Color cast problem with DIY color negative chemistry

[originalwinslow]

From what I've gathered over the years, EDTA bleaches work but tend to be very slow compared to DTPA. A small excess of EDTA might fix that issue, I may try it sometime.

Ferricyanide bleaches work very well, but you MUST buffer them to avoid pH related issues with red stains, something that destroyed a large amount of film for me 30+ years ago. Half a gram of borax per 500 mL of ferricyanide bleach works wonders, I use it for C41, ECN-2, and E6. Only real drawback to it is that strong acids contaminating it WILL release hydrogen cyanide, and incomplete washiing WILL precipitate Prussian Blue (ferrocyanide) in both film and fixer.

Greetings all.

I have recently started my homebrew journey and began mixing my own Ferricyanide bleach in the Kodak "alternative bleach" mix of 40g Potassium Ferricyanide to 25g Sodium Bromide and fixing with Formulary TF-5 fixer. Developing ECN-2 with this combination gives me no issues. However, my first c-41 dev left SOME frames with mild stains visible in the low-exposure parts of the negative that showed as green upon scanning. I forged ahead and developed a second batch 4 days later which unfortunately sustained much worse red/purple stains clearly visible on the negatives. The green in the positive conversions was more present, but again mostly visible in underexposed portions of the negative. I re-bleached and fixed but no perceptible change on the negative was visible. I am working to find the root cause of this staining, which may have been from incomplete washing or an insufficiently acidic stop bath. I should note that I ran 20+ rolls through 2L of these bleach and fix mixes and the images seem to fully clear.

RPC as well as the "photo techniques" document recommend 80g Potassium Ferricyanide to 20g Potassium Bromide for c-41 Ferricyanide bleach. The "photo techniques" document states that the pH of this stronger mix should be 5.7 aka more acidic than the 6.5 for the 40/25 ECN-2 ferri bleach that I used. RPC notes a bleach time of 2.5 minutes, probably due to this lower pH creating a stronger bleach. He also says he dumps this bleach after 2 uses which seems wasteful as my "weaker" mix was apparently able to fully clear 20+ rolls (albeit with 2L of working solution). FPP uses ferri bleach in their kits and rates it for 20 rolls.

Considering these factors; what caused this stain? Reaction of the bleach with trace amounts of developer creating hydrogen cyanide? Reaction of the fixer to trace amounts of bleach creating prussian blue? I have been rinsing 3-4 times between each step. Vinegar stop bath (125ml 5% to 875 water) too weak? I did see more than usual blue in the water after washing out the stop bath. It seemed reminiscent of prussian blue but can find no visual aides that describe what it would look like on negatives and in any case that would occur after contact with the bleach/fix. It also looked to me like the deep blue created when pure CD-4 mixes with water...but that doesn't make sense either.

I suppose my first step is to mix all new chems and rinse more thoroughly and see if the problem persists. Psfred threw another wrench into this by mentioning pH of bleach can cause staining as well. I could buffer with borax to extend the lifespan, but what is my ideal pH range for the bleach? 6.5 +- .5 for the 40/25 mix and 5.7 +-.5 for the 80/20 mix? My 2L 40/25 solution had dropped to 5.8 after 20+ rolls....but I got staining from the jump so I dont think that was the cause. How much of pH deviation would cause staining? Again, I used this exact same process for ECN-2 with no issues.

Sorry for the long post. Any assistance is appreciated. I live in Puerto Rico and need to find a way to transition away from using 1L powder kits that are cost ineffecitve and often out of stock. Liquid chems will not ship here. I plan on mixing up some blix as per the OP as soon as I can source the EDTA/PDTA.

 

[koraks]

Welcome aboard @originalwinslow ! I've split off your post into a new thread; it seems to be warranted.

A few remarks.

I should note that I ran 20+ rolls through 2L of these bleach and fix mixes and the images seem to fully clear.

