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Colour filters with C41 processed as b&w
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PostPosted: Tue Apr 02, 2013 6:26 pm    Post subject: Colour filters with C41 processed as b&w Reply with quote
Can I use old colour filters, ie yellow, red etc. like this. I am interested in processing a C41 film - Agfa Vista in caffenol. (Processing times suggestions will be good)

In the old b&w days I'd use a yellow, orange or even red filter to improve a sky. Will this work with colour emulsions developed as b&w?


PostPosted: Tue Apr 02, 2013 10:01 pm    Post subject: Reply with quote
I don't know, but thanks to the low cost of overall process, I'd say it's worth taking a test roll if you're interested.


PostPosted: Wed Apr 03, 2013 11:12 am    Post subject: Reply with quote
Interesting question. Since I do not dare to
say a definite Yes or No, how about running a
simulation in Photoshop?

a) Open a really colourful photo in Photoshop.
b) Add a Photo filter... layer, 100% Yellow, Preserve Luminosity.
c) Add a Black & White... layer, Default settings.
d) Tick Photo filter... layer on/off and observe the difference.

Then try different Photo filter/B&W settings.

At least it is an interesting exercise Smile


PostPosted: Thu Apr 04, 2013 11:40 am    Post subject: Reply with quote
Logic says it should behave the same way as a normal B&W film. Of course you still get the orange mask. (and some brown stain in caffeenol)

Why: (This is simplified, real film of course consists of more layers, but the principle is the same)

B&W Film is essentially a single layer, sensitive to the whole spectrum of visible light.

Color film consists of 3 layers, each sensitive to a part of the spectrum. The sum of those parts is again the whole spectrum.

So, if you e.g. use a yellow filter, you won't expose the blue sensitive crystals in the B&W emulsion / the blue sensitive layer in the Color Emulsion.

so, i'm quite sure that it will work as expected.


PostPosted: Thu Apr 04, 2013 5:48 pm    Post subject: Reply with quote
twinquartz wrote:
Interesting question. Since I do not dare to
say a definite Yes or No, how about running a
simulation in Photoshop?

a) Open a really colourful photo in Photoshop.
b) Add a Photo filter... layer, 100% Yellow, Preserve Luminosity.
c) Add a Black & White... layer, Default settings.
d) Tick Photo filter... layer on/off and observe the difference.

Then try different Photo filter/B&W settings.

At least it is an interesting exercise Smile


Well, yes this is an interesting excersice. I'll try this first. Whether or not it will work in real life (see belo) is another question. But always one to experiment and push boundaries I'll try both.

spoilerhead wrote:
Logic says it should behave the same way as a normal B&W film. Of course you still get the orange mask. (and some brown stain in caffeenol)

Why: (This is simplified, real film of course consists of more layers, but the principle is the same)

B&W Film is essentially a single layer, sensitive to the whole spectrum of visible light.

Color film consists of 3 layers, each sensitive to a part of the spectrum. The sum of those parts is again the whole spectrum.

So, if you e.g. use a yellow filter, you won't expose the blue sensitive crystals in the B&W emulsion / the blue sensitive layer in the Color Emulsion.

so, i'm quite sure that it will work as expected.


This was my initial thought before I placed the question on this forum ... but would it really work?

Of course there is only one way to find out! Do it!

Right I'm off over to the caffenol department to get a recipe. Must get some fixer. No recipes for that!


PostPosted: Thu Apr 04, 2013 7:31 pm    Post subject: Reply with quote
philslizzy wrote:

This was my initial thought before I placed the question on this forum ... but would it really work?

Of course there is only one way to find out! Do it!

Right I'm off over to the caffenol department to get a recipe. Must get some fixer. No recipes for that!


it shouldn't be worse than developing a non-filtered C41 film in caffenol Smile

Darkroom Printing it could be quite challenging i guess, but if you scan it, you're good.
Don't forget that color filters "eat" light, so if you use an external meter, you got to compensate for it.


PostPosted: Fri Apr 05, 2013 8:57 pm    Post subject: Reply with quote
spoilerhead wrote:
philslizzy wrote:

This was my initial thought before I placed the question on this forum ... but would it really work?

Of course there is only one way to find out! Do it!

Right I'm off over to the caffenol department to get a recipe. Must get some fixer. No recipes for that!


it shouldn't be worse than developing a non-filtered C41 film in caffenol Smile

Darkroom Printing it could be quite challenging i guess, but if you scan it, you're good.
Don't forget that color filters "eat" light, so if you use an external meter, you got to compensate for it.


I've printed from colour negs in the past in b&w, the contrast is low but it's doable. I assume the colour film devved in B&W chemistry will still have the orange mask. re the filter, I'll be metering thru it so no prob.

Just waiting for some fixer now.


PostPosted: Sat Apr 20, 2013 6:59 am    Post subject: Reply with quote
There are a LOT of discussions about this on APUG... do a search over there and you will find pages of stuff. I could go on a little about it but the people over there have 10 times the knowledge that I do on the subject
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