C-41 lab processing - is there much variation?

runswithsizzers · Jul 4, 2021

Is finding a "good" lab - and avoiding "bad" labs - a major consideration for C-41 processing?
(I am asking about the processing, only, because I already know there is a big variation in lab scans, and I don't usually get prints with processing.)

My local camera store has an in-house lab that is convenient, fast and affordable. What I don't know is if I can trust their processing. They use a Fuji mini-lab which is, by their own admission "30-years old." The same staff has been running this equipment for a long time, so they have experience - but does experience always translate to reliable results?

For me, the problem is:
How do I evaluate the quality of C-41 processing? If the negatives are scratched or dirty - I can easily see that. But how do I evaluate color accuracy and longevity?

So, I am trying to decide if it would be worth the extra hassle of sending my C-41 film to another lab.

Can anyone say if most mini-labs produce about the same quality of results - or are there a significant number of mini-labs producing C-41 results with significant color variation and / or negatives that are more likely to fade or shift colors with time?

cramej · Jul 4, 2021

If the same staff has been running the lab for 30 years, that's a good sign. There's no problem with 30 year old equipment if they maintain it right. Those machines don't last if they're not maintained. The million dollar question is 'how much do they process? '. If they only have enough volume to run it once a week, then the chemicals probably aren't that great and the quality will be poor.

BrianShaw · Jul 4, 2021

For me there are two ways to determine if a lab is good or not: reputation and my personal experience. Turnaround time is also considered. Price is not much of a factor. The best option is really for you to give them a try… whoever “them” may be. Why not shoot and process a roll at your local place first?

runswithsizzers · Jul 4, 2021

cramej said:
If the same staff has been running the lab for 30 years, that's a good sign. There's no problem with 30 year old equipment if they maintain it right. Those machines don't last if they're not maintained. The million dollar question is 'how much do they process? '. If they only have enough volume to run it once a week, then the chemicals probably aren't that great and the quality will be poor.

I am always offered the option to pick up my negatives later the same day, so the machine seems to be in constant use, rather than running periodic batches. I don't really know what kind of volume they do. I live in a city of about 150,000 population. There is only this one camera store, but of course there are also Wal-Marts, Walgreens, ect. where people can drop off negatives for processing.

When you say "...the quality will be poor" - one of my questions is, What does poor quality look like?

MattKing · Jul 4, 2021

Ask them if they use control strips and keep their process within specifications. If they say yes, that is a very good sign.
Are the negatives clean and sleeved when you get them back? If so, that is another very good sign.
If you have a standard C-41 film that you use within date, does the appearance of the negatives (mask colour, density of edge printing and highlights) seem consistent from roll to roll? If so, that is a good sign.
For more than that, you need to get much more technical.

Mr Bill · Jul 4, 2021

runswithsizzers said:
When you say "...the quality will be poor" - one of my questions is, What does poor quality look like?

The only thing that you, as someone inexperienced in these things, would likely to be able to notice is badly handled film, that is, dirty or scratched.

With respect to the proper degree of development, the only direct way to evaluate this is by the use of something known as a "process control strip." These are supplied by a material manufacturer. They consist of a set of test strips precisely exposed by the manufacturer, along with one already processed strip. The processed strip was run through a "correct" process, and serves as an ideal reference. So the lab will periodically process a test strip of their own, then compare the result vs the reference. Both are read via a densitometer, then the differences are compared vs the acceptable tolerances per the manufacturer. Some of the things compared are a low-density vs a high-density patch, where the individual dye layers are compared (the color densitometer can separate these out of a single test patch). These show the overall degree of development as well as the contrast of each dye layer. Additionally the control strip has special patches to evaluate how well the bleach and fix are performing. But... the control strip won't be able check for adequate wash. So this would depend on the lab running the correct replenishment rates.

I think that what I'd do to evaluate a lab is to first watch how they handle film; if they carry it around, letting the end brush against tables or desks, that's a bad sign. This is where individual techs may differ widely. Next I'd ask someone aboug their "process control," such as how tight is it? I'd personally like to see the plots, but presumably you have no idea what to look for, so the best you can do is to ask the tech to give you a quick explanation. Then you judge based on how it sounds. Ask a few questions to see how they respond. If they try to talk over your head, this is generally a sign that they may be blowing smoke. So tell them it's over your head, and people who know what they're doing can generally change the level of their explanation. Some questions you might ask are, how do they set their wash water rate, or how do they know if their fixer is ok, etc. Again, you judge based on whether they have a seemingly legitimate answer, etc. Probably not much else you cago by.

