Do you test your film for true ISO?

Ken Nadvornick · Sep 25, 2015

Gerald C Koch said:
A clear distinction must be made between testing a film and test ones method. The OP was concerned with testing a film. Testing one's method is really the converse of testing a film. For testing one's method a constant known quantity is needed and this is a particular film's known ISO or box speed. The two tests are very different in their intent.

Stephen Benskin said:
+1

While acknowledging that this is legitimate, it's also important to acknowledge the context of its legitimacy.

What is being described is the distinction between using test procedures to test film, and using film to test the test procedures. Which then logically begs the hypothetical question of who or what is testing and certifying the tests of the test procedures. And who then is certifying the tests of the tests of the test procedures...

I'll wager that the majority reading this probably consider such distinctions to be well beyond the sweet spot I described earlier. The definition of which is the one step back from the starting point of diminishing returns.

Our home darkrooms are not the Kodak Research Laboratories. Many of us simply want to reasonably isolate the biggest sources of error, correct them sufficiently to allow us to obtain a reasonable level of overall system consistency, and then get on with the real goal of making photographs.

There will always be those who strive for absolute repeatable perfection above all else, including that same sweet spot good. And conversely those who choose, or in some cases are forced by default, to rely wholly on randomness and chaos and hope for something acceptable to happen.

Photography is a very big tent.

Ken

Stephen Benskin · Sep 25, 2015

handle2001 said:
So acknowledging the difference between ISO and EI, what methods do you use to determine your personally preferred EI? I'm not looking to spend the rest of my life as a sensitometrist, I just want to find out how to make the best possible pictures with my film/camera/developer combo that will also give me negatives that aren't difficult to print from. I can see the point about Ansel's methods being Ansel's and being only one way to skin a cat, etc., but that's why I post these questions because I am just stepping into this world from "enthusiastic snapshooter" land.

The most important part is determining the processing time. I suggest buying a step tablet. Finding the right contrast is what will make the negative print easier. Your EI will come from shooting and what works best for you.

Thomas Bertilsson · Sep 25, 2015

Yes, I do.

But since I only use two b&w films, I don't really have to worry about it either. Were I forced to change films, it'd be simple to do again.
I should mention I don't use a highly scientific method. I just bracket exposures in varying lighting scenarios, develop normal, and contact print to check shadow detail.
Then I adjust developing time to get correct contrast. Done.

dpurdy · Sep 25, 2015

Awfully easy thing to do, especially since I use a spot meter and have a densitometer. If I have a couple of frames left at the end of a roll I will invariably go to my favorite wall outside and shoot a Z1 and Z7. Not so much to test the film but to see that my whole process is where I thought. If it comes out off then I have several variables to look at to find out what happened.

Ken Nadvornick · Sep 25, 2015

dpurdy said:
Awfully easy thing to do, especially since I use a spot meter and have a densitometer. If I have a couple of frames left at the end of a roll I will invariably go to my favorite wall outside and shoot a Z1 and Z7. Not so much to test the film but to see that my whole process is where I thought. If it comes out off then I have several variables to look at to find out what happened.

I do the same. It's the main ongoing use of my densitometer.

The only few additional variables I will try to control is to use a black (or darker) wall for the Z1 exposure and a white (or lighter) wall for the Z7 exposure (mitigates non-linear meter response), use the same meter each time (mitigates, well, the obvious...), and use the modern Fuji GF670 camera (the modern electronic shutter is likely my most accurate and repeatable).

This is not a tightly controlled scientific experiment. It's a quick-and-dirty real-world ballpark baseline system check designed to keep my process chain from unknowingly wandering off into the weeds. As such, it sits squarely in the center of my sweet spot and has served me well.

Ken

MartinP · Sep 25, 2015

I can't help thinking that most variation between people is in their manner of metering, and that most variation in results for one person is in using different meters, apertures and shutters. Those are the bits to be worried about. Probably this is the same as what everyone is saying about checking what you do, rather than testing the film (which is probably the most consistent part of the whole photographic process)....

ColColt · Sep 25, 2015

I've always used box speed for a cloudy or overcast day. When the sun's out at a given time of the day(usually 11:00 and 3:00) and casting it's strongest shadows I go with half the box speed and develop accordingly. Seems to have worked since 1977(except transparencies of course).

Bill Burk · Sep 25, 2015

I proposed this test a while ago and am starting to use my own advice...

To find contrast...

Simple test: Take two shots, two f/stops of exposure apart. One at meter reading the other two stops different. Doesn't matter if you stop down or open up...

It's easy to do, and obvious which pair are the test shots.

If two stops exposure difference causes one stop density difference, then you can say you developed to about 0.50 contrast.

rbultman · Sep 26, 2015

Bill Burk said:
If two stops exposure difference causes one stop density difference, then you can say you developed to about 0.50 contrast.

Bill,

What is a one-stop density difference? Is this in densitometer parlance? I am trying to use a Pentax analog spotmeter as a densitometer with a light table. Is one stop = 0.1 density units, i.e. 1/3 EV on my meter?