Could you please post some good photos of the actual negatives? Not scans, but photos that show the film as seen by the naked eye. Both backlit and in reflected light, please. I have doubts that your negatives have cleared effectively. 20 rolls / liter of fixer is on the high side. I suspect your fixer may be dead, or close to dead. Insufficient fixing on CN negatives tends to give color anomalies on the magenta/green axis. Although it has to be said that the example you've included seems so extreme that it's hard to believe this is associated with fixing. Hence thge request to see the actual film.

RPC notes a bleach time of 2.5 minutes, probably due to this lower pH creating a stronger bleach.

No, the ferricyanide bleach is just inherently quite aggressive. The small pH difference is not really a factor.
Have you replenished the bleach by adding bromide? I don't expect it's exhausted btw. Note that it's mostly (firstly) the bromide that gets used up, which tends to slow down the bleach.

Have you already tried re-bleaching and re-fixing an affected strip in fresh bleach and fix? It only takes a small amount of both baths to re-process a section of film. You can do this at room temperature; 10 minutes for both baths will be such a massive margin that complete bleaching and fixing should be expected. If you keep one half of the film strip out of the processing solutions, you can easily spot any difference that re-bleach/re-fixing may yield.

Considering these factors; what caused this stain? Reaction of the bleach with trace amounts of developer creating hydrogen cyanide? Reaction of the fixer to trace amounts of bleach creating prussian blue?

I see nothing here that suggests any Rrussian blue is being formed. The only place I'd see it happening in the first place would be between stop & bleach, and as long as you rinse the film in-between, it shouldn't be a problem. Again, this doesn't look like an accidental cyanotype problem to me.

I did see more than usual blue in the water after washing out the stop bath. It seemed reminiscent of prussian blue

How could that be formed? After the developer and stop bath, there's no ferricyanide in there to begin with. So that's not it.

It also looked to me like the deep blue created when pure CD-4 mixes with water

That's odd. CD4 in water yields a colorless solution that turns magenta (pink) as the CD4 oxidizes. Here's an example I just cooked up for you:

I never see blue in the wash water of fresh CN film. It's mostly magenta, due to the combined effects of oxidized CD4 and technical dyes embedded in the film emulsion that wash out slowly. This is true for Kodak as well as Fuji CN film. Harman Phoenix imparts a characteristic violently yellow coloration wash water/developer. Old Kodak films (20+ years) would impart an interesting, very deep cyan/red dye that acted as a sort of dichroic filter - it looked cyan/green under reflected light and red if you shone light through it. This is long ago.
I can't recall having seen any blue, though.

I could buffer with borax to extend the lifespan, but what is my ideal pH range for the bleach? 6.5 +- .5 for the 40/25 mix and 5.7 +-.5 for the 80/20 mix?

I've used ferricyanide bleach for quite some time for ECN2 film. I never buffered it, adjusted pH or anything - just ferricyanide + potassium bromide. Worked fine and it lasted forever. This is basically a bulletproof bleach and anything you might want to throw at it only risks at making matters worse.

TL;DR re-fix a strip with fresh bleach + fixer. Forget about pH adjustment on the bleach. See if that makes a difference.
In regular processing, rinse well after stop and before bleach. Preferably wash well after bleach. Don't overuse your fixer and keep in mind that the fixer will gradually die as ferricyanide bleach carries over into it.
Given on what I've seen/heard so far, my money is on a problem with your fixer. It's often difficult to identify partially fixed CN film. You need to hold it against the light just right, looking at the emulsion side; you'll see a metallic, slightly iridescent sheen to it. It'll be worse in some places.

 

[lamerko]

I have abused ferricyanide bleach quite a bit - its capacity is really high, as long as there is bromide available. As for the danger of hydrogen cyanide release, it is very small. Probably insignificant, unless you decide to pour concentrated mineral acid into the bleach. According to the official Kodak instructions, buffering this bleach is done by adding 1-2 grams of borax and note - lowering the pH by adding 2.5N sulfuric acid. Of course, I would not recommend it, but this concentration is much more than you can contaminate with the developer.
You can try to exclude some factors - for example, try everything as you are doing now, but replace the ferricyanide bleach with PDTA C-41 from some kit, just for a test. That way you will know for sure if it is from the bleach.
When working with ferricyanide, it is a good idea to clean it well before and after with a cleaning bath of 20 grams of sodium sulfite.