FWIW I'm going by formal quality specs that may not be that important anymore. Scanned images can take care of a lot of problems that would have been an issue, in the past, with optical printing.

Ps, a failure to give good explanations about "process control" doesn't necessarily mean poor quality. All it takes is for one qualified person to be overseeing this, and it's ok. You could have a half-dozen people running the machine who know nothing about process control, but it's ok because the one person has got things in hand. So that one person is the one you want to explain it to you. You might also ask them what happens if something goes wrong while they are not working.

runswithsizzers · Jul 4, 2021

BrianShaw said:
For me there are two ways to determine if a lab is good or not: reputation and my personal experience. Turnaround time is also considered. Price is not much of a factor. The best option is really for you to give them a try… whoever “them” may be. Why not shoot and process a roll at your local place first?

I have had them process at least half-a-dozen rolls in the past year or two. Two of those were out-dated film from my freezer, and may have slighty underexposed - so they were not reliable benchmarks. With fresh film, the 4x6 lab prints look fine. But if I understand correctly, these old Fuji Frontiers are pretty good at making OK prints even from sub-optimal negatives - yes? no? All of the lab-scans from my local lab, and also from Dwayne’s Photo in Parson's Kansas looked bad with excess grain / noise in the shadows.

Which highlights my problem - if I can't trust the prints because they may be hiding small errors in processing - and I can't trust the scans because they introduce a whole 'nother can of worms - then how do I tell if the processing is reliably producing accurate color?

BrianShaw · Jul 4, 2021

If you like the prints then all is okay. Don’t overanalyse things too much. What impact is associated with “small errors in processing”?

And, yes, if the right buttons are pushed the Fuji Frontier will attempt to make your prints look as good as they can. Whether that’s what you want is a different story.

If there is noise in the dark areas, I’d suspect incorrect exposure is the problem rather than bad processing. But base your assessment on the the primary product - negs - rather than scans.

If color accuracy is an issue, photograph a calibrated color gizmo.

runswithsizzers · Jul 4, 2021

MattKing said:
Ask them if they use control strips and keep their process within specifications. If they say yes, that is a very good sign.
Are the negatives clean and sleeved when you get them back? If so, that is another very good sign.
If you have a standard C-41 film that you use within date, does the appearance of the negatives (mask colour, density of edge printing and highlights) seem consistent from roll to roll? If so, that is a good sign.
For more than that, you need to get much more technical.

Previously, my negatives came back from this lab in translucent plastic sleeves. But as discussed <here> - the last roll I got back was just bare negatives loose in a paper envelope. Now that I think about it, I asked them to cut the recent roll to 5 frames, and their plastic sleeves are made to hold 4 frames each. I have not noticed any problems with dust or scratches.

I will ask about the test strips next visit. But. Previously, when I've asked questions about various topics, the senior lab operator tends to get defensive for some reason. Communication has not been that good.

With one or two exceptions, the employees of this store do not have a reputation for being particularly friendly. Maybe it's me - that old guy who never wants to buy a new digital camera, but just wants a roll of film and then complains because it's six months out-of-date.

MattKing · Jul 4, 2021

runswithsizzers said:
I will ask about the test strips next visit. But. Previously, when I've asked questions about various topics, the senior lab operator tends to get defensive for some reason. Communication has not been that good.

Start by telling them you are trying to teach yourself about how this stuff works, and that you have seen some material about process control strips but don't understand what those are. Ask them if they use them, and can they explain them to you.
The "eager student" approach is a great way to butter up lab techs.

BrianShaw · Jul 4, 2021

… or better yet, rather than asking for detailed technical information that you don’t know how to interpret to “qualify them”… just tell them that you’d appreciate better handling of your negs and ask if delivering them in sleeved is now the norm and if so you’ll take your business elsewhere.

In my highly specialized engineering discipline I was periodically assaulted by management nit-picking when it was perfectly clear that even the question they asked was either not well informed or was completely ignorant and they were going to direct an engineering decision based on what they thought sounded good rather than what was more correct. I would have rather Ed then just say “cut 20% from the budget and there is no discussion “ than pretend to be doing a deep-dive when they didn’t really even understand their own questions.

