How to judge C-41 processing result

Is there a quick and easy way to judge the result of a C-41 process? A subsequent wet print process (RA-4 as an example) is probably the ultimate way but not everyone has a wet darkroom, time and expertise to go that way. Film scanning is said to be a very wrong way to go in this forum. So is there any other way? How does everyone judge his/her processing result and do the adjustment or correction (if possible of course)? If a wet print is not produced it leaves only the digital way which has to be the film scanning. But if it is a very wrong solution what is a better way? A quick and easy answer to this question will be a huge help for C-41 processing DIYers to avoid or reduce processing errors. Hope to hear from many experts soon. Thanks.

mtjade2007 said:

Film scanning is said to be a very wrong way to go in this forum.

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What makes you think so?

Regardless of it, there's IMHO, no quick and easy way to check for process errors. Negatives may look fine, but have significant crossover. I'm not talking about very obvious ones, like inadequate bleaching or fixing.

mtjade2007 said:

A subsequent wet print process (RA-4 as an example) is probably the ultimate way

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Even this is doubtful given the fact that currently manufactured color papers are not exactly matched to c41 film. You will get some crossover especially in magenta & green with a properly processed C41 negative.

As @Anon Ymous says, there's no quick and easy way.

I'd consider two routes:

1: if the negatives yield the desired final images, they're by all accounts good enough, even if not "officially on spec". What matters is if the result meets the requirements of the photographer and/or printer and/or artist. One might call this a pragmatic approach.

2: the alternative would be to obtain or make a "gold standard" negative on the film used and then use that as a reference in subsequent testing, which would typically rely on some form of density measurements on processed film. This would have to involve stuff like test charts photographed under controlled conditions etc. This is a more theoretical approach.

While (2) might feel "safer", it's also very challenging to get right, and the effort may overshoot the target of a result that's simply good enough. For this reason, I'd consider (1) unless there's a compelling reason to make things more complicated.

I think the obvious answer is C-41 control strips and a densitometer. That's a $500 investment though. I've been postponing it for years and now I can finally sleep well, knowing that my results are exactly what Kodak engineers wanted me to have.

1. http://www.acurad.net/ to get a calibrated color densitometer, they're about $400 IIRC
2. Get Fuji CN-16 control strips. They're cheaper than Kodak's and sold in smaller quantities.
3. Fuji's control strip manual, google "CN-16 Fuji PDF"
4. Develop a habit of adding a control strip to your film every time you make an adjustment.

It helps if you have available a reference setup with a consistent light source and a consistent target - something like a Colourchecker.
And that you reasonably regularly include a reference frame on the rolls you process.

Thanks for the replies. Good points, Koraks. Anon, I may be wrong about scanners.

C-41 process looks really simple but it is really very complicated considering all causes that could lead to a failure.

I ran into a problem recently and wasted a lot of time and a good number rolls of film. The films were outdated and my Kodak Flexicolor chemicals were very old as well. That really made things more complicated to troubleshoot. It's a hobby to me so I am trying to be not wasteful of the expired stuff. I still believe there is something identifiable responsible for the failure. I need to identify if it was the outdated film or any of the old Kodak chemicals that has gone beyond usable. I eventually solved the problem. I dumped all developer, breach and fixer. Refilled my JOBO rotary processor with newly prepared ones (same old aged Kodak chemicals). Tested the process with a short piece of expired Kodak NC160. The scanner output looked OK without any adjustment during and post scanning. What a relief that my films and chemicals are still usable.

But I still have no idea what went wrong. That's OK. as long as I now get OK looking images. The cause of my recent failure is very likely because of overly reuse of the juice. They are dumped and no more. What I am concerning is if it is really OK and I am not fooled by my scanner. I think my expired NC160 is in good condition. It is very usable. My chemicals are usable too. I am using 5 grams of CD-4 to replace Part C for each liter of the developer. However these positive thinking better have a more scientific backing by looking into if my scanner did something to fool me.

