Diluted C41 Tested

I haven't tried as drastic a 'push' approach as you describe above David, but a more limited attempt. Indeed it yielded quite good prints with seemingly accurate and saturated colors. Also distinctly more pronounced grain, which contributed to a sense of higher sharpness, although this would not necessarily fit every type of image. Nonetheless, I regarded it as a quite successful attempt.

koraks said:

I haven't tried as drastic a 'push' approach as you describe above David, but a more limited attempt. Indeed it yielded quite good prints with seemingly accurate and saturated colors. Also distinctly more pronounced grain, which contributed to a sense of higher sharpness, although this would not necessarily fit every type of image. Nonetheless, I regarded it as a quite successful attempt.

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We are searching for, and finding, permission to be devious with regard to the Yellow Father. It is not so difficult to quietly deny His Law and find out that there just might be something rewarding out there for all of our instigating efforts.

How much deviation has there been through the years with B&W!!! Then why not with color, also? We must tacitly anchor ourselves with the 'correct, theoretical way', in order to keep our bearings. But then we deviate, just for the fun of it, claiming artistic license as our bail bid to prevent being thrown into the jailhouse.

In other words, continue to exhibit a profound respect and understanding for the sagacious teachings of Ron Mowrey, but every once in a while sneak a peek at something a bit salacious and risque. - David Lyga

Fortunately nobody forbids us to experiment in this regard!

koraks said:

Fortunately nobody forbids us to experiment in this regard!

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Actually, you would be surprised with the number of those who shout 'sacrilege'. To many out there, doing what I say is anathema. I really mean that. But, so what! They mean well, and, to tell the truth, they are the anchor for these processes (like David Lyga is the anchor for correct English usage, to the annoyance of MANY).

This is the central reason why I hold Ron Mowrey so high. I KNEW that what I was saying about these processes was making him wince. But, like the thorough gentleman that he was, and with a level of intellect and forbearance so high, he not only tolerated me, but also found reason to think that there also was a place in this world for such a rebel. To me, this is indicative of profound character.

We do what we wish to do, as long as we are harming no one. Deviation can be a spice for life. - David Lyga

I re-read David's original thread and by the end my head was spinning so much it became difficult to continue to extract what if anything was agreed on. What was clear over a 3 year period was that there were those who felt it had merit and those for whom in varying degrees it has drawbacks. As far as I could see the two parties remained irreconcilable over that whole period but that is often the way on Photrio

What did strike me and it was something that not even the detractors mentioned was what appeared to be a fundamental shift in the order of the process. From what I gather the standard process is dev, stop, bleach and fix with appropriate water rinses but in David's process fix comes before a form of blix and there isn't a bleach stage per se at all. It wasn't clear to me if the fix was C41 fix or B&W fixer. As the whole process is done in a lightproof tank or so I assume the benefit of being able to switch the lights on after the fix stage seems redundant. Wouldn't the light go on once the tank is loaded anyway?

The tread then spent most of the next two years debating how much out of spec David's process might be and the danger or even the inevitability of colour crossover loomed large.

As far as I could see David submitted a few prints done under an enlarger and these looked fine but as far as I could see there were no other prints to be seen Clearly the more prints that look fine then the greater the evidence that colour crossover is at worst unusual and at best may be non existent if the prints are OK

So on that basis has anyone who said they'd try David's method in the first thread done so and David have you got more prints to show us which I assume will be straight scans of RA4 prints and this the "real deal"? The problem nowadays is that so much of what we see as prints are in fact scans of neg which are then reversed and that brings in scanner setting etc

So in summary I am looking for a discussion around my second paragraph including hopefully David himself and then evidence, if there is any, of others using David's method including prints that you David have also done.

One of the problems I believe we have here on Photrio is that for instance discussions start constructively on any "What has gone wrong here" threads about causes until the OP mentions that for instance he developed a film using a C41 process that did not require 100F then any attempt to find the cause which might be a lot of things suddenly stops or tends at the very least to get bogged down immediately with the breaking of a shibboleth held dear by those often make their voices heard more loudly than others. I use that as an example of what I see on Photrio a lot and NOT as something I am hoping to engage in a debate

Thanks

pentaxuser

pentaxuser said:

The problem nowadays is that so much of what we see as prints are in fact scans of neg which are then reversed and that brings in scanner setting etc

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The images in my first post are indeed negative scans, converted to positive en photoshop so all scans are exactly the same, If I use all the "restore colors" and "film profile" in vuescan this is what I get.

