Why is there color crossover in divided C-41?

Photo Engineer · Feb 22, 2013

Yeah, I see what you mean. I get ambiguous answers from my sources.

Do what works!

PE

AgX · Feb 22, 2013

Photo Engineer said:
The current ECN and ECP go through the same process.

If so, why does the industry still offer (list) both chemistries ranges?

Photo Engineer · Feb 23, 2013

It is because the information that I was given was apparently wrong and thus I was wrong. Either that or I misunderstood someone, or - sigh - I was just plain wrong.

Apologies to all!

My bad.

PE

Athiril · Feb 26, 2013

Okay round 2, modified formula different film.

Only change is the addition of 280mg/L of Sodium Thiocyanate (still think mine needs to be dried out a bit) to Bath A (Bath A and B were kept from previous go).

This time with fresh Kodak Gold 100 from B&H. One half was cut and run through a frontier C-41 to get as close to 'everyday C-41' as possible, other was the split bath (3m 15s A + 6ms B). 24 Colour Patch was shot on both at box speeds.

ColourChecker shots balanced with the 4th grey patch (4th darkest), and contrast matched as close as possible so any difference in the colour patches between the two will give more information on the colour.

Also going to use the Xrite software to create a profile for the C-41 and split-bath shots using the colour chart, so I can preview the difference between uncorrected and corrected colour, and see which colour patches shift the most (the 'most incorrect').

Scanning now, will edit and start including images after lunch break, I need to do a round about way of this.

Here are some initial results (will get some actual images to look at up later)
(I'm going to need to shoot a chart much closer up and redo this i think)
C-41 Gold @ 100

Split-Bath #2 Gold @ 100

Split-Bath #2 Gold @ 400

Athiril · Feb 27, 2013

Initial Observations between the C-41 vs CD-2 split bath test chart.. test chart colours are visibly more saturated from the split-bath when grey scale and contrast are otherwise equal.

Sorry for delays.. quick update.

All the charts when going through analysis were treated the same.. set white, black, and grey points, so that their relative differences minus balance can be seen.

The Gold 100 in #2 shot @ 800 indoors (haven't provided the measurements for this one yet)

1600 (different colour balance to above by the looks, just picking off the grey scale) - this is the point where skin tones get a larger error (colour points 1 and 2)

Images for the Charts in the previous post (I didn't try fiddling/matching these, just picking grey off the colour chart)

C-41 100

Split Bath #2 100

Split Bath #2 400

Athiril · Feb 27, 2013

Max 10 images reached above

Here is a scene from either

C-41, Gold 100 @ 100

Split-Bath #2, Gold 100 @ 100

If you tried to print them with the same exposure and balance, you might get something like this (top C-41)

There are a couple of issues with the chart analysis.. the large amount of grain.. and the charts need to be pre-balanced, so the accuracy of the pre-balance putting it however close to the ideal input chart etc (though they're all done in the same method). So that puts the absolute measuremed error accuracy into question, but at least shows relative differences.

Photo Engineer · Feb 28, 2013

One is tungsten and the other is daylight?

Looks like the cars are paring on the wrong side of the street.

PE

Athiril · Feb 28, 2013

Photo Engineer said:
One is tungsten and the other is daylight?

Looks like the cars are paring on the wrong side of the street.

PE

Images were taken in Australia

The bottom one is the +2 'push' 400 chart (which i thought was the best out of the split bath charts) which should be shown somewhere above.

Except in that case I used the same colour balancing settings as for the gold 100, showing it would have yo be printed significantly differently in the dark room then you would normally print C-41 film. Different filtration and exposure.

If you are able to balance the grey scale then theoretically it should print well. Key word is if. I should shoot a grey patch up and down and plot curves of this process vs C-41 process of the same film.

But the next roll I want to try is Superia 800 at night and see what extreme it is useful at.

It may very well simply be outside the range of filtration available to be able to make a neutral balance print in the dark room even though technically the colour is serviceable when the grey scale is neutral, as the print material isn't matched to it.