 

[originalwinslow]

Great, this feedback is very helpful in nailing down a consistent ferri bleach workflow.

Do you use/recommend the 40/25 or 80/20 mixture for c-41? Mixing at 40/25 costs me about $2.50/liter which is where I'd like it to be but if doubling the ferricyanide is absolutely necessary for full clearing or renders a more reliable solution for c-41 then I will bite that bullet. "Forever" sounds great, if I can get 30+ per liter I'll be satisfied. I have pushed PDTA blix from powder kits to 60+ rolls with only minimal color casts at the end of its lifespan but that might've been a bit reckless. However, I understand that separate bleach and fix are more stable...perhaps 60 rolls on a liter of ferri bleach isn't too crazy? At what pH deviation do you recommend introducing borax? I have read that the sodium sulfite clearing bath can reduce staining and that it can be mixed with the stop bath. Clearing bath of 20g to 1L of water after bleach to maintain fixer potency?

As for the fix; I used TF-5 for 3.5 minutes as the instructions recommend no more than 4 minutes for film. The fixer was freshly mixed when the first rolls came out with the green stain. Albeit the stain was much less pronounced than in my next development round four days later. This led me to conclude that weakened fixer was probably not the issue, yet it was also my first time using TF-5 so it's an untested variable. I used the same fix (but fresh 40/25 bleach) for a test roll developed in my first homebrewed c-41 developer (it worked great!) as well as for a few rolls of ECN-2. Same fix time etc and no stains whatsoever. TF-5 claims to be usable for 20+ rolls per liter and I was using two liters of solution which should be good for 40 rolls? That makes me think that it can't be a fixer depletion issue. I also do not see any reflective silver on the surface of the negative. I did test the pH of the fixer after the 20+ rolls and it was 8. I think TF-5 should be neutral at 7 but I have also read that pH doesn't particularly affect fixer strength. I will re-bleach and fix with fresh solution and check results. The stain also seemed more prominent on Kodak films vs Fuji. In fact, the Fuji rolls had no trace of staining. Could be coincidental.

The blue after the stop bath is strange and seems most culprit. I poured back my developer, immediately introduced the stop bath mix I mentioned, agitated for 10 seconds for a total of 30 second bath, discarded and rinsed 3-4 times. The dumped stop bath was not blue but the first rinse after the stop was very blue and gradually tapered off til the water ran clear. I had not experienced this quantity or strength of blue in the past. Could there be an issue with developer contamination? I was (and have always used) the cinestill (unicolor repackaged?) powdered developer due to import restrictions here in PR. I have ordered more to test as a control against my own homebrew developer. I can also test with the "depleted" fixer vs freshly mixed. All my chemicals EXCEPT stop bath are mixed with distilled water.

The other day I washed a speck of CD-4 off of a tool and it instantly turned the water blue. Perhaps it was an anomaly, my experience with these chemicals is limited. Weird.

Here is a backlit image of the film. Notice the stain varies in width and is concentrated always in the middle of the negative, but does not have consistent shape/tapers off. I tried to upload a reflective image but the site says the image size is too big (it's 366kb)

 

[Truzi]

This reminds me of an old thread, and while I had a link, it was the APUG days and I had to search for it.

The thread is about potassium dichromate bleach for color film, and Photo Engineer commented that when using alternate bleaches - including ferricyanide - with C-41, that a sodium sulfite bath is needed to prevent problems. It might be worth a read.

Potassium Dichromate Bleach?

On one of my trips scouring the net I came across this reciple for b&w slide processing (Dead Link Removed) which lists a bleach recipe: water 1000.0 milliliters potassium dichromate 10.0 grams sulfuric acid 12.0 milliliters Can someone shed some light on this, if this bleach...

www.photrio.com

lamerko said the same thing a few posts up.

 

[koraks]

Do you use/recommend the 40/25 or 80/20 mixture for c-41?

Doesn't really matter; just make sure the bleach time is sufficient to get the job done. Err to the long side; you can't over-bleach the film anyway.
I don't consider the ferricyanide bleach ideal to begin with, so I'd suggest moving away from it as soon as you can.

