How to judge C-41 processing result

[foc]

What I'm saying is if you run a tightly controlled process, and then run expired film through it, the entire imaging chain is still out of control. I don't really see the benefit of going through the lengths of test strips and densitometry for a development process if you end up running expired film through it anyway.

+1

 

[Anon Ymous]

+1

+2

 

[pentaxuser]

I only do rotary processing these days so I am not able to compare with results from intermittent agitation. Sorry about that. I can only tell that the rotary processing (constant drum rotation) seems to cause over oxidation to the developer. You can see bubbles, lots of it, when the developer is poured out of the JOBO drum. The bubble obviously contains lots of oxygen.

Thanks. I may have misunderstood what you said. I had wrongly thought that something had changed on one occasion with your Jobo and that the change had caused over agitation on that one occasion.

Yes there is always bubbles in my Jobo drum but they are there irrespective of whether I do inversion( a la the Ilford or Kodak regime or use rotary. Cutting the frequency of agitations might lower the amount of bubbles but equally might not then be enough for C41 films in 3 mins 15 secs to achieve full development

I have no idea how much extra air is created in the developer but I am sure this is taken into account when the developer maker suggests its total recommended usage. The ultra-conservative approach might be to use each developer amount once only then dump; the conservative approach might be not to exceed the recommendation given by the maker as to how many films can be developed from whatever the kit size is. However there are those who claim that there is a built-in very conservative safety margin that can be exceeded.

Does the last strategy guarantee good control and the best outcome. Only the user can decide but if you are looking for the best outcome then as others have said using expired film is introducing a major unknown into the process

pentaxuser

 

[koraks]

You can see bubbles, lots of it, when the developer is poured out of the JOBO drum. The bubble obviously contains lots of oxygen.

The bubbles have nothing to do with oxidization of the developer, though. The bubbles are there because your developer contains a surfactant that's intended to allow for even wetting of the film during the typically short development times of C41 film. A side-effect of this is some foaming. It's a bit like dishwashing detergent.

JOBO rotation does not cause problematic oxidization of C41 developer as long as the developer isn't used past its stated capacity to begin with, and/or it is sufficiently replenished.

C41 developer is typically rather heavily loaded with hydroxylamine sulfate which acts as an oxygen scavenger. It takes *a darn lot* of oxidization to use up all the HAS in the developer! There's no way a normal constant agitation process in drums will get you even close to that point. It's a non-issue.

ECN2 developer is a bit of a different story since it typically doesn't contain any HAS (it could be added, I suppose), but even this doesn't appreciably deteriorate in a typical constant agitation scheme. Certain B&W developers are also different, especially the staining ones (e.g. 510 pyro, Rollo, pyrocat, etc.), since they necessarily have very little to no anti-oxidants to promote staining and tanning. But all this is a different universe from C41 processing.

There is no such thing as 'over-agitation' in C41 processing. The process is designed for constant agitation and it's by definition impossible to agitate more than all the time! The difference between briefly intermittent agitation (e.g. every 15 seconds) and constant agitation on C41 film will be close to zero. Potential agitation-related problems include:

1: Insufficient agitation; e.g. less than a vigorous agitation cycle every 30 seconds (which is already on the risky side given the brief development times). This can result in unevenness and reduced gamma. The latter will likely go unnoticed in a typical hybrid workflow where the scanning and digital post processing will hide small anomalies. Unevenness is of course a different story and usually fatal in that it cannot be corrected.

2: Uneven agitation; e.g. flow patterns across the film that result in more agitation in some areas than in others. This relates to reel and film geometry, which can create different flow/turbulence patterns in different areas of the film. A notable example of this is illustrated by the two flaps included with the present Jobo 2509N reels for 4x5 film; without these flaps, the uneven agitation pattern can cause 'wings' of varying density along the film edges of sheet film under certain conditions. There's also a very rare possibility of 'wagon ruts' on roll film, but I've only heard of one or two cases that seemed somewhat verifiable.

 

[Steven Lee]

There is no such thing as 'over-agitation' in C41 processing. The process is designed for constant agitation and it's by definition impossible to agitate more than all the time!

One would think so. But take a look at Z-131 page 5-31, where Kodak plots RGB density variations caused by under/over agitation. If it made to the process control section of the C-41 process manual, it must be a thing!