Unless one wants to fiddle with a print developer (perhaps a CD-3 split bath for the ultimate in laziness? ) but that's a can of worms I don't wish to open.

Or perhaps a blue enlarging light or 80A in the filtration path to give you more control of blue/yellow.

chuck94022 · Feb 28, 2013

Ok, this is all very cool. I don't understand it all, but it does seem that a divided C-41, while not perfect, is interesting.

Allow me to ask the related question of divided developers: does the formula here result in working solution longevity similar to Diafine? Because it is divided, does it last "forever"?

Photo Engineer · Feb 28, 2013

Dan, very fine results and yes, I did know you were in AU. It was late at night here as you can see, and I wanted to kid you rather than post a long answer.

I think that you have the problems ironed out. Just watch for the contrast difference. ECN is about 0.5 and regular C41 films run from 0.6 (pro films) to 0.75 (consumer films), and thus the color print materials and scanners are fooled by thinking that all negative films are C41.

As for divided developer keeping, that remains to be seen. CDs oxidize more rapidly and are trickier to stabilize. You can make a B&W concentrate that lasts years, but CD kits are known to go bad rather quickly, even as a 3 part kit.

PE

Athiril · Feb 28, 2013

Not looking to replace C-41 with any of this, ideally what I want is two things from two different formulations:

1) A large speed losing contrast increasing developer (would like the same amount of stops of range on the neg in a straight line but a steeper line.. ie reaching a higher dMax on the straight line), to only develop the fine grains and perhaps provide a solvent effect .

2) The extreme other end. As useful as possible for underexposed images.

Photo Engineer said:
Dan, very fine results and yes, I did know you were in AU. It was late at night here as you can see, and I wanted to kid you rather than post a long answer.

I think that you have the problems ironed out. Just watch for the contrast difference. ECN is about 0.5 and regular C41 films run from 0.6 (pro films) to 0.75 (consumer films), and thus the color print materials and scanners are fooled by thinking that all negative films are C41.

As for divided developer keeping, that remains to be seen. CDs oxidize more rapidly and are trickier to stabilize. You can make a B&W concentrate that lasts years, but CD kits are known to go bad rather quickly, even as a 3 part kit.

PE

Ignore the 'ideal' results, and think of the C-41 measured results as the ideal results, and compare those with the split-bath measured results, that shows hue shifting from the C-41 results.

I will see what the gamma for the red, green and blue parts are to balance the grey scale vs the C-41 charts.. that should also be telling. If the gamma/contrast of one part (say green image) is significantly lower than the others for example, you may have prints with either green shadow cast or magenta highlight cast depending on printing.

chuck94022 said:
Ok, this is all very cool. I don't understand it all, but it does seem that a divided C-41, while not perfect, is interesting.

Allow me to ask the related question of divided developers: does the formula here result in working solution longevity similar to Diafine? Because it is divided, does it last "forever"?

It does not last 'forever', last time I tried it a while ago, I found it stopped working after 6+ months, I don't know exactly when as I didn't use it very often (only a couple of rolls). I also mixed it up with tap water and no chelating agent.

The other issue is iodide and bromide build up (in both bathes) and weakening of bath A from some development occurring, and dissolved silver build up from my addition of thiocyanate.

Which may change developer characteristics with usage, my recommendation would be to replenish an arbitrary amount - it should theoretically self-balance to an equilibrium point.

The preferred Bath A I would like to use, is with CD-4 with enough alkali to neutralise the H2SO4, and then HAS to set the desired pH, maybe with a weak alkali buffer to get an extra amount of HAS for better keeping properties.

It is still quite economical, regardless of that, Flexicolor is also very economical, the cost is generally all in the bleach. One can be very economical in C-41 one-shot if they keep and replenish the bleach (and fixer too I suppose).

chuck94022 · Feb 28, 2013

This became such an interesting thread to me, with a ton of useful information on what seems to be an accessible, useful alternative to standard C-41 processing for the tinkerer. Not perfect, but certainly usable. The benefits of brewing your own, plus more time/temperature tolerance, balanced against some potential color shift and possibly grain/speed changes, seem to make it something quite interesting to play with.