I have pushed PDTA blix from powder kits to 60+ rolls with only minimal color casts at the end of its lifespan but that might've been a bit reckless.

Quite reckless indeed; if you're getting color casts (any, at all) due to overuse of a blix, you're waaaaay out beyond the point where the blix was functional.

At what pH deviation do you recommend introducing borax?

As said, you don't need any pH adjustment on this bleach. Just potassium ferricyanide and potassium bromide, nothing else. It's pretty stable. If the bleach starts to turn green, it's apparently getting too acidic. Just discard it and mix up some new; it's not very expensive. I've not had this happen despite having run countless rolls through the same ferricyanide bleach, so there's no reason to believe this would be a practical problem.

I have read that the sodium sulfite clearing bath can reduce staining and that it can be mixed with the stop bath.

Yes, that's a good idea. I've never found it necessary myself; when I used a ferricyanide bleach, I also used the sulfuric acid stop bath recommended for ECN2 processing and I used to do a single rinse after that and before the bleach. That was sufficient.

Albeit the stain was much less pronounced than in my next development round four days later. This led me to conclude that weakened fixer was probably not the issue

So you used fresh fixer and got stain, then used the same fixer again and got more stain and then concluded the fixer couldn't be part of the problem...? I don't follow that line of reasoning to be honest.
I'm not saying that this proves the problem is associated with the fixer, but neither does it eliminate it as a factor.

The stain also seemed more prominent on Kodak films vs Fuji. In fact, the Fuji rolls had no trace of staining. Could be coincidental.

Could be. What films did you use, specifically?

The blue after the stop bath is strange and seems most culprit. I poured back my developer, immediately introduced the stop bath mix I mentioned, agitated for 10 seconds for a total of 30 second bath, discarded and rinsed 3-4 times. The dumped stop bath was not blue but the first rinse after the stop was very blue and gradually tapered off til the water ran clear.

In this process, I don't see a plausible cause of any blue coloration of the wash water after the stop bath. Your ca. 2.75% acetic acid stop bath is not too weak; I assume you use it one shot and then discard. If you do so, you can mix it down to 1% and still get good performance in my experience.
Are you sure you're seeing a blue coloration? I asked because it seemed earlier that we may have a misunderstanding between us on how we refer to hues.

The other day I washed a speck of CD-4 off of a tool and it instantly turned the water blue.

I can't explain that. I've worked with CD4 and CD3 a lot. The color as it oxidizes in water is as I've shown above.

Here is a backlit image of the film.

Yes, that shows (apart from unrelated underexposure on a few frames) a very strong magenta fog. I can see how magenta dye formation might result from developer reacting with the ferricyanide bleach, but the intermediate steps (stop + rinse) as you described them should prevent this.

There are a lot of unknowns in your process due to the use of non-standard chemistry. I'd start with a known-good process based on factory-made chemistry (i.e. a commercial kit of good quality), and then start swapping out components one by one in a systematic test. Sorry, I can't be more specific; there's too much going on here that can be a problem.

 

[lamerko]

What formula do you actually use to mix your developer?

 

[originalwinslow]

Thanks for the thoughtful responses koraks, I realize I introduced quite a few variables all at once and am now reaping my reward. Both the cinestill and FPP c-41 powder kits are out of stock and therefore I was pushed into prematurely making the leap to relatively untested processes in order to meet my client's deadlines. Tetenal press kit only ships within continental USA (and more than double the price at $65/blix-based) and Flic Film uses ferri bleach. I'm left with minimal options.

I assumed the fix was not the cause because it fully cleared my ECN-2 dev batches even after the 20+rolls (2L of solution). If we assume TF-5 is able to fully clear c-41 CN films (as PE claimed) then why would it leave a stain as a freshly mixed, unexhausted solution? Perhaps my agitation was insufficient? If insufficient fixing is indeed the culprit than a fresh fix round should clear the film. If not, the problem occurred elsewhere. Correct me if I'm wrong. Perhaps ECN-2 films clear more easily? I also do not see any sign of prussian blue in the fix. Is there another fixer you recommend? My research indicated TF-5 was an excellent option for "alternative" fixer.