Tell the lab what your requirements and expectations are… let them run their business. If they want you as a customer they will deliver what you expect. But asking them to “prove to you” that they know what they are doing is likely always a way to make an enemy.

unless you are a VERY BIG AND PROFITABLE. customer.

MattKing · Jul 4, 2021

Brian is correct if you are dealing with a high volume lab.
Dealing with a small, local lab may require a more individual and personal approach, because anyone who has managed to keep a small lab operating over these last years is probably at least a little bit of a character.
Consider reaching out to foc here on Photrio. He just retired and closed down his small local lab in Ireland after many years of operation. He probably has a good perspective on this.

runswithsizzers · Jul 4, 2021

Mr Bill said:
The only thing that you, as someone inexperienced in these things, would likely to be able to notice is badly handled film, that is, dirty or scratched.

With respect to the proper degree of development, the only direct way to evaluate this is by the use of something known as a "process control strip." These are supplied by a material manufacturer. They consist of a set of test strips precisely exposed by the manufacturer, along with one already processed strip. The processed strip was run through a "correct" process, and serves as an ideal reference. So the lab will periodically process a test strip of their own, then compare the result vs the reference. Both are read via a densitometer, then the differences are compared vs the acceptable tolerances per the manufacturer. Some of the things compared are a low-density vs a high-density patch, where the individual dye layers are compared (the color densitometer can separate these out of a single test patch). These show the overall degree of development as well as the contrast of each dye layer. Additionally the control strip has special patches to evaluate how well the bleach and fix are performing. But... the control strip won't be able check for adequate wash. So this would depend on the lab running the correct replenishment rates.

I think that what I'd do to evaluate a lab is to first watch how they handle film; if they carry it around, letting the end brush against tables or desks, that's a bad sign. This is where individual techs may differ widely. Next I'd ask someone aboug their "process control," such as how tight is it? I'd personally like to see the plots, but presumably you have no idea what to look for, so the best you can do is to ask the tech to give you a quick explanation. Then you judge based on how it sounds. Ask a few questions to see how they respond. If they try to talk over your head, this is generally a sign that they may be blowing smoke. So tell them it's over your head, and people who know what they're doing can generally change the level of their explanation. Some questions you might ask are, how do they set their wash water rate, or how do they know if their fixer is ok, etc. Again, you judge based on whether they have a seemingly legitimate answer, etc. Probably not much else you cago by.

FWIW I'm going by formal quality specs that may not be that important anymore. Scanned images can take care of a lot of problems that would have been an issue, in the past, with optical printing.

Ps, a failure to give good explanations about "process control" doesn't necessarily mean poor quality. All it takes is for one qualified person to be overseeing this, and it's ok. You could have a half-dozen people running the machine who know nothing about process control, but it's ok because the one person has got things in hand. So that one person is the one you want to explain it to you. You might also ask them what happens if something goes wrong while they are not working.

Thanks to you and @MattKing for explaining how the process control strips work! I was deeply involved with quality control in a hospital medical lab, so I understand QC basics, but not the specific process used by photo labs.

As mentioned in my reply to MattKing, communication is difficult with this lab. It's not that they talk over my head, but the guy in charge tends to get defensive - like I am accusing him of doing something wrong, or challenging him of not knowing his job. I know communication is a two way street, but I do try to follow the rules of good interpersonal communication. When talking to this person, I try to be very careful to avoid language that might be intrepreted as an accusation, but he seems to have a hair-trigger defense mechanism. I don't think there is much possibility of me asking a lot of QC questions without this this guy's blood pressure going way up. So, if I only get one question, would it be, "How often do you run process control strips?" - or something else?

I hesitate to mention it in this analog only forum, but I don't have a color darkroom, and I will be doing the color inversions myself on camera-copies of the negatives. Are you saying that negatives which may have moderate color shifts due to slight variations in C-41 processing are less significant in a hybrid workflow? (Or should I not ask that question here?) I posted in the Analog forum because my assumption was that I want good processing (RE: color accuracy) no matter whether the negatives are to be used in the darkroom or scanned - maybe that assumption is not valid?