The colors in the diluted form doesn't bother me, but the grain is coarser (but could be the scanner, it does not have much resolution)

pentaxuser said:

What did strike me and it was something that not even the detractors mentioned was what appeared to be a fundamental shift in the order of the process. From what I gather the standard process is dev, stop, bleach and fix with appropriate water rinses but in David's process fix comes before a form of blix and there isn't a bleach stage per se at all. It wasn't clear to me if the fix was C41 fix or B&W fixer. As the whole process is done in a lightproof tank or so I assume the benefit of being able to switch the lights on after the fix stage seems redundant. Wouldn't the light go on once the tank is loaded anyway?

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There is some trickery involved with David Lyga's special C-41 process. Number 1 is, of course, the high dilution of C-41 color developer. The aspect which you just drew attention to is the specialized silver removal process.

Allow me to provide some theoretical background for this procedure: one of the special properties of C-41 film are these embedded DIR couplers. These couplers release a very powerful restrainer wherever development takes place. This keeps highlights well under control (---> the great latitude of C-41 film), and it creates Mackie lines near density steps, which give an impression of higher sharpness.

However, these DIR couplers come with a price: the restrainers released during development form very insoluble silver salts, which are very difficult to fix. Think Silver PMT with a pKsp ~ 16. If you go the regular route (bleach wash fix), you need a strong fixer to dissolve these very insoluble silver salts, and with plenty of capacity to take care of the large amount of Silver Bromide from both the undeveloped silver halide grains and the bleached silver. You need a fixer to cope with very difficult to fix silver salts and with a high silver load from at least three color layers. Such fixers either exhaust very quickly, or they need some expensive ingredients like Ammonium Thiocyanate or DTOD.

David Lyga solved this problem very economically by splitting the silver removal process into two parts: his first step uses a strong fixer to fully dissolve these poorly soluble silver salts and the undeveloped Silver Bromoiodide grains. His second silver removal step uses a dilute version of Farmer's reducer to remove all the remaining silver present as either metallic silver or as Silver Bromide.

There is one theoretical drawback of this approach: if you use thiosulfate to fix an emulsion which contains part silver part silver halide, some of the silver can be converted to Silver Sulfide. We all know the brown images we get, when we rehal bleach a black&white print, that's the Silver Sulfide formed during fixation. If you go through a bleach then fix sequence, this effect will not take place, but if you fix your film before bleaching the developed silver, there may remain some Silver Sulfide in the emulsion. It may cause some color deviations, but at least it's stable, so I wouldn't worry too much.

Rafael Saffirio said:

The colors in the diluted form doesn't bother me, but the grain is coarser (but could be the scanner, it does not have much resolution)

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Yes, the grain in the right scan looks quite a bit coarser, but is there a chance, that sharpness is also slightly higher? Both effects would be the expected results of developer dilution.

Rudeofus said:

. If you go through a bleach then fix sequence, this effect will not take place, but if you fix your film before bleaching the developed silver, there may remain some Silver Sulfide in the emulsion. It may cause some color deviations, but at least it's stable, so I wouldn't worry too much.

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Thanks for that explanation. In David's process can we be sure that the color deviations that may( but not definitely?) be formed are correctable when printing RA4. i.e. it is a simple correct to the Y and M settings compared to what a "normal process " C41 negative requires?

pentaxuser

Rudeofus said:

There is some trickery involved with David Lyga's special C-41 process. Number 1 is, of course, the high dilution of C-41 color developer. The aspect which you just drew attention to is the specialized silver removal process.

Allow me to provide some theoretical background for this procedure: one of the special properties of C-41 film are these embedded DIR couplers. These couplers release a very powerful restrainer wherever development takes place. This keeps highlights well under control (---> the great latitude of C-41 film), and it creates Mackie lines near density steps, which give an impression of higher sharpness.

