Do you test your film for true ISO?

[Steve Smith]

I have not tested any film for its ISO rating as I assume it to be correct. A few years ago, I read a few articles on finding your own EI for a film but found that the majority came to the conclusion that shooting at half the rated speed and developing with a 25% reduction in time worked for them. So I tried it and liked it so continued doing it.


Steve.

 

[Stephen Benskin]

How to rate the film is less about it's actual speed and more about personal taste, needs, and metering method. All of which is discovered through use. All of which isn't film speed but EI.

Apart from the Zone System testing, there's the Delta-X Criterion method (modified fractional gradient method) which the ISO standard uses. There are a number of recent threads in the Exposure section that discuss it's methodology. How a film is tested is directly related to the results. Anyone who thinks they are obtaining a film's "true" film speed with a gray card and exposure meter are misinformed.

To answer the OPs question. Because I have a calibrated sensitometer, I get the effective film speed from the sensitometric exposure when ever I do a processing check. It's not a separate procedure for me.

 

[Jim Noel]

Handle2001,

First, some terminology. The ISO speed of a film is the ISO speed. There is no trickery or secret. If you choose to set your meter to a different speed, that as an exposure index (EI). What you test for in the Zone System (or Barnbaum's book, which is particularly lousy on the subject of film speed), is an EI.

Also, here's something important which you won't find in The Negative or Barnbaum. The EI you test for using a Zone System methodology will be different from the ISO speed by a predictable amount. There is no fancy discovery when you find your Zone System EI. The reason it is typically lower than the ISO speed is merely a matter of methodology, and that methodology results in you looking for a specific density (the Zone System speed point or Zone I) 2/3 stop below where that density falls in the ISO criteria. This is why when people do their Zone System EI tests they almost invariably end up with speed from 1/2 to 1 stop slower than the ISO speed. These tests don't "reveal" anything, and they don't find a speed that is any more "real" than ISO.

So to answer your question, you can easily avoid the testing procedure for a Zone System EI. Just down rate 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.

I buy my film in large batches, all of same emulsion number. Each batch is tested for a correct EI using my standard materials and methods. Other than Kodak films, I never endup with an EI as low as 1/2 of box speed.
The chemicals and methods we use in our darkrooms differ greatly from the methods and materials required in the establishment of the ISO, thus the difference.

 

[Xmas]

I've not tested other than detecting some are underexposed.

But I still use the pre 1961 ISO I did not believe a word in the published marketing (~ Manure 100% organic).

I do test my meters, and shutters. I do compensate for shutter efficiency (with BTL shutters). I do read the manufactures data sheets. I do fix by inspection with A & B bath and HCA.

 

[darkosaric]

Box speed. I almost never take photos in darker than iso400, f2, 1/30s.

 

[Stephen Benskin]

I buy my film in large batches, all of same emulsion number. Each batch is tested for a correct EI using my standard materials and methods. Other than Kodak films, I never endup with an EI as low as 1/2 of box speed.
The chemicals and methods we use in our darkrooms differ greatly from the methods and materials required in the establishment of the ISO, thus the difference.

Curious to know your testing methodology.

 

[RalphLambrecht]

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 did it all the time and then
I found a shortcut: the boxspeed isthe true ISO and subtrscting 2/3 stop gives me my EI; works every time but the prof is in the print

 

[Kyle M.]

I always shoot everything at box speed and develop in a way that suits me. I have never used nor even seen a densitometer and I could really care less what one shows to be the perfect negative, I know what I want my negatives to look like and that's all that matters to me. They are my photographs that I take for my own viewing pleasure, what other people think of them matters not.

 

[blockend]

It depends what you're trying to achieve. If it's the maximum tonal range a negative is capable of offering, or you're looking for a more subjective, atmospheric "look" to an image. In smaller formats I'm not usually trying to achieve technical depth, but visual coherency, and achieving that can veer widely from box speed.

If you make friends with grain and contrast, there's a lot of room for experiment in film speed. If you want to be Ansel Adams, the parameters are much smaller.

 

[Bill Burk]

I test to find the contrast that I get with different developing times, not necessarily the rated speed.

I wish Massive Dev Chart gave expected contrast for the development times it lists.

In most cases speed follows from the contrast, but when you start experimenting with expired film then it helps to compare with known fresh film.

When you experiment with interesting developers like Michael R 1974, then you need to look at the characteristic curve. His straight line all the way to zero means that with a very low contrast development you get a higher than rated speed. That seeming contradiction can cause you to re-think what you always believed about film speed.

 

[fotch]

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.

+1

 

[Stephen Benskin]

Real speed testing involves a limiting gradient, not density.

 

[fotch]

Testing can be a second hobby for some and can include just about anything. What ever floats your boat.