 

[koraks]

One would think so. But take a look at Z-131 page 5-31, where Kodak plots RGB density variations caused by under/over agitation. If it made to the process control section of the C-41 process manual, it must be a thing!

But interestingly, in the accompanying text, the issue of overagitation is not addressed at all, while some suggestions for fixing underagitation are mentioned. I guess that if it's a thing, it's not really a thing that in practice required much in the way of problem solving.

Mind you that I made my comment in the context of home-style rotary processing. It's literally impossible to overagitate that way. I imagine you'd have to shake the tank like a cocktail shaker for 3m15s straight to make a real dent. Fortunately, that's not something rotary processors are known to do. Or unfortunately...?

 

[RPC]

Koraks, please show where Kodak has ever said C-41 was designed for constant agitation. Their own literature describes processes that use intermittent agitation,
and PE said they always used intermittent agitation in testing at Kodak. Constant can be used, if it is controlled properly.

 

[MattKing]

Koraks, please show where Kodak has ever said C-41 was designed for constant agitation. Their own literature describes processes that use intermittent agitation,
and PE said they always used intermittent agitation in testing at Kodak. Constant can be used, if it is controlled properly.

C-41 was designed to be fully compatible with continuous agitation, because a large percentage of minilab machines moved the film continuously through the baths.
I wouldn't say that C-41 was optimized for continuous agitation, as compared to other options.
.

 

[Steven Lee]

I was half-joking because Koraks is correct at pointing out that it's impossible to over-agitate in a JOBO. I tried all kinds of rotation speeds/directions and had no trouble hitting process control aim values on control strips. The only noticeable change I observed were occasional appearance of surge marks on 35mm rolls.

But if Kodak felt the need to describe the effect of over-agitation in the process control chapter, I'd assume there must be a way to do it.

 

[koraks]

Koraks, please show where Kodak has ever said C-41 was designed for constant agitation.

See for instance how they describe optimal conditions for nitrogen burst agitation, which they prescribe as 2 second bursts at 10 second intervals. This works out as a developer that's in motion all the time. An alternative is through turbulation bars which would typically be in motion constantly as well.

So yes, Kodak really does very explicitly prescribe conditions of permanent solution motion for C41 developer. They also emphasize conditions for larger machines/labs than a typical home situation. Approximating the kind of turbulence Kodak prescribes for C41 processing in a home setting works out as agitating as frequently as possible and ideally constantly, for instance in a rotary processor.

 

[pentaxuser]

Just a pity perhaps that in any mention of over agitation Kodak or whomsoever mentions it do not bother to cite the way this over agitation is achieved. However any forum seems full of "throwaway" comments that are never explained or backed up and yet despite this, such comments gather momentum which seem to be remembered and repeated

Still we can gather some comfort that such throwaway lines are the "stuff" of lively exchanges

pentaxuser

 

[RPC]

Koraks, again, both types of agitation can be and are used so I don't see how your statement is true that C-41 was designed for continuous agitation. It is misleading.

PE has a different way of looking at nitrogen burst agitation. See this thread:

https://www.photrio.com/forum/threads/inversion-vs-rotation-for-c-41-developing.117655/

Someone else in the thread also said what you said about it being designed for continuous agitation, but PE clarifies it, that it was designed for both.
I have seen threads where some had to adjust their rotary processor speed to get the best results.

 

[mtjade2007]

Very much so. Please read back what I wrote; you'll notice we agree on scanning and optical printing, and the color corrections needing to be done in both workflows.
What I wanted to caution against, is an often-heard mantra: "this is what I get straight from the scanner and it looks pretty good, so my film and processing are very good." That logic doesn't add up in many ways. The opposite also doesn't work: "without doing adjustments to the image I get from the scanner, the result is crap, so there's something wrong with my film processing". The simple truth is that in a typical consumer scanning setup, what you get from the scanner says nothing about the quality of the film or the processing. One can get decent scans from horribly compromised film and processing (ECN2 film cross-processed in C41 developer is a popular one these days) and vice versa.

I ran into some processing failures recently. I dumped all 3 chemicals and refilled with freshly prepared ones. It was cheap for a liter of each of the 3 chemicals. It sort of quickly helped me identify that my expired film wasn't responsible for the failure. But did it? I have been debating with myself should I trust my scanner despite it is a $2k Minolta film scanner. Or why should I care if my final images are decent that please me? So far I am not convinced that my film scanner lies. The scanner is user adjustable. I think the user adjustment is why a scanner lies. For example ROC is a scanner feature. If you turn it on the scanner will indeed hide the problems of problematic films. I don't use ROC.

