Do you test your film for true ISO?

Reading "The Art of Photography" and "The Negative" lately, and I'm curious how many of you actually go through the process to find the true ISO of your favorite film with your camera(s) and process(es)? If so, what procedure do you use to test for actual speed? I found this article online offering a plausible process: http://www.halfhill.com/speed1.html

I used to do it regularly when I had a working densitometer, using the method described in The Negative. What that taught me was what a good neg should look like. The genius of Adams' approach, I think, is that he figured out a way to teach people how to make good negs in a way that one could learn from a book, as long as you had a densitometer to read the negs. You didn't need to have an experienced teacher who could show you how to develop by inspection or who could look at your processed negs and tell you what you were doing wrong.

Having done that for a number of years, I can look at my negs with a new film and say "there's not enough shadow detail there, maybe I should rate that film a half stop slower," or I can look at my prints and say, "the highlights aren't brilliant enough when the shadows look right, maybe I should increase development time by 15%," and that's good enough.

I always shoot box speed. I cannot remember a time when I pushed film. My light meters work and I know how to correctly use them so I do not have to play the divide by two game.

I do set the light meter to read an area then set that area in the Zone the I want the print to be.

yes, I have tested my personal ISO for agfa aviphot, and developing times for what I need from the developer that I am using. In terms of the procedure, its very similar to all the other procedures>

I am doing my first test using this method: http://www.zone2tone.co.uk/zone-system-film-testing.htm

It is somewhat similar to the method in the link in your OP.

Sometimes...

I have in the past, but not currently. My constraint is not equipment. I have a nice densitometer purchased new by me years ago. My constraint is time and weather. Time due to job responsibilities. And weather because clear sunny skies are my uniform light source of choice for the test exposures, and the Pacific Northwest doesn't have many of those over the course of a year to begin with. Especially on Saturdays and Sundays.

These days I simply use box speeds and recommended development times. Fine tuning will need to wait until retirement in a few years. The procedure is not difficult. And as David says, one can learn a lot by doing it.

I can't even imagine what waking up each morning and doing what I want to do will be like. That hasn't happened on a long-term basis since I was 4-years-old.

Ken

Film testing is a ghost of the part. I find such tests a waste of time and money. Companies like Kodak and Ilford test each batch of film to determine if they meet their standards. Why duplicate their work.

Michael R 1974 said:

So to answer your question, you can easily avoid the testing procedure for a Zone System EI. Just downrate your film by 1 stop (rounded for simplicity) and that's all there is to it. That's what you'll end up with even after going through the test procedure.

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And this matches exactly with my own findings. My EI for ISO400 b&w films almost invariably came to EI250 in the Zone System. My negatives were thus just a little bit more dense overall.

One practical reason now for me using box ISO400 is that my enlarger head is an Aristo VCL4500 variable contrast system with the dual blue/green additive fluorescent grid tubes. My tubes are a new replacement set from LCD Lighting (the Louise Kessler deal), and they are a notch dimmer than the original tubes, which were never bright to begin with.

This means that less dense negatives, especially 35mm negatives where most of the diffused light is not transmitted through the tiny negative carrier opening to begin with, provide shorter and thus more workable printing times. There are no adjustable condensers in a cold light head.

Ken

No. If it is Kodak or Ilford film I assume they checked the batch before sending it out.

Gerald C Koch said:

Film testing is a ghost of the part. I find such tests a waste of time and money. Companies like Kodak and Ilford test each batch of film to determine if they meet their standards. Why duplicate their work.

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One reason might be that all of the other links in the chain of processing as performed by me in my personal darkroom are likely far different than Kodak's and Ilford's standardized test regimens.

The personalized tests are supposed to individually calibrate the entire process for each different film, not just the exposure part. It's my overall standards that are being defined, not theirs.

Ken

Gerald C Koch said:

Film testing is a ghost of the part. I find such tests a waste of time and money. Companies like Kodak and Ilford test each batch of film to determine if they meet their standards. Why duplicate their work.

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The technical term that you are referring to is WOMBAT1















1WOMBAT ==> Waste Of Money Brains And Time

Ken Nadvornick said:

The personalized tests are supposed to individually calibrate the entire process for each different film, not just the exposure part. It's my overall standards that are being defined, not theirs.

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This is more of an urban legend than fact. If you think about it, you'll have to test every shutter speed and f/stop combination of every lens. What you want to do is reduce the variables. If you want to test the film speed, eliminate as many variables as possible that can obscure the results, then test for film speed. If you want to know about the lenses, then have them calibrated separately. Michael had a good explanation of how the concept of "true" film speed is also wrong thinking.

Don't forget that shutter speed can change with ambient temperature so you need to test for that too.

Stephen Benskin said:

This is more of an urban legend than fact...

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One must always be careful not to allow the perfect to become the enemy of the good. That includes perfect negatives as well as perfect positives.

It's neither practical nor desirable to standardize (or normalize) every possible variable in the film processing chain. That would be far beyond the sweet spot needed to produce meaningful work. However, that also does not mean one should ignore everything, because to undershoot the sweet spot would be equally questionable.