Thanks,
Rob

rbultman · Sep 26, 2015

I think I answered my own question. A 4 EV range measured on the light table covering an 8 stop range of the scene equals 1EV measured per two scene stops.

Sent from my Nexus 5 using Tapatalk

Bill Burk · Sep 26, 2015

rbultman,

Sorry if I glossed over that. You are right, the goal is to have about a 50% gradient 0.50 so two scene stops turn into one negative "stop" of density on the light table.

0.1 density is 1/3 EV.

1 stop of EV is 0.3 density.

rbultman · Sep 26, 2015

Bill,
Thanks for the more precise answer.
Regards,
Rob

Sent from my Nexus 5 using Tapatalk

kossi008 · Sep 29, 2015

Densitometer Schmensitometer...
All it takes is a smartphone or tablet with a front cam, a desk lamp, and a calculator.

ColColt · Sep 29, 2015

Some of you are trying to reinvent the wheel. I can just see W. Eugene Smith or Henri Cartrier-Bresson worrying about densitometers and contrast indexes. Just shoot, develop and enjoy!

You can't possibly develop a roll of 36 exposures and get the same contrast index on every frame. Some negatives will be normal, some flat, some contrasty and others high contrast. The only way you have control over contrast is to shoot 4x5 sheet film and use a spot meter using the Zone System to develop according to the contrast range...N or N- or N+, etc.

If you consistently have little detail in the shadows, go from 400 to 250. Or, vice versa.

removed account4 · Sep 29, 2015

ColColt said:
Some of you are trying to reinvent the wheel. I can just see W. Eugene Smith or Henri Cartrier-Bresson worrying about densitometers and contrast indexes. Just shoot, develop and enjoy!

You can't possibly develop a roll of 36 exposures and get the same contrast index on every frame. Some negatives will be normal, some flat, some contrasty and others high contrast. The only way you have control over contrast is to shoot 4x5 sheet film and use a spot meter using the Zone System to develop according to the contrast range...N or N- or N+, etc.

If you consistently have little detail in the shadows, go from 400 to 250. Or, vice versa.

i see what you are saying
but if someone wants to be precise with their exposures
sometimes they have 35mm film and a few rolls in a few cameras
that have working / calibrated shutters and one camera is for N, another is N- &c.
thats how some people work as if it was LF with single sheets and specific development ..
which isn't reinventing the wheel it is just working methods.
in the end its about enjoying oneself ...

ColColt · Sep 29, 2015

You can do that sort of thing if you have for instance, an overcast day where all your negatives on that roll will be basically the same contrast. Conversely, if you're shooting the Klan's arrival in your town and want to go get some shots of those idiots in their white robes and it's 2:30 in the afternoon, sunny and the suns' at a 45 degree angle causing shadows as sharp as if they're drawn with an ink pen. You shoot the entire roll that way under those circumstances and just overexpose and under develop or use HC-110 Dilution H. Those situations you can determine a proper density range but not if you have a variety of conditions.

But, if someone wants to play there's no problem with that either.

philbed · Sep 29, 2015

I don't film anymore. Time is precious and I prefer shooting than testing.
As I print my pictures with a condenser enlarger, I follow Silvia Zawadzki advice from an old Photo technique magazine : from the manufacturer time and film speed, I shorten the developping time by 25% and decrease the film speed by a full stop. It works for me.

Bill Burk · Sep 29, 2015

ColColt said:
You can't possibly develop a roll of 36 exposures and get the same contrast index on every frame. Some negatives will be normal, some flat, some contrasty and others high contrast. The only way you have control over contrast is to shoot 4x5 sheet film and use a spot meter using the Zone System to develop according to the contrast range...N or N- or N+, etc.

I think you're not seeing the process control that you can get by developing film to a certain contrast index.

The whole roll of film gets developed to the same contrast index (except for a little variation along the strip, for example the core of the reel might get a bit more contrast) - individual shots will of course have different amounts of contrast and will need different contrast of paper when printing.

But my development time of 13 minutes and 30 seconds might not have the same results as your development time of 13 minutes 30 seconds.

While my film developed to contrast index 0.62 should compare well with your film developed to contrast index 0.62 (except I'll assume you took more interesting pictures than me).

I wish the Massive Dev Chart would list the contrast index that is to be expected for all the developing times that they give.

handle2001 · Oct 8, 2015

Alright to dig this back up I did some testing on a roll of Tri-X 120 in my new Yashica to see if I could get better results using a different EI. Here's the three shots I took of a static subject (please excuse the boring subject, I just used some stuff on a shelf in my office):
1:

2.

3.

4.

(1) was rated at ISO 200 (1/2sec @f/5.6)
(2) was rated at ISO 250 (1/2sec @f/5.6+1/3)
(3) was rated at ISO 320 (1/2sec @f/5.6+2/3)
(4) was rated at ISO 400 (1/2sec @f/8)

None of these have been modified in any way from the basic scan. For scanning purposes photo 4, the one shot at box speed, was much easier to work with to produce a nice image, but I haven't tried traditional silver printing yet. I also didn't try underexposing which based on this series makes me think might have produced a nicer image. It is entirely possible that the shutter speed on this camera is a bit "lazy", but I keep reading all this stuff saying that rating Tri-X at ISO 200 or 250 produces better images, and from what I can tell it just results in over-exposed images. Again, I haven't tried silver printing yet so I might change my mind about the denser negatives once I do.