MattKing · Jul 4, 2021

Moderate colour shifts are not a problem - whether you are printing in the darkroom, or using a hybrid approach.
Moderate colour crossover is a problem - whether you are printing in the darkroom, or using a hybrid approach.
Crossover is where the contrast behavior of the red, green and blue responsive emulsion components becomes unmatched. It shows itself with things like green highlights but magenta shadows (or vice versa) when the light levels change for a subject of consistent colour and tone. Such as someone's face, as the light transitions from the highlights on the cheeks, to the shadows under the jaw.
Fixing crossover in the printing darkroom is incredibly difficult - it requires more complexity than you want to worry about.
Fixing crossover in a hybrid approach is more doable, but you don't want to have to do it a lot.
Out of specification C-41 development tends to cause crossover problems.
However, if the lab is doing machine prints for people, they won't be happy if they are seeing crossover, because those negatives are much harder for them to scan and print. So the things that concern you, will most likely concern them.
I've known a couple of lab people like the one you are dealing with. If you get on his good side with an appropriate approach to geekiness, things may get better .

runswithsizzers · Jul 4, 2021

MattKing said:
Moderate colour shifts are not a problem - whether you are printing in the darkroom, or using a hybrid approach.
Moderate colour crossover is a problem - whether you are printing in the darkroom, or using a hybrid approach.
Crossover is where the contrast behavior of the red, green and blue responsive emulsion components becomes unmatched. It shows itself with things like green highlights but magenta shadows (or vice versa) when the light levels change for a subject of consistent colour and tone. Such as someone's face, as the light transitions from the highlights on the cheeks, to the shadows under the jaw.
Fixing crossover in the printing darkroom is incredibly difficult - it requires more complexity than you want to worry about.
Fixing crossover in a hybrid approach is more doable, but you don't want to have to do it a lot.
Out of specification C-41 development tends to cause crossover problems.
However, if the lab is doing machine prints for people, they won't be happy if they are seeing crossover, because those negatives are much harder for them to scan and print. So the things that concern you, will most likely concern them.
I've known a couple of lab people like the one you are dealing with. If you get on his good side with an appropriate approach to geekiness, things may get better .

Thank you for that information, very helpful!

Regrettably, before I switched to the lab, I worked retail, and was I probably one of those "people like that" myself. Not defensive, but maybe arrogant and not as sensitive to the customer's needs as I should have been. It's no excuse, but I was burn-out and I felt chronically under-compensated. We had one customer that always got the red-carpet treatment, though. He was very generous with gifts of liquor during the holidays - and top-shelf liquor, too - the good stuff we retail employees could not afford to buy. So I guess maybe I need to buy this shop a case of single malt Scotch.

BrianShaw · Jul 4, 2021

runswithsizzers said:
So I guess maybe I need to buy this shop a case of single malt Scotch.

Couldn't hurt... but ask first... he may be just as happy with a case of cheap beer.

runswithsizzers · Jul 4, 2021

BrianShaw said:
Couldn't hurt... but ask first... he may be just as happy with a case of cheap beer.

Good point! I think they need something, though. Sometimes everyone in that store acts like they just got out of meeting where the owner announced there will be no raises this year and no Christmas bonus, either.

Paul Howell · Jul 4, 2021

Getting one day service at a lab with a city of 150,000 is pretty good. Phoenix Metro has a population around 4.5 mil, 2 2 labs, both labs only run their C41 processor one or two days a week. If your scans seem ok, no really wacked color shifts or really thin negatives I would not give it to much thought. On the other hand, you want to make sure that the lab is running a control strip every day, last thing you want is to take in once in a life time shoot and find that your negatives are pooched. BTW, at lest here in Phoenix Walmart, Walgreens, and CVS send film out to lab in L.A, the negatives are scanned and the files are emailed back to the store for printing, negatives are not returned. Although I live about 2 miles from one of the labs and 5 miles from the others I also send film to Blue Moon, just in case any one of the labs close.

BrianShaw · Jul 4, 2021

negatives are not returned

That, for me is a deal breaker.

Adrian Bacon · Jul 4, 2021

MattKing said:
Ask them if they use control strips and keep their process within specifications. If they say yes, that is a very good sign.
Are the negatives clean and sleeved when you get them back? If so, that is another very good sign.
If you have a standard C-41 film that you use within date, does the appearance of the negatives (mask colour, density of edge printing and highlights) seem consistent from roll to roll? If so, that is a good sign.
For more than that, you need to get much more technical.

+1

If they use control strips, you should see very little variation with C-41. They should be able to readily answer that question, and tell you how frequently they run a control strip.