Here is an image out of my scanner without any adjustment done to the scanner. Basically all the adjustment, if there is any, is not by me. The image actually does not look great. Colors are somewhat muted (the NC look?). Very flat with no dynamics. The histogram does show everything falls between 0 and 255 (RGB density). The colors may not be accurate. There is no skin tone for evaluation so I am not concerned about the accuracy of the colors.

MattKing said:

It helps if you have available a reference setup with a consistent light source and a consistent target - something like a Colourchecker.
And that you reasonably regularly include a reference frame on the rolls you process.

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Yes, Matt. I do hope, however, an even easier method than that exists. What you suggested are harder than thought. Thanks for the suggestion.

Steven Lee said:

I think the obvious answer is C-41 control strips and a densitometer. That's a $500 investment though. I've been postponing it for years and now I can finally sleep well, knowing that my results are exactly what Kodak engineers wanted me to have.

1. http://www.acurad.net/ to get a calibrated color densitometer, they're about $400 IIRC
2. Get Fuji CN-16 control strips. They're cheaper than Kodak's and sold in smaller quantities.
3. Fuji's control strip manual, google "CN-16 Fuji PDF"
4. Develop a habit of adding a control strip to your film every time you make an adjustment.

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Yes, this will clearly tell if everything is in spec. That's a long way to get the result though. Thanks a lot.

I did a quick post processing to the initial scanner output. The adjustment I did were simple level (contrast and mid tome) tweak only. Here is the image after the adjustment. It looks much pleasing now. But it is not the look of Kodak NC any more. It's more like Kodak UC. It's a manual post tweaking, not by the scanner. But despite the picture looks much pleasing now it does not mean much in terms of if the film was processed correctly. The question remains if the scanner and my post processing actually masked off the errors. Can anyone share his/her thoughts if I can judge by looking at this final image if my processing is good and no need of any concern. Or I should consider the picture good enough as Koraks suggested. I do feel good about the final result.

This is probably too much.

mtjade2007 said:

Yes, Matt. I do hope, however, an even easier method than that exists. What you suggested are harder than thought. Thanks for the suggestion.

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The best/easiest way to ensure consistent lighting is to employ an electronic flash with built in "auto" exposure in a table-top setup.

@mtjade2007 I have another idea for you. If you don't want to use control strips, you can get yourself an X-Rite color target and take a photo of that target under controlled lighting. Matt's suggestion of using flash is a good one. Then, you can develop a roll at a well-known reputable lab. Now you have a reference. Scan it and save.

When you develop your own film, make the same exposure. When you scan your films, you can compare the RGB values of the grey patches of the target.

Essentially this very similar procedure to control strips but less precise, and it depends on using the same emulsion.

MattKing said:

The best/easiest way to ensure consistent lighting is to employ an electronic flash with built in "auto" exposure in a table-top setup.

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Yes, that test shot was shot indoor with a 200ws strobe. I used a Minolta flash meter to determine the required exposure. This setup will be the reference standard for future evaluation of my film and processing. The only question in mind is if it is the right way to evaluate the image from the scan. I guess I have no other choice that is quick and easy.

Steven Lee said:

@mtjade2007 I have another idea for you. If you don't want to use control strips, you can get yourself an X-Rite color target and take a photo of that target under controlled lighting. Matt's suggestion of using flash is a good one. Then, you can develop a roll at a well-known reputable lab. Now you have a reference. Scan it and save.

When you develop your own film, make the same exposure. When you scan your films, you can compare the RGB values of the grey patches of the target.

Essentially this very similar procedure to control strips but less precise, and it depends on using the same emulsion.

Click to expand...

