asha

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Asha
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Quick question:

What effect will a yellow filter ( designed for adding contrast to b&w film) have on an exposure taken using C-41 colour negative film?

Thanks
 
Yellow colour cast at a guess. A red filter gives a red cast - I've done it (deliberately, I should add).
 
That’s what I thought...... asking for someone who’s just asked me who has been out today and exposed a roll of colour film but forgot that he still had a yellow filter screwed on the front of the lens !
 
Ive recommended scanning to monochrome and adjusting curves as necessary to try salvage whatever he can.
 
I've never tried it, but given that colours aren't pure, and yellow is a mixture of two of the primary colours, it might be possible to salvage something in Photoshop. I know that even a blue cap isn't a pure black even in the red channel in Photoshop. One way of looking at it is that the exposure was made in a very warm artificial light...
 
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Not quite as pronounced a cast as shooting daylight film under tungsten lighting. Possibly recoverable by scanning and correcting a cast but that will give slightly odd colours (not sure since I "my friend (!)" who did it on half a roll the first time I he used a rangefinder binned the negs and prints in disgust about 40 years ago!!!)
 
Being a tog who now shoots exclusively monochrome, these issues are automatically avoided, not that it stops me making other stupid mistakes :banghead:
 
Yes it will give a quite severe cast which will not easily be removed. I have not done it myself, but I used to work part time in a mini lab and the filtration needed to correct a similar error was almost at the end of the scale and even then it wasn't right. The yellow light that passed through the lens after being reflected off various different coloured parts of the subject being photographed, some reflected less yellow than others that gave a problem called 'crossed curves'. These were more like criss-crossed curves. The nearest example I can think of is if you use colour neg film with a yellow filter and photograph daffodils with a blue, or green, or red background the flowers will be (almost) OK, Red is not too bad, but the others will be well off the mark. Try to correct it and the colour shifts at the other end of the spectrum.

On another score I have deliberately used a 8x red filter on the front of a Nikon Digital SLR. The resulting images are of course red, but when converted to B&W using Photoshop the resulting IR effect is quite outstanding. Better than PS's own black and white, IR converter
 
It's certainly possible to make a mistake with colour film by inadvertently using a filter, but with black and white the reverse is possible. I have a photograph of a rusting metal barge on a riverbank, with wonderful cross hatched shadows. Ruined because by not using a filter the reddish barge merged with the river behind, meaning the outlines were blurred.
 
StephenM said:
I've never tried it, but given that colours aren't pure, and yellow is a mixture of two of the primary colours, it might be possible to salvage something in Photoshop. I know that even a blue cap isn't a pure black even in the red channel in Photoshop. One way of looking at it is that the exposure was made in a very warm artificial light...
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The idea of primary colours is very much to do with how the human eye works rather than 'pure' colours.
In the case of filters most yellow filters are long pass designs that just blocking shorter wavelengths (generally UV, violet & blue).
One of the most common yellow/orange light sources is MUCH closer to being pure colour than most other common light sources. Low pressure sodium lights (still fairly common in street lights) give nearly all their light in two very close wavelengths known as the sodium D lines at 588.9950 and 589.5924 nanometers. The first of these is responsible for around 70% of the total light output.
Primary colour lights can be mixed in the right proportion to give the same visual appearance to normal humans (they will probably look quite different to people with 'colour blindness', or many other animals that can see colour).

Used with colour film most yellow filters will effectively block blue, making blue shades considerably darker, but also removing the blue from white light.
If a purple is produced by a mixture of blue light & red light it will make the colour look much more red (blocking all the blue & hardly any of the red), but if the purple a more monochromatic source (perhaps 400-450nm) it will block it entirely.

Warming filters share some similarities to long pass filters but tend to have much more gradual transitions.
 
Oops
 
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damn double oops
 
Asha said:
That’s what I thought...... asking for someone who’s just asked me who has been out today and exposed a roll of colour film but forgot that he still had a yellow filter screwed on the front of the lens !
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I've done it, many years ago. If memory serves, it was a pale yellow filter. The results were not good, but no worse than when I've scanned some 1970s colour films!

Assuming you didn't mean XP2, I'd suggest scanning as black and white anyway.
 
Are those fish filter feeders? :exit:
 
If you use an old lens e.g. Pentax tak you have a mild yellow filter (if not used for a while) because of radioactive thorium in the glass and to clear the yellow just point the lens in the sun for a while, I never noticed any problem with colour film (used not so long ago) as if it did affect the colours......was removed by scanning.
 
I have a Minolta 28mm F2.8 MC lens with a Thorium element which has quite a strong yellow colour, not just a tint, so use that on occasions for B&W and don't use a filter. The cloud rendering is very good. I have another which is an MD version so I am not treating it to UV. It is VERY sharp which I believe the Thorium was used to enhance the performance.
 
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h'mm thought of another "old age get out of a situation card":- my brain has been affected by using a radioactive lens for 60 years o_O :D
 
I seem to remember around 1977/8 had a very long and in depth article about this and the use of Thorium elements in Canon lenses. I think one of the issues was Thorium glass was easily damaged by sunlight???? It is so long ago I cannot remember the full details, but it was definitely in the AP magazine.
 
darkroom12 said:
I seem to remember around 1977/8 had a very long and in depth article about this and the use of Thorium elements in Canon lenses. I think one of the issues was Thorium glass was easily damaged by sunlight???? It is so long ago I cannot remember the full details, but it was definitely in the AP magazine.
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I think you're miss-remembering it. Thorium glass gradually discolours, and sunlight treats the yellowing restoring it's original clear appearance. Due to this lenses with thorium glass are often deliberately exposed to sunlight beyond normal usage & there are no reports that damages their performance.
 
darkroom12 said:
I seem to remember around 1977/8 had a very long and in depth article about this and the use of Thorium elements in Canon lenses. I think one of the issues was Thorium glass was easily damaged by sunlight???? It is so long ago I cannot remember the full details, but it was definitely in the AP magazine.
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That doesn't seem logical as why would lens makers produce a lens that was ruined by sunlight...anyway my old 55mm Pentax Tak can still produce sharp pictures after 60 years and I'm mainly a sunny weather shooter, although there might be some truth in it as compared to a modern analogue 50mm it is not as sharp now if pixel peeping and only realised this after buying modern 50mms and seeing the results esp using a later 50mm Minolta lens. But then that's the same with quite a few old and newer analogue lens comparisons.
 
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