By the way, I did a test of shooting a same scene with under, accurate and over exposures. When I scan the film the final images did show 3 scans, one dark another too low density and the 3rd just about right. In addition the histograms of the 3 image do indicate one shift toward left (under exposure) and one in the middle and the other toward right (over exposure). The one with correct exposure did not occupy the entire density range (0 to 255). All these told me the scanner scanned the 3 frames of film faithfully. It did not hide under exposure nor over exposure. It did not do auto level adjustment either. A good scanner is supposed to be like that.

 

[mtjade2007]

I believe JOBO drums rotation at 75 RPM is in fact an oxygenation act especially the drum contains very small quantity of developer. I haven't seen any ill effects except I did feel my developer never keeps long and the capacity lowered. I could develop only 4 220 rolls per lier of developer. Kodak did advise not to replenish the developer used in rotary processors. That seems to say the developer is too oxidized and can not be replenished normally.

 

[koraks]

All these told me the scanner scanned the 3 frames of film faithfully.

'Faithful' is a very fickle concept in the context of scanning color negatives. Faithful to what? You point out that three differently exposed frames show expected differences in value distribution. But a truly 'faitful' scan of a color negative would be an overall brown-orange image with a relatively low-contrast and inverted color image on it. You appear to refer to inverted scans that look natural at least to some degree, and this implies that some kind of color correction has taken place. Photograph a color negative and invert it without any adjustment, and the image will be far from natural looking. The scanner (and especially its accompanying software) makes some kind of judgement based on image content as to what is supposed to be natural, usually based on things like assumptions on density distributions based on statistical analysis. It's an approximation, and the vast majority of scanners are demonstrably inconsistent - which is a good thing, because this makes them far more user-friendly than if they would have interpreted every negative according to some arbitrarily chosen gold standard.

Think about it - if there were an absolute reference, what should it be? Fresh Kodak Gold 200? Or Ektar 100? Or something else? Then what happens if the user scans a strip of expired film with higher fog? They should get washed out images with reduced shadow densities in the positive, due to the high b+f in the negative. You appear to not get that with your expired film, which is an immediate sign that your scanner, too (like virtually all others) does an 'autocorrect' on image data.

All this automatic adjustment isn't such a problem, though. The only implication is that a scanner, unless it's run in a color-calibrated mode that disables all automatic adjustments, which is likely impossible with most scanners, can not be used as an absolute reference for determining process quality. A film scanner is not a densitometer.

Kodak did advise not to replenish the developer used in rotary processors. That seems to say the developer is too oxidized and can not be replenished normally.

This is not just due to oxidation during development. Run the math on how much oxygen the developer could physically absorb during a development run of a few minutes and how much HAS there is in a typical C41 developer. It's impossible to use up the HAS under those conditions. The developing agent will remain protected against aerial oxygen uptake. The reasons why Kodak advises against replenishment in such cases is most likely because the total volume in a typical home/small tank setup is so small that it's virtually impossible to get a stable developer activity under conditions of replenishment, given the different types of film run through it (the gelatin emulsion itself interacts with the developer, especially influencing its pH), the overall silver density developed in the film, the byproducts that leach out of the film (especially halides) during development, not to mention storage of working solutions between development sessions. The latter is not a concern in a (more or less) continuously used setup as you'd find in a volume lab, where the total working volumes are also larger (easily a few liters for a small machine) and where a heterogeneous mix of films tends to even out the other effects I mentioned.

A larger volume is simply more stable and therefore easier to keep in check with a replenishment system. A tiny (and intermittently used) system such as a home processing situation is easily thrown off-balance and will easily drift far out of spec if you try to reuse and replenish it. It's not so much due to oxidation during development, but the entire set of parameters of the system.

 

[MattKing]

Kodak did advise not to replenish the developer used in rotary processors. That seems to say the developer is too oxidized and can not be replenished normally.

Emphasis on "normally".
Whenever you read anything like a colour datasheet from Kodak, it is important to remember that it is targeted toward a commercial lab audience.
If Kodak was unable to make recommendations for how to replenish developer used in a variety of rotary processors that would result in relatively simply maintained consistent results, they would recommend against such use.
The recommendation against may be related to oxidation, or variability between the available options, or other factors that might come to mind.
It may be that using a rotary processor with tanks that are closer to being filled may solve the problem. It may be that standardizing on one type of tank and reel may solve the problem. The rotation speed chosen may be critical - or???