However, these DIR couplers come with a price: the restrainers released during development form very insoluble silver salts, which are very difficult to fix. Think Silver PMT with a pKsp ~ 16. If you go the regular route (bleach wash fix), you need a strong fixer to dissolve these very insoluble silver salts, and with plenty of capacity to take care of the large amount of Silver Bromide from both the undeveloped silver halide grains and the bleached silver. You need a fixer to cope with very difficult to fix silver salts and with a high silver load from at least three color layers. Such fixers either exhaust very quickly, or they need some expensive ingredients like Ammonium Thiocyanate or DTOD.

David Lyga solved this problem very economically by splitting the silver removal process into two parts: his first step uses a strong fixer to fully dissolve these poorly soluble silver salts and the undeveloped Silver Bromoiodide grains. His second silver removal step uses a dilute version of Farmer's reducer to remove all the remaining silver present as either metallic silver or as Silver Bromide.

There is one theoretical drawback of this approach: if you use thiosulfate to fix an emulsion which contains part silver part silver halide, some of the silver can be converted to Silver Sulfide. We all know the brown images we get, when we rehal bleach a black&white print, that's the Silver Sulfide formed during fixation. If you go through a bleach then fix sequence, this effect will not take place, but if you fix your film before bleaching the developed silver, there may remain some Silver Sulfide in the emulsion. It may cause some color deviations, but at least it's stable, so I wouldn't worry too much.

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NOw I HAVE MY ANSWER AS TO WHY I "NEED" TO FIX FIRST, THEN BLIX. THANK YOU.

There are two reasons why I fix first: 1) It is just easier to clear the film. (C-41 film is very difficult to clear out the silver halides. I never knew why, but it just is.) and 2) there is an evil contamination that takes place, turning the film green, if there is so much as a molecule of developer in the film when it hits the potassium ferricyanide. To make absolutely certain I am not confronting that, I fix first. Somehow that really gets rid of the last vestiges of developer (my chemistry idiocy shows forth here) and that is how I accomplish this. I don't know 'why' but I know what works. That is going to be the extent of my 'intellect' that will be available to serve your needs.

OK, fact be known. I have NO scanner and my ONLY Internet source is an old Samsung Chromebook. "To scan", I take a picture with a VERY cheap digital camera. Color gets compromised according to the lighting. I know VERY little about digital technology. VERY LITTLE. In addition, my post was written four years ago. Within the past year I have almost completely stopped developing C-41 film and now concentrate solely on B&W. I CAN still process C-41, as I still have much chemistry, but I sold off MOST of my C-41 film within the past three months at a decent price. I still have some, but let us face facts here, my 'scans' are not going to be too great.

Another OK: I know that my lack of scans sounds like a David Lyga scam, but it is not. I am sincere here, but do not possess the amazing digital abilities that most of you seem to always have at the ready.. So, what to do....believe me? trust me? condemn me? question my intent? I know that none of you want to be so nefarious, but facts are facts. My 'darkroom' is within my living quarters. My living quarters? (Are you prepared for this?) They consist of: a 10 foot X 12 foot efficiency in Philadelphia. That efficiency includes a 'kitchen', a bathroom, a sleeping area, and ... a 'darkroom'. Your 'casual' ability to make immediate technological transfers between analog and digital is something which I do not possess, neither quantitatively nor intellectually. You are going to have to be satisfied with the tiny crumbs I disseminate. If that is not good enough, then please try elsewhere.

Personally, I think that the "one month old membership" of Rafael Saffirio is one of the best things ever to happen on either APUG or PHOTRIO. Whether or not you agree is, and remains, up to you. He seems to be the ideal conduit, bridging analog and digital technology.

