Special processing for C-41 low light tungsten shooting
Generally, a guideline to expose daylight-balanced color neg film in tungsten (low color temperature) light is to overexpose with (almost) the filter factor of corresponding filter, even if the filter is not used, to place all of the R, G, B exposures on the linear part of curve. If this is not done, blue ends up on the toe, having lower contrast and lost definition in shadows, creating color crossover.
This can be quite problematic, because usually tungsten-lighted interiors also have a low level of light, where we need higher ISOs, so exposing a 800 ISO film at ISO 400 or even 200 to get good results may not be possible.
Push-processing C-41 works at some level by boosting contrast of exposures placed on toe, but, now I'm chasing for a method to "push" process the blue-sensitive (yellow) top layer more than green and especially red-sensitive layers.
I visualize the problem in attached curves. When processed normally, blue is much on the toe and thus lower in definition and contrast. Normal push processing won't help much in this situation, as it boosts also red contrast, driving the crossover problem even worse.
I find that a good thing to do is find a processing "fault" that normally causes crossover to another direction, and combine this with push processing. The error should be such that creates bluish cast in the whole image and especially in highlights in the final positive print.
But is it easy to make the top layer develop more than underlying layers, for instance, pH, temperature and time variations?
Perhaps this tech pub from Kodak could help. Look at the charts from page 29 onwards.
Last edited by Anon Ymous; 09-30-2010 at 06:33 PM. Click to view previous post history.
LD-Dmin would probably be the most interesting figure, giving shadow (toe) contrast (definition), not plotted there but plottable from the LD & Dmin plots.
It seems that increasing temperature boosts blue vs. red contrast as desired whereas increasing time does not, so it would be desirable to push process by increasing temperature, not time, in this situation.
Also, these charts give a good note that decreasing agitation lowers the contrast of blue most, so it won't be a desirable way to try to preserve reds from overexposing.
Mix error for part C -- that contains the CD-4 IIRC -- shows that overdosing it would be just what I'm after. HD-LD plot shows that green contrast stays constant, blue increases and red decreases, and Low Densities have a nice little contrast boost in blue compared to red and green.
I could be way off, but I believe I recall PE mentioning that iodine content helps keep the development between layers even. Perhaps adjusting that can give you different balance between colors.
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Well my conclusion is that in the future I'll develop C-41 films shot in tungsten light in a higher temperature, like 39 deg. C, as this could be a bit better for blue than increasing time, and this does not need any chemical modifications.
Sure enough.. I was hoping that perhaps you had tried it and were successful. It's an elegant solution to an annoying problem.
[del]Expose for filter factor (without filter)[/del] sorry read the need for speed part.. Try Rodinal 1+100 stand/semi stand for [del]an hour[/del] 2 hours, rinse, fix, rinse, bleach, rinse, C-41, rinse, bleach, rinse, fix, stab.
[del]Works well (for me)[/del] (test it first )
Below is not substantiated.... just what I found in docs...
I also found this in some E-6 first dev notes
"To decrease yellow: increasing thiocyanate 0.1 g produces a very noticeable change. To increase yellow: decrease thiocyanate 0.1 g."
Since yellow is the first layer (blue once inverted/printed).... I'm guessing you cant decrease a chemical not present
I also found in E-6 colour dev notes that lowering pH balance gives blue/magenta colour balance, raising it gives yellow/green balance. (edit: these were notes on CD-4 based E-6 colour dev... effect was different on CD-3 based, but this should work with C-41 then)
So higher pH = Yellow + "Green" (Cyan (Red on print, but from magenta?) + Yellow) on neg..... should help?
I just had a theoretical play with a tungsten shot digital raw (yes yes i know...), setting it back to daylight balance (typical tungsten cast) and pushing the magenta balance helps balance it. The other is pushing the blue balance Magenta seems to effect the red very slightly (daylight balance was 5500K, +10 magenta shift, obvious tungsten cast, correct balance was 2750K, +22 magenta shift).
I should also mention the pic was shot under consumer indoor tungsten lighting, which was a lower balance than neutral studio tungsten (3200K/0) lighting, and typically has a slight sickly green cast to it on a standard tungsten balance... however this sounds like your shooting environment anyhow
(how about some ceiling bounce flash?)
Last edited by Athiril; 10-19-2010 at 03:50 PM. Click to view previous post history.