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.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.
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
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.
The technical term that you are referring to is WOMBAT1
1WOMBAT ==> Waste Of Money Brains And Time
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.
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.
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.
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.
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.
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.
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