In summation, what I am getting at is this: most of you have dedicated equipment which you readily take for granted and think everyone else possesses.. I do not have this. In fact, I have a Tracfone flip phone, not a smart phone. Maybe this is why I am always searching for ways to circumvent these severe restrictions and have, throughout life, made due with what I have. I do not have this stuff, materially or intellectually, that you so casually take for granted. Sorry, but I can not simply 'run off' some images which will satisfy your visual needs, which will immediately transport, to you, a definitive proof that forces you to accept my legitimacy. You are going to have to be satisfied with mere crumbs. - David Lyga

Rudeofus said:

very insoluble silver salts, which are very difficult to fix

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Before doing this I fixed a piece undeveloped color film in some ilford rapid fixer 1+4 and in cleared in one minute, is this test enough? Or could the film be clear and still have silver salts?

I understand your point David about your circumstances but presumably you developed quite a lot of C41 negatives, most of which you never turned into prints and it sounds as if you have no means of doing so now. I noted that the few prints you showed on the original thread were on a site of some kind. Is it not possible to link us to those pictures or were they not prints?

I am a little confused as to what your scope is to give us the evidence I mention as important.

It is early days yet but I haven't see anyone who spoke on the original thread about trying your method placing a picture on a thread or in the gallery to which they mention it as being the David Lyga method. I may be just more honest or more naive than most but if I have used your method and found that it worked well I'd want to give you full credit. So on balance I can only assume that few if any have tried your method despite saying they would

None of which, of course, is your problem or fault

pentaxuser

In #16 this is erroneous. It should be deleted, as the above formula already mixes per manufacturer. My error.

"Don't complain to me about not being able to measure 9.4 mL because I will tell you to mix as per manufacturer first, then dilute when you process film."

David Lyga said:

there is an evil contamination that takes place, turning the film green, if there is so much as a molecule of developer in the film when it hits the potassium ferricyanide.

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In some post that I can't find PE said something about the C41 developer reacting with the ferricyanide, maybe that is the green color as a result, to avoid that reaction I used the steps suggested here (by PE himself )

Regarding equipment: I do have many things needed for and hybrid workflow but everything is ancient, for 35 mm negatives I use a Nikon LS-1000 and for 120 an Agfa Duoscan, all that connected to a PowerMac G5, so top notch tech... 20 years ago!!

Back to the topic of C41 developer I did the test because I was curious and could not find some side by side comparison and for an economical reason, I live in Santiago (that is in Chile) here you simple can not find C41 developer locally (I'm sure that the few lab that remain have some kind of secret society because I could not find an importer of Kodak or fuji chemicals).
Not just here in photrio but in many US base forums some members say "just go and by some more developer or whatever" that is completely understable but for me and probably others that is not so easy, for example: the 1qt Arista C-41 liquid kit that I bought from freestyle was $25 + shipping, as is ORM-D it must by ground to Miami, where a forwarding service send it to Chile, then there are taxes, import fees and whatever but in the end that kit cost me $75 USD, and the 4 liters RA-4 that freestyle sells for $50 to my house was $145 USD. (of course the powder C41 version is cheaper, but it is nowhere to be found)

In conclusion I'm very interested in every way I could make the most of that developer.

Now that I know that the ferricyanide bleach works maybe the next time I'll buy some 5L flexicolor developer and starter.

Rafael Saffirio said:

View attachment 248230

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This is unrelated to the dilute developer experiment, but I'm a bit worried about the big difference between your blix and separate bleach and fix strips. I'm not sure where the problem is, but a possible hypothesis is that your blix isn't working properly and it's not removing all of the silver from the film. If you then scan the test strips/frames and adjust contrast and color balance for the blixed strip, it's plausible that a properly bleached and fixed frame will show reduced contrast and a different color balance compared to the improperly blixed strip. If all works well, a blixed and a bleach + fixed film should look nearly (or entirely) the same. This is not the case here, so you do have a problem somewhere that I'd suggest looking into.

Concerning the dilute developer experiment and the possibility of crossover: to test this, it's a good idea to photograph a scene with a greater contrast (higher scene brightness range or SBR). A photograph of a color checker chart will typically have very low contrast in the range of maybe 2-3 stops if you're lucky, which means that the resulting negative won't have true shadows or true highlights - the entire scene will be clumped together in a small part of the curve. If any crossover issues exist, you'll barely be able to see them this way. To solve this, you could either photograph a scene with a high SBR, or you could shoot your color checker card at different exposure levels, e.g. one at -2 stops, one at +/-0 stops and one at +4 stops. That would simulate a higher SBR as well (but you'll have to be careful to scan or print the frames with the exact same settings!)

