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Dignan 2-bath color negative process, modification 1

Lachlan Young

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@koraks it stabilises/ preserves the CD-4 in an alkaline solution - and yes, I know that the formula tried to work around this. In some ways it's the least of the problems with this formula that seems to have little conception of how DIR couplers work to control highlight density.

Murray Kelly said:
PE always spoke ex cathedra but there were other opiniins, too.
Click to expand...

There are considerably more useful & usable ways to experiment with C-41 - this isn't one of them. That was essentially what PE was saying.

Unless you can find a way to modulate DIR release, you're going to keep going round in pointless circles.
 
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Alan Johnson

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Are these claims not merely an extension of the secretive, obscure and unpublished way in which the C-41 process was originated?
It is not the intention to produce yet another clone of Kodak's Flexicolor C-41 kit.
There is now a variety of films on the market that have a different color palette to Kodak's Colorplus.
Why not different colors from a developer?
 
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Murray Kelly

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So true Raghu. They colorise old film movies already. But .... you still have to make a print of the wedding dress that satisfies the mother of the bride.
 

Lachlan Young

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Alan Johnson said:
Are these claims not merely an extension of the secretive, obscure and unpublished way in which the C-41 process was originated?
Click to expand...

No. And it's not like Kodak (and everyone else's documentation) didn't contain a lot of information about how C-41 worked - and in particular DIR/DIAR couplers, which this formula (and all the silliness with B&W developers with XP2) fundamentally fail to understand in terms of exposure-emulsion-development interactions, preferring instead to dive onto a form of development that is largely less successful, even in B&W, than just using a conventional developer with a modicum of common sense.

Alan Johnson said:
Why not different colors from a developer?
Click to expand...

Z-131 contains many different ways to mess with your colour balance from regular C-41 - and you can do things with looping, bleach bypass etc, all of which don't completely misunderstand the emulsion-developer relationship like Dignan did.
 

Raghu Kuvempunagar

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Murray Kelly said:
So true Raghu. They colorise old film movies already. But .... you still have to make a print of the wedding dress that satisfies the mother of the bride.
Click to expand...

For fun I colourised the scan of a B&W slide using https://imagecolorizer.com/colorize.html. The result, though not faithful to the true colours, has the low-fi look that C41 developer tweakers seek. I'm sure the colourising technology will get better and better offering more control than what is possible using developer tweaking.
 

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Alan Johnson

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Unlike B/W development where there are plenty of relatively inexpensive books like The film developing cookbook, Photographic Processing Chemistry and Theory of the Photographic Process which explain how things evolved and how they work I am not aware of any books that similarly explain the C-41 process 1972 so quite often, and I may not be the only one, I don't understand what you are talking about.
Is there a good source of this information?

Here is Z-131:
 
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Raghu Kuvempunagar

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The Chemistry of Photography: From Classical to Digital Technologies​

By David Rogers

Alan, this book has some information on colour film that you might find useful. Lachlan might have better recommendations for reading on this subject.
 
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Alan Johnson

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The Chemistry of Photography From Classical to Digital Technologies : Free Download, Borrow, and Streaming : Internet Archive

The Chemistry of Photography From Classical to Digital Technologies
archive.org
From these 2 pages 110-111, it appears to me that with any alternative developer to C-41, on the final print or as otherwise viewed:

(1) It may be acceptable to increase the saturation of the blues and greens, like some landscape films & holiday snaps.
Preferably one should not start to increase while the other remains constant, at some level of exposure. I think this is called crossover.
(2) Flesh tones should look correct, like some portrait films.
(3) Neutral tones white/grey/black should stay neutral.

Will have to see if modified Dignan process gets anything along these lines.
 

Rudeofus

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There may be more reasons to go for two bath development than plain highlight compression: long developer shelf life, higher throughput per liter of developer, development of expired film of unknown pedigree. DIR couplers are excellent at controlling contrast, but not so much the others.

About the HAS: sulfite is know to react very slowly with oxidized PPD (and derivatives), that's why PPD+sulfite devs for B&W are slow and give poor contrast. There's a good chance, that sulfite scavenges oxygen as it enters the developer, but it will not scavenge oxidized PPD. Ron could never explain the reasons, and hinted that they were not even known ar KRL, but for some reason HAS protects PPD (and derivatives).
 

Raghu Kuvempunagar

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PPD-based B&W developers like MCM-100 and Edwal 12 have good shelf-life (easily six months and above if stored properly) despite not using Hydroxylamine. These developers have good amount of Sulphite unlike C41 developers. So I doubt the claim that Sulphite doesn't scavenge oxidised PPD (and derivatives) is true. More likely that C41 developers don't have sufficient amount of Sulphite needed for scavenging and this is by design.
 

koraks

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Rudeofus said:
There's a good chance, that sulfite scavenges oxygen as it enters the developer, but it will not scavenge oxidized PPD.
Click to expand...

Sulfite inhibits dye formation (I don't know through which process, I'm no chemist), which is why it cannot be used effectively as an antioxidant in C41, right? That means you need an oxygen scavenger that does not interfere with dye coupling; apparently HAS fits the bill.
 
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Alan Johnson

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Here are a landscape and a portrait on 10 yr expired Jessop SHR 100 =Agfa 100 in modified Dignan 2-bath@37C.
Since the scanner was left on auto I assume the negatives would also provide darkroom color prints [never done this].
They may be slightly unsaturated but is this not a popular look with movie film [no experience with this] ?

 

koraks

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Alan Johnson said:
Since the scanner was left on auto I assume the negatives would also provide darkroom color prints
Click to expand...

Ah, if only that were true...don't underestimate the magic your scanner is capable of!

Alan Johnson said:
They may be slightly unsaturated
Click to expand...

That's actually not such a bad thing here. With more saturation, the crossover might have become objectionable. Now it's just a nicely toned-down representation of a summer afternoon.
 
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Alan Johnson

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This shows the result of a quick color correction after developing in the modified Dignan process.
I don't know how close the C-41 process would come to the original printed chart.
 

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koraks

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Alan Johnson said:
I don't know how close the C-41 process would come to the original printed chart.
Click to expand...

Closer than this, that's for sure. Note the crossover if you look at the grey scale: the dark grey patches are blue, the light grey ones a kind of lime green/yellowish, suggesting crossover on the magenta/green axis as well as the blue/yellow one. All the color patches are quite far off the mark as well.
In my experience there will always be slight anomalies, even with well-processed C41, but nothing even close to this.

BTW: did you print (inkjet/laser) that test chart before photographing it? You do realize that you're introducing a massive problem by doing this? Film doesn't see what our eyes see! Think about how a printer blends colors and what film expects to see.
 
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Alan Johnson

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The chart is from here:

File:Color Checker.pdf - Wikipedia

en.wikipedia.org
I made an inkjet print of it [1] , photographed it on Ektar developed by the modified Dignan process and printed out a color corrected version of an auto scan [2]. Finally photographed [1] and [2] together with my phone. It gives a rough comparison.

Looks like I will have to rely on AA, "The negative is the score and the print is the performance", not trying to copy C-41.
 

koraks

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Alan Johnson said:
I made an inkjet print of it
Click to expand...

Yeah, so that's not a very reliable approach towards using a color checker card. In fact, it introduces so many problems right at the start that you'd be much better off photographing a couple of real world objects instead (perhaps a face, some fruit etc) and then compare your test film/prints with the real scene.
Or buy a properly made color checker.

If you want I could take a stab at explaining why inkjetting a color checker is fundamentally flawed for this purpose, but it'll have to wait until tomorrow (EU here).
 
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