I would like to move away from the ferri bleach but sourcing the ammonium ferric EDTA solution is an obstacle. I have the CAS number, only need a supplier that will sell me non-industrial quantities.

Specifically, the films stained were all Ultramax I believe. Mightve been a Gold in there as well.

Sorry, the mention of blue associated with CD-4 was erroneous. I just tested and you are correct, magenta when mixed with water. However I am certain of the blue hue after the stop bath. I will be ready to take a photo in my next dev session if it occurrs again.

Lamerko; I used RPC's updated formula found here https://www.photrio.com/forum/threads/diy-mixing-color-chemicals.190287/ but note that when these issues occurred I was using cinestill developer NOT the homebrew. Homebrew developed with no staining issues using FRESH ferri bleach and SAME (exhausted?) fix, adding yet another wrinkle to this investigation.

RPC's recipe worked well, but I am planning on adding the diethylenetriamine-pentaacetic acid pentasodium salt solution - 40% on future iterations to get it fully to PE's spec and extend the shelf life. If you have any tips...I am still in very early days. Many more tests are needed. I will include some images. They are Vision 3 500T cross processed c-41 so not perfect for testing but I've cross processed about 100 rolls of vision 3 in c-41 so I am familiar with the varied results. I have 400ft rolls, so slicing off 10-frames for tests is easy. I also ran a friend's cheap Fuji c-41 roll through the same soup and got good results in the few frames he managed to expose correctly so I am feeling confident at this point.

I just need to nail down the source of the aforementioned stain. If I wash 2x with 20g sodium sulfite and STILL get a stain then there must be an issue with the fixer...I think that's where we're at.

 

[koraks]

Thanks for diligently checking everything @originalwinslow - good work!

The blue color you report is meaningful; I suspect it may have something to do with the problem. I think it's either that, or something with the fixer. But the fact that you're getting blue coloration in the wash water is odd. I've not recently shot any Gold or Ultramax, but I'd be surprised if they are very different from other recent Kodak films in this regard.

Is there any opportunity in your process for ferricyanide bleach to carry over into either the developer or the stop bath?
Do you do a pre-wash before development?

I agree that TF5 should in principle be just fine. I don't agree with what you heard about the fixing time needing to be limited to a certain number of minutes; you can safely fixer for much longer than that.

Did the tests of re-fixing the affected film yield anything at all? Was there any change, whatsoever?

The 500T shots are too strongly compressed to make much sense of them. The 'La Brega' shot does show a color anomaly at the top of the frame. I think I also see a cyan stain in the sky on the hospital shot. The color on the shaded part of the lid of the cooler also doesn't look quite right. The BBQ has magenta tones where I wouldn't expect them. None of this necessarily points at chemistry/processing problems; they can in part be compression artefacts (set JPG quality to at least 90 to prevent this) and/or color balancing problems happening after/during scanning. This is why I generally prefer to look at raw negative scans; they take some of these problems out of the equation.

 

[originalwinslow]

Here are the same files with less compression. Also included raw negative scans. I did notice the light cyan stain in the hospital shot which I have not seen before when cross processing vision 3 in c-41 chems. Color anomalies similar to what you see at the edge of the frame in the "la brega" do happen sometimes when cross processing, I am not sure why, although here it does seem more pronounced. Could related to a mild light leak in my reusable 35mm canisters. In the raw scans you'll see some discoloration at the edge of the strip. I have included another 500T example from months back cross processed in cinestill-branded developer that shows a similar anomaly.

In my 500T cross-processing experience, mild color casts are to be expected. Particularly magenta in the highlights. Frankly, I've seen worse with "official" developers. For this reason cross-processing vision 3 is not an ideal control test. I am going to shoot some color plus in the next few days and compare it with a fresh batch of homebrew vs CS developer. That should yield comparable results.

Ideally I would blix with a known chem kit to have a control but alas I'm currently stuck with my ferri bleach/TF-5 combo for the foreseeable future.

I have not re-fixed the stained negs, will update as soon as I get a chance to do so.