Re: the issue of ferricyanide and color shift: it's indeed known that dichroic fog will be formed if ferricyanide follows the color developer and there is any amount of carryover of developer into the ferricyanide bath. Use a stop bath after development and preferably a wash step after the stop bath (or two washes, even better). This is to prevent acid stop bath to carry over into the ferricyanide, which can result in the formation of Prussian blue.

Concerning making the most of C41 developer: you could also try a replenishment regime. For minilab chemistry, replenishment rates are always provided in the datasheet of the developer. If none of those data are available for your manufacturer, you could depart from the data of another manufacturer and through systematic testing work out the correct rate for your chemistry. But that's a rather tedious process.

I tested this diluted developer sometime back, and using a densitometer measured and plotted the negative curves of a gray scale. None of the curves were straight on the linear portions but had slightly irregular shapes to them. The cyan curve was lower in contrast than the yellow and magenta curves, most noticeable in the higher densities. This is crossover. I believe Greg Davis had similar results using control strips. The mask color was also different than usual. The gray scale on the OP's third test (diluted) definitely shows a shift in color from light to dark (crossover) much more noticeable than the first two, and similar to the prints I made from my negatives. The second set of scans shown looks quite different from the first, so it only shows it is difficult to tell anything concrete from scans. The results I observed should not be surprising to anyone familiar with the critical nature of the C-41 process, as PE had discussed many times.

The crossover I measured in my negatives is not correctable in an RA-4 print but might be correctable in Photoshop if one is skilled, but is it all worth the trouble over just using the standard process to begin with? I only RA-4 print, and the crossover is not acceptable to me, so I stick to the standard development, producing easy to print negatives.

I am not trying to tell anyone not to try this process, only to warn them what they can expect based on experience. YMMV, so I urge users to do their own tests and make their own judgements.

I too, use a ferricyanide bleach (readily available and much more economical than standard bleach), following an acetic acid/sulfite stop/clearing bath, and a good wash, and do not measure or observe any problems over the conventional bleach. I use Kodak C-41 fixer.

koraks said:

I'm a bit worried about the big difference between your blix and separate bleach and fix strips.

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I'm curious about that difference also, a better test would be develop together then fix, cut the frames and then blix one, and bleach refix the other.

RPC said:

The results I observed should not be surprising to anyone familiar with the critical nature of the C-41 process, as PE had discussed many times.

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It may (or maybe not) surprise you, but I don't care about "perfect, densitometer and kodak approved negatives" if the colors look nice (skin tones are not green or something like that) it is enough for me.
I shoot film because is fun, and I like the real, physical aspect of is, been able to have the negs in my hand and seem trought the light. If I ever need or want "perfect" color, balance, saturation etc I simply take of my digital cameras shot RAW and be done with it, lets be real here film is good and nice but It is obsolete today if you want perfection go digital.

I did a quick test earlier today with some very old Superia 200 in Fuji minilab C41 diluted 1+9 developed for 10 minutes at 37.8C and then contact printed onto RA4 paper. I also did a test strip in regular C41 to compare. The results are fairly consistent with the ones you showed, with a few additional observations:
* Contrast is a fairly close match, but a tad on the low side. 10 minutes development at 1+9 dilution is certainly not too long in any case. I'd recommend 11-12 minutes if normal contrast is desired.
* Fog is higher with the 1+9 dilution. Not a big deal; it can be simply 'printed through'.
* Color balance for the 1+9 dilution shifts dramatically towards blue (in the positive/print). I could mostly correct for this through filtration, although I needed to go lower with yellow in my filter pack than I have ever had to do with any kind of film, no matter how experimental or messed up.
* There was some crossover, and while it was moderate, it didn't look very pretty to me. Highlights remain cold/blue with a hint of magenta while shadows go warm and tend towards green. In RA4 printing this can of course not be fixed.