The idea in practical testing is to try to calibrate the big things that may have the greatest effect, while ignoring the smaller things whose aggregate effects may be relatively trivial by comparison.

So for example, worrying about the chemical quality of one's processing water supply is, in most cases, overkill. But worrying about keeping the temperature of that processing water standardized to within a couple of degrees of a working set point is not.

Best to just pick a single shutter for testing that's reasonably close and stick with it, settle on an agitation regimen that's easily accomplished and remembered, pick a convenient processing temperature and a repeatable thermometer, pick a couple of general purpose films that are readily available, choose a standard developer and dilution, use the same graduate to measure concentrates, and fix all of the other potentially large error contributors.

Then just run some tests under one's normal working conditions, and be done with it. No need to go nuts. We have enough of those around here already. And no need to ignore everything. We also have our share of those. Both are standing outside of the practical sweet spot, and their results often confirm that.

Ken

Ken Nadvornick said:

One must always be careful not to allow the perfect to become the enemy of the good. That includes perfect negatives as well as perfect positives.

It's neither practical nor desirable to standardize (or normalize) every possible variable in the film processing chain. That would be far beyond the sweet spot needed to produce meaningful work. However, that also does not mean one should ignore everything, because to undershoot the sweet spot would be equally questionable.

The idea in practical testing is to try to calibrate the big things that may have the greatest effect, while ignoring the smaller things whose aggregate effects may be relatively trivial by comparison.

So for example, worrying about the chemical quality of one's processing water supply is, in most cases, overkill. But worrying about keeping the temperature of that processing water standardized to within a couple of degrees of a working set point is not.

Best to just pick a single shutter for testing that's reasonably close and stick with it, settle on an agitation regimen that's easily accomplished and remembered, pick a convenient processing temperature and a repeatable thermometer, pick a couple of general purpose films that are readily available, choose a standard developer and dilution, use the same graduate to measure concentrates, and fix all of the other potentially large error contributors.

Then just run some tests under one's normal working conditions, and be done with it. No need to go nuts. We have enough of those around here already. And no need to ignore everything. We also have our share of those. Both are standing outside of the practical sweet spot, and their results often confirm that.

Ken

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It's more about whether it's worth testing if the test results are questionable. Zone System testing results in a consistent difference from the ISO speed because it has a different methodology. It's really not worth testing when using a general developer. The difference is in the actual test and not the materials. Something not many people seem to be concerned about. I'm saying this not because I don't believe in testing. I have a calibrated sensitometer and have written plotting and tone reproduction programs. I'm saying that the quality of the results most people obtain isn't worth the effort.

I agree that it's more important to be consistent and conscientious with processing. This is what people need to focus on. If someone has the need to test, test how the film responds to development.

I don't just test for EI but for the old "shadow detail/ highlight" parameters. I want good shadow detail and I want my highlights to be where I want them to be. I test using basic zone system procedures (without going nuts over it) and I find really helpful. It eliminates a lot of guesswork, it makes negatives a lot easier to print, and it means less dancing around in the darkroom.

It is different if you are using roll film but you can still do some very quick tests to eliminate some of the guess work.

I put my film in the camera . . . if it fits, it passes the test.

Ken Nadvornick said:

One must always be careful not to allow the perfect to become the enemy of the good. That includes perfect negatives as well as perfect positives.

It's neither practical nor desirable to standardize (or normalize) every possible variable in the film processing chain. That would be far beyond the sweet spot needed to produce meaningful work. However, that also does not mean one should ignore everything, because to undershoot the sweet spot would be equally questionable.

Click to expand...

Well, one needs to evaluate, for their own operation, how far to go.

I come from a background of high volume processing, and many things that you probably think are major overkill, we did. In our main lab, we wouldn't let a new batch of developer replenisher go into use until we had screened it, including actual processing of a test strip. I can't think of a significant variable that we did not at least consider.

There used to be occasional posts here as to what is a "photograde" chemical? I had posted that it had to meet (then)ANSI standards fo photograde. But the silly comments would continue, like "I think food grade is a higher standard, so it should meet photograde standards." I'm too polite to tell them they're idiots, but they are. We had dozens of ANSI standards for chemicals, and would not consider using (hardly) anything until we had prescreened it per what we considered the key requirements - typically the assay and any crucial contaminants.

Anyway, my point is that not every apug user has the same needs that you do, so keep an open mind.

The reason that I turned against testing was back when HIE was discontinued, I only had one 36 exposure HIE roll. I said that I was going to set the camera light meter to ISO 400 [the box speed], attach the red filter and use the setting that the light meter gave me. I promptly was taken to task on APUG by several self appointed self taught experts that I should set up the camera on a tripod for one scene and shoot every combination of f/stop and shutter speed for the full roll of film. That way I would really know what the film could do. Of course those $#!+ for brains self appointed self taught experts were unable to fathom that I would then know everything about HIE but would not have any HIE to shoot. I shot box speed with the red filter and metered through the lens. All the photographs came out. So much for those self appointed self taught test-every-film-with-every-possible-developer-for-every-possible-lighting-for-every-phase-of-the-Moon-in-every-season-for-every-decade-in-every-century experts.