 

[koraks]

what you see at the edge of the frame in the "la brega" do happen sometimes when cross processing, I am not sure why, although here it does seem more pronounced. Could related to a mild light leak in my reusable 35mm canisters.

I don't expect this is related to a light leak in the cassettes. It would occur at the long edge of the negative if that was the case, and/or you would have distinct bands of fogging perpendicular to the length of the film. One possible cause is a light leak in the holder/mask you're using for scanning, especially if the same kind of anomaly always shows up at the short edge of the negatives and in the same place. If that's not it, a chemical cause is more likely and that would present the question whether you may have a systematic problem that's not specifically related to C41.

In my 500T cross-processing experience, mild color casts are to be expected.

Shooting tungsten-balanced film in daylight conditions will always induce a dramatic color shift/cast. But what you're running into is color anomalies that vary across the same frame. That can't be explained from the T film shot under D lighting. It's also not a necessary artefact of cross-processing. Cross-processing tends to induce color shifts as well as crossover, but these are again in principle the same across the entire film surface. Variations within the frame and between frames suggests a different set of causes.

The less-compressed example images do look better, although there are indeed some local color casts in them. Something's not going entirely according to plan in those, either.

See if re-fixing helps any.

 

[originalwinslow]

Re-bleached and fixed with fresh chems and double fix time with no effect to the existing stain.

I'm now assuming the stain must have been caused by crossover of developer into the bleach. I have mixed up 1+4 5% vinegar stop bath with 20g sodium sulfite for tomorrow's dev and hope that eliminates the issue. Fingers crossed. I'll get back with the results.

RE: my homebrew developer. Here is a good (bad) example from that first test roll. It's pretty clear from analyzing the color mask that there is an issue. The anomaly along the top section of the frame is also more pronounced. What do we think?

 

[koraks]

I'm not sure what we're looking at. I see a brown band and an unevenly colored, off-white clear band on top of that, and then a strip of black?

 

[originalwinslow]

Sorry, I should've clarified. That is roughly a 200% crop on the top edge of the exposed frame where it meets the unexposed section of color mask. The black is the film holder.

The color mask seems to show some uneven grain structure...or something that looks wonky. At least compared to other reference frames exposed in official chemistry.

Then again, anything cropped 200% might show more imperfections than are actually relevant.

 

[originalwinslow]

Update: Success! (mostly)

It seems the addition of 20g sodium sulfite to the stop as well as 20g/L concentration in a clearing bath before fix has MOSTLY resolved the green fogging/stain in low density negatives. In high-density negatives it is entirely unnoticeable. However, the issue does persist albeit on a lower quantity of total frames in the roll.

I will try extending stop bath time from 30 seconds to 1 minute and see if that completely eliminates it.

Here are two sample images. I fully boosted brightness in NLP to make it much more obvious. Increasing density via editor reduces it to almost unnoticeable but it's there...

It's most likely developer crossover. To completely eliminate other possibilities I'm thinking I could run a bleach bypass test keeping all other steps identical.

Did not expect ferri bleach to be this troublesome.

 

[koraks]

The idea of a bleach bypass test is an interesting one. I'd be curious to hear if that avoids the problem; it'll at least help to identify whether the problem is definitely associated with the bleach.

Did not expect ferri bleach to be this troublesome.

Me neither!

 

[originalwinslow]

Update: Extending stop bath to 1 minute and doubling fix time (just to make sure) did NOT completely eliminate the low-level of stain on the low-density negatives. If anything it is slightly more present. Perhaps stepping up from 1% to 2% acetic acid stop bath acidity is necessary? My next variable adjustment will be the bleach bypass as I mentioned. If no stain after that I will use the "official" FPP ferri bleach from their ECN-2 kit to verify if perhaps my home ferri mix is somehow causing this? If not then it must be the TF-5. fixer, which upon mixing had a pH of 8 which is higher than the "neutral" pH advertised as well as the 6.5 PE had posted here. I have a call in with the formulary to verify with them. Fixer pH shouldn't cause staining as far as I know, but I'm starting to go a little bit crazy here.