 

[removed account4]

iso's and de velopment times are ballpark figures
i expose 1 stop over and develop a test sheet or test roll
to see what it looks like and go from there.
i don't have a lot of money or time to expend
on exposure and development tests so i "wing it" ..
i've been doing this for more than 3 decades, no problems.

but ...
if someone wants to do endless film tests, that is great !
its all about having a good time

 

[blockend]

Chemistry and physics are fascinating subjects, but it's also possible to find a film and developer that suits look you want to achieve, and stick at it. Thinking of my favourite photographers, most appear to have done their experimentation early on, then concentrated on their artistic vision.

 

[Gerald C Koch]

The technical term that you are referring to is WOMBAT1

1WOMBAT ==> Waste Of Money Brains And Time

Thanks for that new acronym which I hadn't seen before. Really like it.

 

[Doc W]

There have been quite a few posts in this thread about how testing is a waste of time and how the manufacturers test it before selling it. There is no doubt that one can shoot at box speed and develop as per manufacturer's recommendations, if you don't need control over contrast. However, I would venture that most of us don't get the results we want taking that route. if one does want control over contrast then testing, however minimal and brief, is necessary. You can do this in a day or two, or you can do it over a longer time, adjusting your exposure and development until you are getting good shadows and highlights. Either way works.

But I really don't get the big "harumph" about testing.

 

[Ian Grant]

There have been quite a few posts in this thread about how testing is a waste of time and how the manufacturers test it before selling it. There is no doubt that one can shoot at box speed and develop as per manufacturer's recommendations, if you don't need control over contrast. However, I would venture that most of us don't get the results we want taking that route. if one does want control over contrast then testing, however minimal and brief, is necessary. You can do this in a day or two, or you can do it over a longer time, adjusting your exposure and development until you are getting good shadows and highlights. Either way works.

But I really don't get the big "harumph" about testing.

Some people may be happy shooting at box speed and the manufacturers recommended developments time. Testing for effective EI and development time is quite simple and not particularly expensive and you optimise exposure and developing which ultimately makes printing (or scanning) much easier.

Ian

 

[Gerald C Koch]

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.

 

[Sirius Glass]

There have been quite a few posts in this thread about how testing is a waste of time and how the manufacturers test it before selling it. There is no doubt that one can shoot at box speed and develop as per manufacturer's recommendations, if you don't need control over contrast. However, I would venture that most of us don't get the results we want taking that route. if one does want control over contrast then testing, however minimal and brief, is necessary. You can do this in a day or two, or you can do it over a longer time, adjusting your exposure and development until you are getting good shadows and highlights. Either way works.

But I really don't get the big "harumph" about testing.

The key is "if one does want control over contrast then testing, however minimal and brief [emphasis added], is necessary." The problem is that the testinistas will spend their whole life testing and want everyone else to do endless testing so that the testinistas will be validated.

 

[Stephen Benskin]

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.

+1

 

[handle2001]

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.

 

[Sirius Glass]

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.

Just shoot box speed. If you like the negatives then the testing is done.
Otherwise derate the ISO by 2/3 of an f/stop and then the testing is done.
Life if good if you keep it simple.

 

[MattKing]

It isn't really though. The idea that somehow we're testing for all the other variables and differences between our process and Kodak's or Ilford's, is mostly myth.

1) In order to test for the other "stuff", the speed evaluation methodology should at least be consistent. But it isn't, so right off the bat, unless you understand basic sensitometry, you invariably misinterpret the results and come to erroneous conclusions. In the Zone System you look for the speed point 2/3 stop further down from where that density is in the ISO criteria (and there is a reason for this). That's really all the Zone System EI test tells people (except they don't know it, so they think they've discovered something about the film or their processes). Any test of deviations arising from our own stuff would have to start on that basis.

2) Regarding the other noise in our personal processes, unless you test every shutter speed on every lens at every aperture under every kind of light, you're not really calibrating anything

3) The typical Zone System test excludes flare, which under normal shooting conditions will change where the shadow to midtone subject luminances fall relative to where you place them, and the lowest values (ie the EI speed point) move the most. So, the idea that personal Zone System and EI tests somehow account for actual photographic conditions vs "lab ratings" is false.

4) People tend to view ISO speeds as some sort of scientific (or marketing) tool too far removed from actual photography to be of use to "serious photographers". In fact ISO speeds are rooted in tone reproduction and print quality - the very thing Zone System users are supposedly into.

Hi Michael:

I think you may have missed my point.

I was referring to the list of steps I take.

Which really don't test the film - they test what I do with it.

 

[Ian Grant]

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.

Unless you are following a strictly prescribed testing method ISO, ASA/BS or Din etc, then it's about testing personal EI and development time in the developer you've chosen and the Box speed is purely a starting point and yes that's quite different. However it's also testing the way you work.

Probably saying the same thing differently

Ian