I also noticed the developer oxidizes like crazy. When I mixed it, it was virtually colorless with the slightest hint of yellow. When it had warmed up to processing temperature, an hour or so later, it was a straw/yellow color. Of course not only the developing agents and activators are diluted, but also the antioxidant (hydroxylamine). Looks like it gets below a critical threshold in this dilution, which means that this dilution is definitely for immediate use after mixing and one shot only. This brings the question if it's really such an economical approach; it's quite likely that a replenished system will be more or less the same in terms of costs, but of course would operate within official specifications and allow the normal C41 development time.

All considered my conclusion is that it is not a perfect approach and the flaws seem pretty inescapable, but the results may still be acceptable for some photographers. It's definitely not a horror story from an amateur/hobbyist viewpoint. Most amateur photographers would likely qualify the color problems as minimal after correcting the huge yellow/blue shift. Those with a critical eye for color, however, better stick to the official process parameters, as this is definitely a compromise. Since C41 developer is still quite cheap around here if bought in somewhat larger volumes, and I've got quite a bit sitting around here still, I think I'm going to keep it at this for now with this route of experimentation. I was curious to see for myself if it works, and it does, of sorts. I can easily see why many people who try it would be enthusiastic if they have difficult access to a reliable supply of C41 developer.

First, 'normal' negative contrast does not apply to color. The hue differences make up the 'contrast'. The correct color negatives look 'low' in contrast, unlike with B&W.

Second, the straw color change I do not think was the result of oxidation within one hour. The colors of the developer solution change with the addition or water. I think that the straw color was the result of the chemistry 'settling'. I know that that explanation sounds terribly naive, but that is what experience tells me.

Whether there is an enhanced fog level with dilution is something that I am not really aware of but that supposition is interesting and I would like to know why.

I do wish to say this to Rafael who noted drop in resolution with dilution. This I vehemently deny. I have never noticed this and maybe there were other reasons in your experiment. - David Lyga

Rafael Saffirio said:

It may (or maybe not) surprise you, but I don't care about "perfect, densitometer and kodak approved negatives" if the colors look nice (skin tones are not green or something like that) it is enough for me.
I shoot film because is fun, and I like the real, physical aspect of is, been able to have the negs in my hand and seem trought the light. If I ever need or want "perfect" color, balance, saturation etc I simply take of my digital cameras shot RAW and be done with it, lets be real here film is good and nice but It is obsolete today if you want perfection go digital.

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RPC said:

I am not trying to tell anyone not to try this process, only to warn them what they can expect based on experience. YMMV, so I urge users to do their own tests and make their own judgements.

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Digital's perfection is highly debatable. Film, particularly medium and large format, has many advantages over digital but that's another thread in a different forum.

David Lyga said:

First, 'normal' negative contrast does not apply to color. The hue differences make up the 'contrast'. The correct color negatives look 'low' in contrast, unlike with B&W.

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My 10 minute 1+9 negatives exhibited less difference in optical density between highlights and shadows, lower gamma - call it whatever you want. Contrast, as far as I know, is a perfectly accurate term.

Second, the straw color change I do not think was the result of oxidation within one hour. The colors of the developer solution change with the addition or water. I think that the straw color was the result of the chemistry 'settling'. I know that that explanation sounds terribly naive, but that is what experience tells me.

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Immediately after mixing the 1+9 dilution the solution was nearly colorless. After an hour it was yellow. The regular working strength C41 developer from Fuji that I use is also straw yellow immediately after mixing and remains that color unless it oxidizes. When exposed to oxygen, the yellow color deepens and eventually the stuff turns brown. Obviously it's way beyond usable at that point. The yellowing I saw today in my testing definitely is oxidization.

I do wish to say this to Rafael who noted drop in resolution with dilution. This I vehemently deny. I have never noticed this and maybe there were other reasons in your experiment. - David Lyga

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I don't think he saw a drop in resolution, but an increase in apparent granularity. I did not test for this (at least not yet) as I only contact printed the strips so far.[/QUOTE]

Rafael Saffirio said:

Before doing this I fixed a piece undeveloped color film in some ilford rapid fixer 1+4 and in cleared in one minute, is this test enough? Or could the film be clear and still have silver salts?