 

[foc]

In a dip & dunk C41 processor, the developer tank is narrow but deep. With a strong nitrogen burst of 2 seconds every 10 seconds and the bubbles traveling up through the tank, the developer is agitated. There will be some residual agitation after the bubbles have surfaced and then the next burst starts the agitation process over again. A rhythm of almost continuous agitation is introduced.

In a minilab leader card processor, the developer in the tank is circulated by a pump all the time. The film is pulled through the tank, along guide rollers through a continuously agitated developer solution.

 

[pentaxuser]

Koraks, again, both types of agitation can be and are used so I don't see how your statement is true that C-41 was designed for continuous agitation. It is misleading.

Here's a question that has occurred to me. If inversion is OK i.e produces the same negative to the same quality that continuous rotary processing does then is there an appreciable range of agitation that will produce the same negative. It would seem like it.

I presume that on the same basis the recommendation that development time be reduced for continuous rotary processing by about 15% only applies to b&w film otherwise the inversion time for C41 should be increased by say 15% to about 3 mins 45 secs instead of 3 mins 45 secs?

Is there something about colour negs developed in C41 that makes no difference to the result whether you invert or continuously rotate?

Interestingly or not as the case may be I could not find any mention of inversion in the data sheets for XP 2 Super processing whereas in HP5+ there is the usual recommendation to decrease time by up to 15% I have no idea what I can conclude from that


Thanks

pentaxuser

 

[RPC]

Is there something about colour negs developed in C41 that makes no difference to the result whether you invert or continuously rotate?

C-41 is designed for a standard development time of 3' 15''. The type as well as rate of agitation does make a difference, therefore results are controlled by properly adjusting agitation rates for each during development time.

 

[mtjade2007]

Emphasis on "normally".
Whenever you read anything like a colour datasheet from Kodak, it is important to remember that it is targeted toward a commercial lab audience.
If Kodak was unable to make recommendations for how to replenish developer used in a variety of rotary processors that would result in relatively simply maintained consistent results, they would recommend against such use.
The recommendation against may be related to oxidation, or variability between the available options, or other factors that might come to mind.

That's exactly what my point was, oxidation of the developer. Constant rotation (despite back and forth rotation) by rotary processors (JOBO as an example) and a small volume of developer used in the drum facilitates a high ratio between exposed to air surface area of the developer and the developer volume, which as a result increases the reaction between air and the CD-4 in the developer. I don't remember the exact words by Kodak but the statement clearly tells me not to replenish developer used in rotary processors. My experience did confirm the reality to not replenish my developer. I also realize the developer will not keep long even after only one use through my JOBO processor.

It may be that using a rotary processor with tanks that are closer to being filled may solve the problem. It may be that standardizing on one type of tank and reel may solve the problem. The rotation speed chosen may be critical - or???

Yes, if the drum is fully filled the oxidation of the developer may be minimized to a degree similar to dip and dunlk processors.

 

[mtjade2007]

'Faithful' is a very fickle concept in the context of scanning color negatives. Faithful to what? You point out that three differently exposed frames show expected differences in value distribution. But a truly 'faitful' scan of a color negative would be an overall brown-orange image with a relatively low-contrast and inverted color image on it. You appear to refer to inverted scans that look natural at least to some degree, and this implies that some kind of color correction has taken place. Photograph a color negative and invert it without any adjustment, and the image will be far from natural looking. The scanner (and especially its accompanying software) makes some kind of judgement based on image content as to what is supposed to be natural, usually based on things like assumptions on density distributions based on statistical analysis. It's an approximation, and the vast majority of scanners are demonstrably inconsistent - which is a good thing, because this makes them far more user-friendly than if they would have interpreted every negative according to some arbitrarily chosen gold standard.