The result has been that I am strongly test adversive and I would only derate the film speed to get a slightly denser negative. So far I have not needed a denser than normal negative, however there are some alternative printing methods that require denser negatives.

The best test is to shoot a roll/sheet using the manufacturer's recommendation, and then develop the roll/sheet using the manufacturer's recommendation.

Try to use a nice, representative scene or set of scenes, and a couple of different lighting conditions.

And then look at, and print, the results.

If the results are consistently wrong, that will tell you a lot about your technique and equipment. You can adjust the EI you use to correct.

If the results are inconsistently wrong, then you need to delve deeper into the condition of your equipment and/or technique, because a change in the EI you use isn't going to help.

The interesting wrinkle to all of the above?

No where does it say anything about testing the film. It is the other stuff that gets tested.

ic-racer said:

No. If it is Kodak or Ilford film I assume they checked the batch before sending it out.

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This is all you need to know.

Yes I do. Not because I don't believe the box. I do it because I know so little and by working through every possible scenario, I gain some knowledge. So I'm not really trying to calibrate my development procedure or determine my personal EI. I'm trying to calibrate my brain to the procedure by experiencing all of the variables first hand.

Gerald C Koch said:

Film testing is a ghost of the part. I find such tests a waste of time and money. Companies like Kodak and Ilford test each batch of film to determine if they meet their standards. Why duplicate their work.

Click to expand...

Ken Nadvornick said:

One reason might be that all of the other links in the chain of processing as performed by me in my personal darkroom are likely far different than Kodak's and Ilford's standardized test regimens.

The personalized tests are supposed to individually calibrate the entire process for each different film, not just the exposure part. It's my overall standards that are being defined, not theirs.

Click to expand...

MattKing said:

The interesting wrinkle to all of the above?

No where does it say anything about testing the film. It is the other stuff that gets tested.

[Emphasis by Ken.]

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Well, this is the point (above) that I was originally trying to make in response to Gerald.

That while it's true that Kodak and Ilford have rigorously tested their films for ISO speeds, and as Michael noted a Zone System test will almost always result in about 2/3-stop less than the ISO speed (and my past tests confirmed that in my own case), there still might be other reasons to perform a personal set of tests.

One of those reasons being that Kodak and Ilford did not perform their speed calibration and development time tests in my darkroom, using my thermometers, graduates, agitation protocols, and everything else. And while it's true that speed points are far less susceptible to these variables, what I am really trying to standardize by (brief, but careful) testing is my development times. And those times are very susceptible to all of the variables and vagaries of my own darkroom processing procedures.

I'm confident that if I want St. Ansel's Zone System shadow detail I really don't need to waste the time and energy finding it on my own. Just rate my ISO400 b&w film at about EI250 and I'm essentially there, barring malfunctioning equipment.

But my graduates are likely not the same as your graduates. Or Kodak's and Ilford's. And if they vary by, say, 10%, and I use them to measure concentrated developers prior to dilution, then yeah... my own personal development times might vary drastically from Kodak's and Ilford's recommendations.

Now it's also true that with today's modern variable contrast papers the bulls-eye on the development time target may be significantly larger than it was in St. Ansel's day. But in my case I may also wish to calibrate my development times to help out my Aristo VC enlarger light source.

It's wonderfully precise and flexible when it comes to varying contrast. I have step-wedge calibrated it down to 1/4-grade increments with the whole grades hitting the exact mid-points of the ISO contrast grade specs, additionally supplied with a set of exposure threshold-based conversion factors available for changing exposure times between any two fractional grade settings for added convenience.

But the price I pay for this precision is pretty dim blue and green tubes. So I need thinner negatives for manageable printing times. And since my own testing also showed that the blue tube is roughly 10 times faster than the green tube, too much negative contrast means having to print softer (greener), which in turn means much longer exposure times as well. And I try to mitigate these problems at the negative processing stage as best I can.

So yes, there may indeed be other reasons to perform overall film testing beyond simply repeating Kodak's and Ilford's speed tests. That's all I was saying.

Ken

I have to do it because I´m using Perceptol and you never know which speed you´ll get. However, I use no scientific method. I just bracket a few shots on 120, develop and make a contact sheet on grade 3 Galerie with the minimum time for maximum black. Then I choose the one where the shadows look right.

I ran Zone system tests on the Agfa & Kodak films I used back in the late 1980's. However when I switched to Ilford films I took Matt King's approach mainly because I was away from home in Chile/Peru and couldn't get more Tmax film, I'd been using Ilford films a decade earlier so had every confidence in them.

The last films I tested for personal EI were Fomapan 100 & 200, that really was necessary as they need careful handling to tame the contrast and shadow details, I also tested for reciprocity failure which I found was nothing like as bad as Foma's recommendations in the situations I'd typically shoot in.

Some sort of testing is valuable, what you're really doing is building up experience of a film and the process and how best you handle exposure and development to ensure you get the best possible results.

Ian