MattKing · Jul 4, 2021

Old Gregg said:
@MattKing I am on my second year of getting back to analog photography, so I am far from being an expert, but I'm beginning to suspect that the distinction between color crossover and color shift is not a thing. I have never seen, not once, the use of color crossover anywhere but on APUG. It is never mentioned in the Fuji C41 technical bulletin, or in the troubleshooting section of Kodak's Z-131 or in any other publications.

According to everything I've learned, due to a gross exposure or development error your contrast across CYM layers won't match the datasheet, and you get color that's different from the spec. "Crossover" or "shift" that's just a jargon difference, not a technical one. Basically, it's the analog version of channel clipping.

Don't mind being wrong on this one, just sharing what I have learned.

Here is a good LFPF thread on the subject, complete with some familiar participants:
https://www.largeformatphotography.info/forum/showthread.php?157789-Color-Crossover&p=1547936
Mick Fagan's post is particularly useful.
And the curves do cross, when the processing is way out of spec.

MattKing · Jul 4, 2021

And for clarity, I have had to (optically) print C-41 negatives that suffered from crossover due to poor development.
Yech!
In the lab we worked in, we ended up refusing work from one professional photographer who tried to save money by using his own processor (a Wing Lynch, IIRC) rather than having it done by one of the good labs in town.

MattKing · Jul 4, 2021

Old Gregg said:
@MattKing yep, that's a great thread - I saw it earlier and that's what I was referring to above (mismatched channel gamma). This is covered in Z-131 (troubleshooting and reading control strips) and easy to understand just extrapolating from B&W development. But how do you get a color shift then? Intuitively a "shift" feels like a linear adjustment, i.e. one of the channels/film layers just becomes uniformly less/more sensitive. How's that even possible?

When the contrast behavior of the three different colour emulsion components isn't matched, a change in light level at the film will result in different changes in each of those components.
A shadow may shift to magenta, because the response of the blue and red components to the change is low, while the response of the green component to the change is high.
Then, when the light increases to high mid-tone, the response of the blue and red components may increase, while the response of the green component increases less, resulting in a shift to green in the high mid-tones.
And of course, with three different colour components, and three different, potentially non linear contrast responses, you can end up with different shifts for every light level recorded - a kaleidoscope of non dependable colour responses.
The entire purpose behind the design of both the process and the film is to make those three components respond consistently and in lock step to changes in illumination - in other words parallel curves that don't "cross over" each other.

Adrian Bacon · Jul 5, 2021

MattKing said:
When the contrast behavior of the three different colour emulsion components isn't matched, a change in light level at the film will result in different changes in each of those components.
A shadow may shift to magenta, because the response of the blue and red components to the change is low, while the response of the green component to the change is high.
Then, when the light increases to high mid-tone, the response of the blue and red components may increase, while the response of the green component increases less, resulting in a shift to green in the high mid-tones.
And of course, with three different colour components, and three different, potentially non linear contrast responses, you can end up with different shifts for every light level recorded - a kaleidoscope of non dependable colour responses.
The entire purpose behind the design of both the process and the film is to make those three components respond consistently and in lock step to changes in illumination - in other words parallel curves that don't "cross over" each other.

hrmmm… even when it’s in process, they’re not parallel. Each color channel has its own gamma. In my experience, when people refer to “crossover” or the “curves got crossed” that just means the gamma of each color isn’t what it’s expected to be relative to what RA-4 would need to actually produce the colors it should.

in analog land, that’s kind of a problem as RA-4 paper is not infinitely malleable. In hybrid land, it’s a lot less of a problem, though many people don’t understand what is actually happening well enough to really effectively fix it when combined with a lack of knowledge of the hybrid tooling available to them. This is largely why some members here are very outspoken against the ability of hybrid being able to fix it. They haven’t seen many people fix it well and don’t seem to be aware of (or willing to be aware of) what modern digital tooling can do.

in short, an out of control process is a problem if you’re going to print optically. If you’re going to scan it, as long as you know what is actually happening, it’s not so much of a problem.

foc · Jul 5, 2021

The OP has got some very good advice already.
Control strips are a must for any lab.
I would also think of how the minilab looks, is it neat and tidy.
If you can see processing machines, do they have stains on the side (bad sign) or are they clean looking (good sign). If house keeping is poor, you can bet the processing is too.
How is their attitude to film customers? Welcoming?
And most importantly, if anything goes wrong, blame the lab (that's a joke by the way)

C-41 lab processing - is there much variation?

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