I do have a Macbeth colorchecker chart. I tried it long time ago but it did not work for me. I found there were always some color patches that did not match the original while some others matched well. It could be because my processing was already bad and color crossover was causing the mismatch. I will continue to use the test setup as a reference standard. My Macbeth colorchecker is missing. I can not locate it any more. I will always take a shot of it to start with every roll of film. I can rearrange the setup to include better color combinations.

mtjade2007 said:

I do have a Macbeth colorchecker chart. I tried it long time ago but it did not work for me. I found there were always some color patches that did not match the original while some others matched well. It could be because my processing was already bad and color crossover was causing the mismatch. I will continue to use the test setup as a reference standard. My Macbeth colorchecker is missing. I can not locate it any more. I will always take a shot of it to start with every roll of film. I can rearrange the setup to include better color combinations.

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You could concentrate on the gray patches of the colour checker and let the rest fall where they may. I have been doing this for quite a while and has certainly improved the quality of my scans. After inversion, try making a set of curves that will give a neutral grayscale from all the gray patches and save it. Apply it to all the shots of this roll. I suppose you should have three parallel lines, but I never succeeded in it. Perhaps my primitive development gear is to blame. Anyway, the weirder the curve shapes, the more you have gone wrong I suppose...

mtjade2007 said:

C-41 process looks really simple but it is really very complicated considering all causes that could lead to a failure.

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C41 process is very simple, provided the guidelines are followed. That basically means strict temperature control for developer 38C (you can get away with a slight variation) and use fresh chemicals to develop fresh film.

You won't be able to see "out of tolerance" control strips with your eye but you can see "out of control".
Have a look here and I hope it helps.
https://www.olympus-lifescience.com...e/primer/photomicrography/colornegprocerrors/

Anon Ymous said:

You could concentrate on the gray patches of the colour checker and let the rest fall where they may. I have been doing this for quite a while and has certainly improved the quality of my scans. After inversion, try making a set of curves that will give a neutral grayscale from all the gray patches and save it. Apply it to all the shots of this roll. I suppose you should have three parallel lines, but I never succeeded in it. Perhaps my primitive development gear is to blame. Anyway, the weirder the curve shapes, the more you have gone wrong I suppose...

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Good point. I will dig out my colorchecker and try it again. Last time I did it it was under the sun light. I have a studio strobe now.

foc said:

C41 process is very simple, provided the guidelines are followed. That basically means strict temperature control for developer 38C (you can get away with a slight variation) and use fresh chemicals to develop fresh film.

You won't be able to see "out of tolerance" control strips with your eye but you can see "out of control".
Have a look here and I hope it helps.
https://www.olympus-lifescience.com...e/primer/photomicrography/colornegprocerrors/

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Thanks for the suggestion. It's a long article. I'll try to read it.

mtjade2007 said:

Yes, this will clearly tell if everything is in spec.

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It won't help you determine if your expired film is usable, though. Running control strips on one type of film may say something about the processing, but it won't guarantee that expired film run through that process will give good results. But I remain with the position that it's the end result that counts. If you get there using expired film and old chemistry, what gives?

mtjade2007 said:

Here is an image out of my scanner without any adjustment done to the scanner.

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That doesn't say much. What you need from the scanner is usable image information, but I wouldn't strive for a finished result straight from the scanner (and its software). Some adjustments to color will be necessary. It used to be like that when everything was optically printed just as well. With color negative film, there's simply no absolute benchmark. You get something with color information and then process and adjust to get the closest to your vision as possible. This vision may be an exact reproduction of real world colors or some artistic interpretation. In either case, the match with your expectation (assuming it's explicit to begin with) and the final print may be close, but will generally never be 100%. It just needs to be close enough for you to be happy.

mtjade2007 said:

Thanks for the suggestion. It's a long article. I'll try to read it.

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Yes it covers a lot but in fairly easy-to-read language.What puzzled me slightly was the statement that you have to avoid over agitation in the sense that the agitation of a Jobo rotary processor is a continuous and pretty fast so made me wonder what ways anybody would consider agitating by hand and in so doing would over agitate?