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I have never tested the relationship between clearing of C-41 film and archival silver levels, however: I did notice, that patents showing very very active fixers (e.g. US6649331) use fixer times much higher than twice the clearing time. Clearing time of the fixer in US6649331 is 15-20 seconds max at room temperature, yet the patent prescribes 90 seconds at 38°C in a rapid access process.

I would therefore stick with 5 minutes fixation with anything resembling a standard rapid fixer, and going below that only with an extremely active fixer.

koraks, all I can say is that I have NO reason to doubt you but I also never had this problem. Of course, I usually dilute maybe at most, 20 or 30 minutes before use, but I do not have this problem.

I know that this is related only superficially, but it does bring about an analogy. Rodinal also turns brown after opening the bottle. Yet, it does not seem to affect its potency. So, all I can truthfully say at this point is this: in all my experiments, I never had troubles with oxidation after dilution. I don't know what to say about your situation. However, it does kind of pique my curiosity, in that maybe I had been standing on a precipice and almost fell off of the cliff. Thanks for giving this information. Yes, 1+9 is an extreme dilution, but workable if you do not cut corners. Maybe my temperature is really a degree or so higher than I think. - David Lyga

Well, the presence of some oxidation is not always a problem in itself of course, as the rodinal example illustrates. But with c41, a rapid rate of oxidation may make things a little unpredictable, that's all I'm saying. I also think it may contribute to the fog and perhaps the color shift as well. So a dilution of eg 1+4 may be a safer compromise, but I didn't test this.

So I went ahead and scanned the test that I did yesterday. Judging actual prints on a monitor is always tricky, so please bear that in mind when looking at these scans/comparisons. I tried to match as closely the prints I have in hand, but it'll never be perfect.

Again, I essentially did 2 strips of Superia 200 which I rated at 160 for this test and I exposed frames at -2 stops, 0 stops, +2 stops and +4 stops to emulate the dynamic range of a typical daylight scene. Lighting used was a single strobe with softbox positioned to minimize reflections off the checker; all ambient light was blocked. The exposure steps were done by changing the taking aperture, excluding variations in light temperature across the frames. The same equipment was used for both strips. The strips also came from the same individual 36 exp. roll.

The contact prints were made on glossy RA4 paper (no back markings, to be honest I don't know which paper this is...) developed in Fuji minilab chemistry in trays at room temperature (around 21C). Prints were scanned at the same time: both sheets on the scanner glass next to each other, so guaranteed to be scanned with identical settings. The black point was set a little below the curve to make the deepest shadows a little easier to compare. The white point was set a little to the right from the dmin of the print for an analogous reason.

Here's the overview. This is a composite of two contact sheets, so you're seeing 4 strips of film, but in reality it's just the 2 strips mentioned above, but contact printed twice, while adjusting the filtration settings for both prints to try and (sort of) match the colors.
The order of the frames, from left to right, is -2 stops, +4 stops, +2 stops, 0 stops, -2 stops.
The order of the strips, from top to bottom, is C41 regular processing, C41 1+9 dilution @ 10 minutes, and then the same thing again: C41 regular processing, C41 1+9 dilution @ 10 minutes.
I tried to match the bottom strip (so #4 counting from the top) to the top strip (#1). In doing so, I mostly looked at the 3rd and 4th frame, so the +2 and +0 stop frames, as they are the closest to what is likely to be the optimal part of the film's curve. To get the +4 frame decently in view, the contact prints were overexposed by about 2/3 of a stop. In reality, the +4 stop frames are somewhat closer to white than the digital scan suggests, but not all that much.