I cannot recall if I used sodium bromide or potassium bromide in my 40/25 ferri mix. From what I can tell they are essentially interchangeable if factoring in the difference in bromide concentration. I read on here that fixer "hates potassium ions" but with sufficient washing that shouldn't be an issue. The FPP ECN-2 kit allegedly uses potassium bromide anyway, and RPC substitutes it in both the homebrew developer recipe as well as the ferri bleach. I doubt that has anything to do with this.

 

[koraks]

Yes, I follow what you say. Potassium vs. sodium bromide won't be a major factor in the bleach - nor in the developer if you DIY that. It's a pity that the prolonged stop and fix hasn't made a difference. Yes, do try the 2% acetic acid stop bath, just to make sure, but I don't expect it to be the magic bullet either. And indeed, I don't expect the alkaline fixer to be an issue, but you could try and drop the pH of your fixer by adding a little acetic acid. If you have access to pH indicator paper strips, you could use these to get to pH 6-7-ish.

 

[originalwinslow]

Update: Narrowing it down.

I believe to have concluded that the magenta/green stain was definitively caused by developer carryover to the ferri bleach step.

Yesterday I performed a back-to-back test with bleach bypass and my "standard" c-41. For this test I prepared fresh ferri bleach (40g ferricyanide 25g sodium bromide pH 6.8) as well as fresh TF-5 fixer (pH 8.1). I used the same cinestill developer as previous with 8 rolls run through it. All other steps were kept the same as in my previous devs. Times were 3.5 min developer, 3.5 min bleach, 6 min fix with generous washing in between+sodium sulfite clearing baths.

I shot a roll of identical images on Ultramax 400 with studio lighting for consistency. They are about -2 stops underexposed to guarantee I got full zero-density sections of the negative where the staining is most obvious.

There is no sign of green fogging in the zero-density areas of the bleach bypass negative. In the "standard" dev there is no staining visible to the naked eye, but green is still BARELY present in shadows of the converted positive. It is mild, like digitally blasting the brightness and staring at the screen in a completely dark room mild. So mild that, to the untrained eye, it might simply be attributed to digital noise in the conversion step or an incorrect white balance. So mild that for more than a moment I thought that this case might finally finally be resolved...but I'll let you be the judge.

If deemed necessary my next test is will be to use "official" FPP ferri bleach to ascertain if somehow, someway my home mix is causing this. If it IS my home mix then I don't particularly know what I could possibly be doing wrong with such a simple formula. If the problem persists with FPP bleach then my options are similarly limited. The only thing I can think would be increasing strength/time of stop bath + increasing wash times or trying the 80/20 ferri formula others have shared. In general, I think increased wash time has had the biggest effect on reducing the prevalence of this issue. Although, I have begun to question: if the stain is this mild...do I care? Yes, but patience is fading.

Also, I am left wondering something else. Why the special declaration about crossover staining/sodium sulfite with c-41 that is not mentioned regarding ECN-2? Does CD-4 react differently with the ferri bleach than CD-3? My ECN-2 devs show no signs of this issue while using these same bleach/fix as well as forgoeing any sodium sulfite.

If only PE were here to give the definitive answer...

P.S.

I got in touch with the formulary yesterday. I was wondering if it was normal that my "neutral pH" TF-5 that was testing at pH 8, and also if they had definitive answer as to how long it should take to clear CN film since the instructions do not mention color film. I was told that they were not aware that TF-5 could be used with CN film, and that they do not know (or couldn't tell me) what the pH of TF-5 should be when freshly mixed. I responded that a man named Ron Mowry had written about their product on this forum and explained that TF-5 could indeed be used to clear CN film.

"I knew Ron. He gave a couple presentations here. KA rapid fixer will clear color negatives, but Ron said that KA had it all wrong. Their fixer is acidic, TF-4 is alkaline, and TF-5 is neutral fix which evidently is the best. He invented this fixer and tried to tell them but they were restructuring at the time and didnt care. He told us take this, you should sell it...if he said it can clear CN film then I guess it can."

I didn't get many answers. However, on a personal note it was a very nice interaction. Straight from the horse's mouth.