The question here is if moving images from one medium (such as a negative) to another (such as a digital file viewable on a monitor) can be done without the image information being altered. It is easy to say a scanner, a technology based tool, induces inconsistency from the image move transition. Of course it does. However, the 3 shot example I mentioned and the scans was to describe that it looks my scanner did not correct (automatically) the under and over exposed films. Their histograms are showing where they should reasonably be. If the scanner software did automatically some adjustment to be kind to the users the histogram will reveal that. It is a mystery if colors are altered and users have no idea what alteration had happened is purely caused by the scanner software. Keep in mind the gamut (color space) of a negative and a monitor are very different. There must be a very complicated algorithm in the scanner design engineer's mind to deal with the media difference. But whatever it is there is not an intention to make adjustment to alter the image data in my scanner. I did not mention the gamut of the Scanner's CCD,did I? Thank about if it is factored in. In my opinion, optical printing exists a similar media move issue. There is always differences between before and after the move transaction of the image data.

Think about it - if there were an absolute reference, what should it be? Fresh Kodak Gold 200? Or Ektar 100? Or something else? Then what happens if the user scans a strip of expired film with higher fog? They should get washed out images with reduced shadow densities in the positive, due to the high b+f in the negative. You appear to not get that with your expired film, which is an immediate sign that your scanner, too (like virtually all others) does an 'autocorrect' on image data.

All this automatic adjustment isn't such a problem, though. The only implication is that a scanner, unless it's run in a color-calibrated mode that disables all automatic adjustments, which is likely impossible with most scanners, can not be used as an absolute reference for determining process quality. A film scanner is not a densitometer.



This is not just due to oxidation during development. Run the math on how much oxygen the developer could physically absorb during a development run of a few minutes and how much HAS there is in a typical C41 developer. It's impossible to use up the HAS under those conditions. The developing agent will remain protected against aerial oxygen uptake. The reasons why Kodak advises against replenishment in such cases is most likely because the total volume in a typical home/small tank setup is so small that it's virtually impossible to get a stable developer activity under conditions of replenishment, given the different types of film run through it (the gelatin emulsion itself interacts with the developer, especially influencing its pH), the overall silver density developed in the film, the byproducts that leach out of the film (especially halides) during development, not to mention storage of working solutions between development sessions. The latter is not a concern in a (more or less) continuously used setup as you'd find in a volume lab, where the total working volumes are also larger (easily a few liters for a small machine) and where a heterogeneous mix of films tends to even out the other effects I mentioned.

A larger volume is simply more stable and therefore easier to keep in check with a replenishment system. A tiny (and intermittently used) system such as a home processing situation is easily thrown off-balance and will easily drift far out of spec if you try to reuse and replenish it. It's not so much due to oxidation during development, but the entire set of parameters of the system.

Oxidation prevention by HAS is static. Agitation is dynamic. More agitation causes more oxidation.

 

[pentaxuser]

C-41 is designed for a standard development time of 3' 15''. The type as well as rate of agitation does make a difference, therefore results are controlled by properly adjusting agitation rates for each during development time.

Ah so I am right that when any article mentions C41 inversíon agitation it should say that the time of 3 mins 15 secs needs extending? Do articles or Kodak say this and what is it they should say in terms of an extension of time?

It's just that I can recall seeing any such recommendation anywhere including here on Photrio

Thanks in anticipation of an answer

pentaxuser

 

[RPC]

Ah so I am right that when any article mentions C41 inversíon agitation it should say that the time of 3 mins 15 secs needs extending? Do articles or Kodak say this and what is it they should say in terms of an extension of time?

It's just that I can recall seeing any such recommendation anywhere including here on Photrio

Thanks in anticipation of an answer

pentaxuser

I don't know how you got that from what I said. I said you adjust the results with agitation rates for each agitation type, with standard time of 3'15".

 

[koraks]

The question here is if moving images from one medium (such as a negative) to another (such as a digital file viewable on a monitor) can be done without the image information being altered.

That's an easy one to answer. Obviously, it can't!

In my opinion, optical printing exists a similar media move issue. There is always differences between before and after the move transaction of the image data.

So apart from the other things you said, which I understand, but only partly agree with, the question is: what do you take away from this?

You started with the question how to judge your C41 development process. For many reasons, relying on the output of a scanner isn't a very good way to do this unless it's part of a carefully calibrated imaging chain, which is likely beyond the means or necessity of a home user. An approach relying on optical printing is similarly challenging.