I also cut-and-paste a second comparison with the color corrected strips adjacently to facilitate comparison between the regular and 1+9 development:

• The massive yellow/blue shift is the first thing that becomes apparent. I printed this on my DIY led enlarger so I can put filter pack values here, but keep in mind they're not comparable in any way to typically encountered dichroic head filter cc's. The regular C41 processed strip was done at 120Y + 150M, while the 1+9 dilution at the bottom was printed at 32Y + 134M. On the magenta channel, 16 cc's may sound like a lot, but my led head is designed for substantially higher filter resolution, and those 16 cc's translate into something like 5 or 6 cc's for a typical Durst dichroic head. The difference between 120 and 32 on the Y channel is therefore also much smaller if you translate it to dichroic terms, but printing normal C41 negatives, I never need to go below 80Y with this head. This gives a bit of an impression how far out of normal bounds the 1+9 dilution negatives are.
• Notice the difference in density between the +4 frames in the color-corrected comparison, suggesting that the 10 minute development time for the 1+9 strip was on the low side.
• The top half of the first image also clearly shows the difference in fog between both strips. The 1+9 developed strip has significantly higher fog. This is also visible to the naked eye if the negatives are viewed on a light table. Due to the age of the film used (it's beyond its use-by date by about 15 years), it inherently gives substantial fog to begin with, which is exacerbated apparently by the long development time with the dilute developer.
• Looking more closely at the second image, you can see that the +2 and +0 stop frames between both strips come fairly close in terms of color rendition (notice in particular the background with the lighter grey squares on the darker grey fabric), although the match isn't perfect. I could have gotten either the +2 or the +0 steps matched better, but I would have had to make choices: optimize the large 18% grey patch, the underground, or any of the color squares? A perfect match between them was evidently impossible, emphasizing the differences in color rendition between both strips. Conclusion: you don't get the same colors from the film if you dilute 1+9, and no amount of filtering will entirely correct this.
• The pattern highlighted in the previous point becomes more apparent if you compare the +4 frames. Here, the color rendition of the 1+9 frame is much colder than the control strip, while at the +0 frame (second from the right, which is printed quite dark), the difference is not so great, although it depends on what spot in the negative you're looking at.
• Worth looking at in my experience is red, which always is the most challenging one to get right. Here, the control C41 patch at +0 stops shows a fairly OK tomato red, whereas the red patch in the 1+9 strip is a little more washed out. Earlier experiments I did with homebrew C41 chemistry also suggested to me that red is the tricky bit, as it just always seemed to do just a tiny bit better with 'official' chemistry.
• Now look at the frames of each strip from dark to light: the control C41 strip seems fairly linear, although not perfectly so, up to the +2 stop frame, but the +4 stop frame seems to shift into a more warm rendition across the board. This is in a large part due to the scanning as it's much less apparent in the physical print, where the +4 frame remains quite neutral. The bottom 1+9 developed strips does something different: this goes from a somewhat greenish rendering at the +0 stop frame (again, check the fabric underground on which the color chart sits) to a blue rendition in the +4 frame, although the big 18% grey patch seems to lean a bit more towards green than it does in the less exposed patches. Some other stuff happens as well; the cyan patch in the 1+9 version remains significantly darker than in the control strip, and so does the magenta patch. The red patch shifts to purple in the +4 frame, while it racks reasonably OK (with a little less saturation) with the control strip in the +0 frame. In the deep shadows, notice the big 18% grey patch, which is similar in color rendition within the C41 control strip looking at the +0 and -2 frames. Looking at the 1+9 strip the same patch goes from the fairly cold rendition I chose for this print to a distinct green rendition in the -2 frame. The overall suggestion is that neither strips track perfectly linearly across the density range in a single print, although the control C41 strip does quite OK up to the lightest frame and could be filtered for whatever exposure is chosen with a tendency at least on this paper for somewhat warm highlights, whereas the 1+9 strip shows some crossover from green shadows into blue highlights, suggesting more significant problems when printing contrasty scenes.

All considered, if you were to just process a roll in 1+9 and balance prints for it, I'd say they would come out reasonably OK if you're not too critical. However, if you compare directly to regularly processed film, there will be differences and it's likely that the prints from 1+9 processed film show deficiencies in color purity and exhibit crossover issues. As long as you're not deliberately looking for these, they may go unnoticed and the approach may be acceptable. If you're critical and try to get it just right, you may find that the 1+9 frames never quite seem to come out as you want no matter how you subtly change filtration. I'd rather not run that risk personally, as I know how it feels and how easy it is to waste a lot of time and end up with something that still remains kind of 'meh'.