 

[koraks]

Why the special declaration about crossover staining/sodium sulfite with c-41 that is not mentioned regarding ECN-2? Does CD-4 react differently with the ferri bleach than CD-3?

IDK; I'd expect it to be a problem with both. I never noticed it, but then again, maybe I overlooked it, or my process was different in some key aspect that I can't spot right now.

Their fixer is acidic, TF-4 is alkaline, and TF-5 is neutral fix which evidently is the best.

For the most part, fixer=fixer. The thing about acid fixers and CN film is that the low pH of the fixer can make the dyes appear less colorful; they get (partly) shifted in a so-called 'leuco' state (leuco=white) However, on modern films, this appears to be temporary and the dyes regain their full colors during the wash after fixing. So technically you could even use any old rapid fixer, regardless if it's low, high or neutral pH. There will be differences in fixing speed, but especially in home processing, you can easily fix long enough to give you a safety margin.

Have you tried scanning the regular & bleach bypass negatives side by side in the same pass (using a digital camera setup or a flatbed scanner)? That way you can more easily see the differences. Scan the whole thing as a positive, then do the inversion and color balancing manually.

 

[originalwinslow]

Is there something that you're seeing in terms of discrepancy between the two scans? Aside from the fact that they're dirty, scratched negatives. I didn't treat them particularly carefully.

This is probably worth a separate post but I semi-recently upgraded to using the Negative Supply Co. film holders, and while I think it's better than the Valoi or Essential Film Holder options, I still get some light fogging at the edges of the scan. Since it makes edges of the converted positive brighter my current assumption is that the holder casts a mild shadow/negative fill around the edge of the frame. I cannot figure out why it is more pronounced on one side than the other. I was having this issue particularly with 120 and realized that the light source was slightly angled beneath the holder and this caused one side of the scan to be darker due to increased distance from the subject=inverse square.

However, unlike the 120 holder, the 35mm holder sits directly on the light source.The fogging is visible in these scans. I scanned one of these negatives strips "upside down" relative to the other and when you flip the image one side appears lighter around the edges than in the other. Perhaps this is what you're seeing in terms of discrepancy?

Not sure if I'm explaining this properly. I'm always open to tips as to how to improve the scanning setup. I'm using a d810 with 60mm macro.

 

[koraks]

Is there something that you're seeing in terms of discrepancy between the two scans?

For one thing, the bleach bypass negs have the same contrast as the normal ones. That can't possibly be right, so something is getting evened out in the process and that means you're not really doing a 1:1 comparison.

 

[originalwinslow]

Yes I do see what you mean. The contrast seems to be similar in both, although I see MAYBE slightly more shadow gradient/falloff in the regular dev than in the bleach bypass.

This is also the most high-contrast lighting setup possible. Perhaps for that reason the difference is harder to see? I can try running the two 35mm strips side by side in the 120 holder. I have an old flatbed I could set up as well if that doesn't work. Admittedly I don't have a lot of experience comparing bleach bypass to regular c-41 in my own tests.

Either way, I do not think the presence of green fogging in one and not the other is an error of the Negative Lab Pro conversion algorithm. I've worked with NLP for 5 years and never seen this before.

 

[koraks]

I can try running the two 35mm strips side by side in the 120 holder.

Do that, see what happens. It'll help removing some 'maybes' from the equation.
The inherent problem with scanning as a positive and unleashing stuff like NLP on the images is that you don't know what you're really looking at anymore. Things get adjusted one way or another, making it impossible, for instance, to tell whether you're dealing with a green cast along the edges or a magenta cast in the center etc. If you scan the images in such a way that every scan is in principle the same and the only variation is in the negatives, it becomes easier to tell how the negatives really compare to each other. It still doesn't give you an absolute assessment, but you'll at least be able to work with a relative benchmark.

 

[lamerko]

Since you are doing a "DSLR scan", you need to lock in the camera settings - color balance (neutral profile), ISO, aperture, speed. It is true that the RAW files only contain instructions, but if you want to do a visual comparison, leave the conversion internal to the camera and compare the JPEGs.