The question remains how relevant it is to know the quality of your C41 development process beyond the obvious informal assessment of just producing images and seeing if they meet your needs. I understand your imaging chain is purely a hybrid one, where you use film for capture and then scanning to proceed into digital post production. This means that there are roughly speaking four areas where the quality of the output is determined (or, if you're cynical: can be messed up):
1: Choice of materials; film & chemistry, but also equipment like scanner and development tanks etc.
2: Film processing
3: Scanning
4: Digital post processing

To an extent, all of these items are black boxes. But some have more potential for both mess-ups and quality gains than others. Let's see:
#1 is a simple one: we have very little influence on the materials, so the best shot we have is to buy materials from a reputable manufacturer and use them before they go bad.
#2 is for the home user likewise a black box for all intents and purposes, because even if you determine that the process is out of spec, it's often difficult to figure out why. On the other hand, a process that's run on decent materials (see #1) and according to the manufacturer's instructions combined with common sense tends to perform more than adequately for virtually every purpose.
#3 you can either work in a color-managed workflow using calibration targets, but the problem is that this only goes so far and relies on targets on the exact type of film you're using (and a scanner that actually supports such a workflow). The alternative is to experiment with various scanning settings to find something that seems as consistent as possible, and then hope for the best. Outsourcing scanning is a third option, but this makes the black box only blacker still.
#4 this is a part where the artist/photographer has a massive degree of control and opportunities to steer the result into virtually any imagined direction. The limitations are posed virtually only by the user's abilities/competence, given that he starts with something that's halfway decent (i.e. evenly developed film with at least somewhat useful color data).

Given the fact that your odds of actually making a difference in terms of the end result are very limited in #1 through #3, with basically your best shot being "just do as it says on the tin", it seems very obvious to me what the question should really be about.

So my honest answer to the initial question you asked, is: go read some books on color grading. As long as you can produce negatives that don't have horribly apparent defects, this is the one area in your workflow where an investment in time and perhaps some software is really going to pay off dramatically.

You perhaps now also understand why the vast number of photographers have transitioned to digital. It reduces 3 pcs. of black boxes to just one, leaving their hands free to focus on the fourth, which actually really makes a difference. This is not me being cynical about the possibilities of analog photography etc. It's just a sober observation of how people who are serious about the craft and approach matters rationally produce images.

An irrational approach I find very interesting and in fact I would encourage if you're inclined to it. But if you choose that route, don't tire yourself with boring questions about how to get your C41 process running on spec.

Oxidation prevention by HAS is static. Agitation is dynamic.

It's unclear what you mean by 'static' and 'dynamic' in this context. The chemical processes that occur in an agitated developer are very dynamic indeed; there's nothing static about them. This is true for all processes within the developer given the innate mobility of molecules at higher than absolute zero temperatures. HAS is not the chemical equivalent of a piece of saran wrap being pulled over a pudding or something. Its protection is as 'dynamic' as can be. You seem to doubt that the amount of HAS present in a commercial C41 developer is sufficient to protect a small volume in a rotary tank from getting into trouble in one (or even a couple) of development runs. This is not the case.

Also, in my experience, C41 developer that's used (with constant agitation) preserves just fine and will work virtually the same weeks after its first use. It's something I don't recommend because repeated use will eventually result in drift, but the developer doesn't magically oxidize all of a sudden after it's been used once. This is evidenced by the lack of color change - don't be confused with sensitization and antihalation dyes from the film leaching into the developer.

Really, you're making far too much of this supposed oxidization problem. If you use your developer one shot, or even twice, it's not an issue. Not even if you go crazy shaking it during processing (it evades me why you would, however). Storage conditions are far more relevant.

TL;DR: it's very easy to get lost in details that turn out to be irrelevant, and to complicate matters that are unproductive. In my view, you're heading down this path very fast. That's OK, but if you want to make images, this is not really the way to go.

 

[mtjade2007]

That's an easy one to answer. Obviously, it can't!



So apart from the other things you said, which I understand, but only partly agree with, the question is: what do you take away from this?

You started with the question how to judge your C41 development process. For many reasons, relying on the output of a scanner isn't a very good way to do this unless it's part of a carefully calibrated imaging chain, which is likely beyond the means or necessity of a home user. An approach relying on optical printing is similarly challenging.

I was saying I am seeking a quick and easy way for... I did not look for answers involving high end lab machines and instruments. I anticipate to take away a quick and easy way and that's a more interesting subject to discuss for me. I have several color analyzers, densitometers (B&W and color), PH meters that are accumulating dusts. I almost plunged into buying a lab in the early 90's. Glad that I moved away from that direction.