Thanks Athiril (Dan) and PE for your contributions. Should this become a sticky thread?

Photo Engineer · Feb 28, 2013

Dan, quite frankly what bothers me is that the neutrals look good but the color balance is way shifted in the green example. So, they make good prints but with a different filter pack. Something odd is going on here.

I have looked at and re-looked at those images. Oh, nothing suggests itself to me except that the images are exceptionally high in contrast compared to the original chart. Many steps missing in the neutral scale.

Still thinking this out.

PE

Athiril · Feb 28, 2013

I'll get my hands on some paper to try optically printing them and comparing at some point.

Photo Engineer · Feb 28, 2013

My early trials along "odd" lines of processing gave the same cyan results as yours did but with crossover consisting of low cyan dye contrast and high yellow dye contrast.

Still Thinking this out.

PE

Athiril · Mar 1, 2013

This may help:

C-41 dye histogram (Gold 100 chart image), towards the right is increasing density (these are for the raw data, so the absolute values)

Split-Bath (pic of Gold 100 @ 400 chart image)

The yellow dye density range (dmax-dmin) is a little smaller in the split-bath image, magenta close to identical in dmax-dmin.

The cyan dye dmax-dmin is smaller in the split-bath image, by the same amount.

The magenta and cyan 'shapes' are a close match, the yellow 'shapes' the most different among the 3 but still bear some resemblance.

Photo Engineer · Mar 1, 2013

Dan;

Something looks wrong with the hue of the dyes. Is that real?

PE

Athiril · Mar 1, 2013

Photo Engineer said:
Dan;

Something looks wrong with the hue of the dyes. Is that real?

PE

These are just charts.. the hue is irrelevant, its just arbitrary values I chose to represent the cmy data, just so you can tell which is which. I just happened to colour them slightly differently

Photo Engineer · Mar 1, 2013

Well Dan, hue can vary due to the mask. If something goes awry, then the dye hues and mask color go off center.

I'm still puzzled by some of that. I wish we could talk.

PE

Athiril · Mar 2, 2013

The hues in the two charts are just colours I picked to colour them with, I did it by hand rather than numerically.

They are not related to hue on the film other than to say "this part is representative of yellow dye density range".

horizontal part is density, increases to the right.

vertical part how much of that image in the related dye is that particular density.

Photo Engineer · Mar 2, 2013

I was kind of referring to the previous CIE charts you posted and relating them to the histograms Dan. Something looks off to me but I cannot tell what. Perhaps it is your method of plotting. IDK for sure.

But, whatever is going on, I get cyan results when I try "odd" things with C41 films.

PE

Athiril · Mar 4, 2013

The method isn't perfect, but it should be consistent in between each test, so that relative shifts can be seen.

For the next test, it's back to Gold 100.

I've created a 3 patch chart on Lustre RA-4 paper which reads as follows (V, R, G, B) on a densitometer,

1.02 | 1.05, 1.06, 1.06
0.72 | 0.74, 0.75, 0.74
0.44 | 0.43, 0.47, 0.43

the goal was to create 3-stop chart of 9%, 18% and 36%.

I exposed up and down 3 stops apart each exposure, had to move indoors for the lower exposure values as I maxed out the aperture and shutter speed values on the poor AE-1.

Split bath roll should be -12 to +12 stops, C-41 should be -12 to +9 (hit last frame, as I made a few errors).

Results will of course have some margin of exposure error.

I think I should do this again with single frame patches to make it easier.

Kodak Gold 100 appears to give an additional four stops of developable shadow detail in the split-bath. (density differentiation in all three, R, G, B portions).

Both hit red as the limiting density limit in highlight differentiation (less than 0.01d measurable difference) before being limited by G or B.

I think there's a few more stops in the highlights as well before it breaks down, but I need to do another test to rule out error.

Why is there color crossover in divided C-41?

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