I suppose shaking the tank like a cocktail shaker might achieve this but for 3 mins 15 secs and anyway who would naturally attempt this?

pentaxuser

koraks said:

It won't help you determine if your expired film is usable, though. Running control strips on one type of film may say something about the processing, but it won't guarantee that expired film run through that process will give good results. But I remain with the position that it's the end result that counts. If you get there using expired film and old chemistry, what gives?

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Why not? Commercial labs frequently runs a control strip through the processor to determine if everything is in spec for the following processing of films from the customers. If a film comes out bad next the film can be determined to be bad, expired or else. If a good final image from an expired film after some adjustment comes out good why not call that film usable? Why a control strip run is not helpful?

koraks said:

That doesn't say much. What you need from the scanner is usable image information, but I wouldn't strive for a finished result straight from the scanner (and its software). Some adjustments to color will be necessary. It used to be like that when everything was optically printed just as well. With color negative film, there's simply no absolute benchmark. You get something with color information and then process and adjust to get the closest to your vision as possible. This vision may be an exact reproduction of real world colors or some artistic interpretation. In either case, the match with your expectation (assuming it's explicit to begin with) and the final print may be close, but will generally never be 100%. It just needs to be close enough for you to be happy.

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Are you saying the image straight out of the scanner contains no usable image information? I think some color adjustments will always be necessary regardless you print optically (tweaking dichroic filters) or print (sort of) to a digital file (photoshoping). You get the image information from the negative when you print optically. You get the info from the image straight out of the scanner when you print digitally. I can agree the two aspects of the image information may be different. But as you said the final image counts. If both (optical and digital) images after post processing match the expectation why the scanner image does not contain usable image information to begin with? Am I mistaken what you are saying?
.

pentaxuser said:

Yes it covers a lot but in fairly easy-to-read language.What puzzled me slightly was the statement that you have to avoid over agitation in the sense that the agitation of a Jobo rotary processor is a continuous and pretty fast so made me wonder what ways anybody would consider agitating by hand and in so doing would over agitate?

I suppose shaking the tank like a cocktail shaker might achieve this but for 3 mins 15 secs and anyway who would naturally attempt this?

pentaxuser

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I did experience an over agitation consequence by my JOBO ATL-2300. The developer is probably more oxidized after one use. I can reuse it one more time. I can process 4 220 rolls with one liter of the developer and will toss the developer after that. That's not really bad. It almost equals to 8 rolls of 135X36 films.

mtjade2007 said:

I did experience an over agitation consequence by my JOBO ATL-2300. The developer is probably more oxidized after one use. I can reuse it one more time. I can process 4 220 rolls with one liter of the developer and will toss the developer after that. That's not really bad. It almost equals to 8 rolls of 135X36 films.

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Can you say what happened differently to result in an over agitation? Presumably those processing figures that you then mention are what you can normally process when there is no over agitation?

Thanks

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. The used once developer will not keep long. The immediate reuse (one time) seems OK. Other than this, I don't feel any ill effect from the constant agitation. I believe it will probably boost contrast to the film which is not a bad thing at all. I tried to agitate at lower RPM (50 RPM instead of 75) I saw no difference still.

mtjade2007 said:

If a good final image from an expired film after some adjustment comes out good why not call that film usable?

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That's fine, of course. 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. In my mind, you might as well just use decent chemistry and follow instructions closely, and then just hope for the best.

I've printed from a lot of expired color film over the years. In literally all cases, the colors were compromised. In many cases, the output was presentable. In many other cases, it was a totally hopeless affair. In none of the cases, control strips and densitometry would have helped. It would have just been a waste of time and money on an inherently compromised workflow.

mtjade2007 said:

Are you saying the image straight out of the scanner contains no usable image information?

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No, I'm saying the same as you are: that there will always need to be color corrections/adjustments to the scanner output.

mtjade2007 said:

Am I mistaken what you are saying?

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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.