The question remains how relevant it is to know the quality of your C41 development process beyond the obvious informal assessment of just producing images and seeing if they meet your needs. I understand your imaging chain is purely a hybrid one, where you use film for capture and then scanning to proceed into digital post production. This means that there are roughly speaking four areas where the quality of the output is determined (or, if you're cynical: can be messed up):
1: Choice of materials; film & chemistry, but also equipment like scanner and development tanks etc.
2: Film processing
3: Scanning
4: Digital post processing

The quality C-41 development knowledge that strictly falls into the Kodak Bible guideline is irrelevant to me at the current state of the hobby. Thank you for your suggestions.

To an extent, all of these items are black boxes. But some have more potential for both mess-ups and quality gains than others. Let's see:
#1 is a simple one: we have very little influence on the materials, so the best shot we have is to buy materials from a reputable manufacturer and use them before they go bad.
#2 is for the home user likewise a black box for all intents and purposes, because even if you determine that the process is out of spec, it's often difficult to figure out why. On the other hand, a process that's run on decent materials (see #1) and according to the manufacturer's instructions combined with common sense tends to perform more than adequately for virtually every purpose.
#3 you can either work in a color-managed workflow using calibration targets, but the problem is that this only goes so far and relies on targets on the exact type of film you're using (and a scanner that actually supports such a workflow). The alternative is to experiment with various scanning settings to find something that seems as consistent as possible, and then hope for the best. Outsourcing scanning is a third option, but this makes the black box only blacker still.
#4 this is a part where the artist/photographer has a massive degree of control and opportunities to steer the result into virtually any imagined direction. The limitations are posed virtually only by the user's abilities/competence, given that he starts with something that's halfway decent (i.e. evenly developed film with at least somewhat useful color data).

Given the fact that your odds of actually making a difference in terms of the end result are very limited in #1 through #3, with basically your best shot being "just do as it says on the tin", it seems very obvious to me what the question should really be about.

So my honest answer to the initial question you asked, is: go read some books on color grading. As long as you can produce negatives that don't have horribly apparent defects, this is the one area in your workflow where an investment in time and perhaps some software is really going to pay off dramatically.

You perhaps now also understand why the vast number of photographers have transitioned to digital. It reduces 3 pcs. of black boxes to just one, leaving their hands free to focus on the fourth, which actually really makes a difference. This is not me being cynical about the possibilities of analog photography etc. It's just a sober observation of how people who are serious about the craft and approach matters rationally produce images.

I anticipate the life of photographic film and associated chemicals to eventually phase out. But before that happens I don't want to pass the remaining opportunity to enjoy the fun it offers. I left photography once for many years. The productivity of darkroom work simply wore me out. The introduction to the market of film scanners brought me back into it. The high tech way of transitioning images from film to digital file is something that deserve film shooters to dig deep into it and benefit from it fully.

An irrational approach I find very interesting and in fact I would encourage if you're inclined to it. But if you choose that route, don't tire yourself with boring questions about how to get your C41 process running on spec.


It's unclear what you mean by 'static' and 'dynamic' in this context. The chemical processes that occur in an agitated developer are very dynamic indeed; there's nothing static about them. This is true for all processes within the developer given the innate mobility of molecules at higher than absolute zero temperatures. HAS is not the chemical equivalent of a piece of saran wrap being pulled over a pudding or something. Its protection is as 'dynamic' as can be. You seem to doubt that the amount of HAS present in a commercial C41 developer is sufficient to protect a small volume in a rotary tank from getting into trouble in one (or even a couple) of development runs. This is not the case.

Also, in my experience, C41 developer that's used (with constant agitation) preserves just fine and will work virtually the same weeks after its first use. It's something I don't recommend because repeated use will eventually result in drift, but the developer doesn't magically oxidize all of a sudden after it's been used once. This is evidenced by the lack of color change - don't be confused with sensitization and antihalation dyes from the film leaching into the developer.

Really, you're making far too much of this supposed oxidization problem. If you use your developer one shot, or even twice, it's not an issue. Not even if you go crazy shaking it during processing (it evades me why you would, however). Storage conditions are far more relevant.

TL;DR: it's very easy to get lost in details that turn out to be irrelevant, and to complicate matters that are unproductive. In my view, you're heading down this path very fast. That's OK, but if you want to make images, this is not really the way to go.

One can agitate the film aggressively or moderately thus the oxidation of the developer varies dynamically. HAS provides a long term protection to the developer when it is in the state of storage in the bottle. That is static. I apologize if I don't use the word appropriately.