Paul Howell · Oct 8, 2015

I do test, as I don't have a densitometer not as precise as others but keeps me the ball park. I don't consider my test is for true ISO, I am looking for my personal ISO or EI which is different for different camera and lens combos I use.

Stephen Benskin · Oct 8, 2015

handle2001 said:
Alright to dig this back up I did some testing on a roll of Tri-X 120 in my new Yashica to see if I could get better results using a different EI. Here's the three shots I took of a static subject (please excuse the boring subject, I just used some stuff on a shelf in my office):

(1) was rated at ISO 200 (1/2sec @f/5.6)
(2) was rated at ISO 250 (1/2sec @f/5.6+1/3)
(3) was rated at ISO 320 (1/2sec @f/5.6+2/3)
(4) was rated at ISO 400 (1/2sec @f/8)

None of these have been modified in any way from the basic scan. For scanning purposes photo 4, the one shot at box speed, was much easier to work with to produce a nice image, but I haven't tried traditional silver printing yet. I also didn't try underexposing which based on this series makes me think might have produced a nicer image. It is entirely possible that the shutter speed on this camera is a bit "lazy", but I keep reading all this stuff saying that rating Tri-X at ISO 200 or 250 produces better images, and from what I can tell it just results in over-exposed images. Again, I haven't tried silver printing yet so I might change my mind about the denser negatives once I do.

And the processing? Do you know the average gradient?

nworth · Oct 8, 2015

No. First of all, when you check the film speed, you are probably not testing the ISO speed. Testing the ISO speed is a very specific laboratory procedure specified by the ISO. You are testing the apparent speed, based on your equipment, developer, and technique. If you do it right, you include follow-on tests with real subjects to fine tune the speed for how you work and how you meter. You come up with and exposure index (EI) which gives you a working setting for your meter and reflects how the film works for you. That is important, but it is not ISO testing.

I don't even do that, mostly because I don't do that much work these days. The rated ISO speed, maybe with a tweek for the subject or the developer or the working condition, does well enough for me. I have enough experience so that the tweeks are usually (but not always) reasonable. I do sometimes run speed tests associated with developer testing. In these I will determine an EI for exposure on a lightbox using a standard film and developer; and then I do the same for the target developer. This is sometimes quite significant.

handle2001 · Oct 8, 2015

And the processing? Do you know the average gradient?

Processed normally in Sprint STANDARD for box speed. If I were to shoot the entire roll at an EI of say 200, would I then need to process the roll as if it were box rated at 200 ISO?

Bill Burk · Oct 8, 2015

handle2001 said:
Processed normally in Sprint STANDARD for box speed. If I were to shoot the entire roll at an EI of say 200, would I then need to process the roll as if it were box rated at 200 ISO?

No, when you alter EI for the purpose of improving quality (for instance to improve negative shadow detail), you develop it as if you shot at the rated speed.

In a negative/positive process, with deliberate overexposure to position the exposure on the film where you want it... you compensate by printing "darker". No change at all to contrast, you just print it down.

You should get essentially identical results between the different shots.

Your pictures don't have any shadow detail that's lost - so there's nothing that I can see to point out in your example picture... where you can take advantage of the better shadow detail.

So maybe you might want to take the camera outside and play in the wild. There you will find deep shadows where you can tell the difference between exposure examples.

Alan Klein · Oct 8, 2015

handle2001 said:
Alright to dig this back up I did some testing on a roll of Tri-X 120 in my new Yashica to see if I could get better results using a different EI. Here's the three shots I took of a static subject (please excuse the boring subject, I just used some stuff on a shelf in my office):

(1) was rated at ISO 200 (1/2sec @f/5.6)
(2) was rated at ISO 250 (1/2sec @f/5.6+1/3)
(3) was rated at ISO 320 (1/2sec @f/5.6+2/3)
(4) was rated at ISO 400 (1/2sec @f/8)

None of these have been modified in any way from the basic scan. For scanning purposes photo 4, the one shot at box speed, was much easier to work with to produce a nice image, but I haven't tried traditional silver printing yet. I also didn't try underexposing which based on this series makes me think might have produced a nicer image. It is entirely possible that the shutter speed on this camera is a bit "lazy", but I keep reading all this stuff saying that rating Tri-X at ISO 200 or 250 produces better images, and from what I can tell it just results in over-exposed images. Again, I haven't tried silver printing yet so I might change my mind about the denser negatives once I do.

#4 shot at box speed certainly looks the best to me also. My own procedure since I shoot landscapes and develop 120 roll film in an outside lab is to bracket my shots +1 and -1 from box speed regardless of the type of film: color or BW negatives or positive chromes. This allows for lab processing variables as well as my mistakes in calculating exposures. It also allows me to see different contrast ranges and select the final exposure frame I want to use.

Do you test your film for true ISO?