Unless one is using a particular process which results in a speed loss, the original Zone System EI test is indeed factually superfluous. However to answer Christopher's specific question, shooting a full scale target as proposed introduces flare, and flare will tend to cause an increase in EI.
Thank you Doremus for your thoughtful response, a method you have detailed in the past, and I have found helpful, especially since I don't have easy access to a densitometer and prefer Pyrocat HD.
I agree. Rating at about 1/2 "box speed" builds in so much "reassurance" factor that the image is going to get recorded, no matter what.Originally Posted by Kirk Gittings
But I have abandoned that method now that I can dependably, inexpensively, and easily test my shutter speeds with a $20 photo transistor circuit and an app in my iPhone. That and my standardizing on Xtol as my "universal developer."
So far with accurate shutters, Xtol and T-Max 100 and 400, Tri-X, HP5, Fomapan 100, FP4+ and Acros 100, box speeds are dead on. (After all, box speeds are the result of a lot of testing by manufacturers.)
I think testing serves the purpose of compensating for shutter inaccuracies and personal agitation patterns in using various developers. Knowing my shutters are accurate to begin with removes exposure variability from the equation. And Xtol (beside its beautiful image characteristics) seems to remove processing variation.
Rich
The experienced darkroom worker's established exposure and development times can be used to duplicate the response of unknown materials using one's sensitometric data in the darkroom.
For example if film A gives good results with a speed showing 0.1 log d above film base plus fog when processed to a gamma of 0.8, then film B might also give good results under the same conditions.
Likewise, in terms of printing, if film A gives good results under you enlarger with a gamma of 0.73 then film B might do the same.
All the trial-and-error to match these sensitometric results can be accomplished in the darkroom.
If one never changes materials and has unlimited time resources for trial-and-error testing in the field, sensitometric testing is not for you.
I have all the tools, shutter speed tester, densitometer etc.and use them if I see some anomaly. Otherwise what I do is nailed precisely for what I need with one film and developer, FP4+ and Pyrocat HD.
Thanks,
Kirk
at age 73:
"The woods are lovely, dark and deep,
But I have promises to keep,
And miles to go before I sleep,
And miles to go before I sleep"
Doremus,
That's because it seems to take about a year of badgering for someone to believe me.
Well, I believe you nowDoremus,
That's because it seems to take about a year of badgering for someone to believe me.
Agreed. I think it's partly because most people don't hold a clear definition of "film speed"; and partly because most aren't actually interested in what is film speed, but only how to achieve consistently adequate results. They wish to have just enough knowledge to maintain a sense of control over the materials, as is true for much of the what we deal with in our daily lives. Questions concerning b&w film speed by photographic enthusiasts tend to center around the methodological, while generally ignoring the theoretical. For example, what is the explanation for the fundamental concept of stopping down 4 stops from the exposure meter reading? I've seen very little skeptical push back within the popular photographic community as to whether this is a valid assumption in which to base a b&w film speed test. What about the tendency to not questions the conditions under which the testing is supposed to be performed, even when those conditions are missing from the stated methodology, e.g. light source.
BTW, Henry tends to focus on good scientific testing practices.
Last edited by Stephen Benskin; 3-Jun-2017 at 15:15.
Stephen,
I agree with you completely. As a practitioner, I'm not really interested at all in where the film speed point on my film is (as you so astutely note). Only what E.I. I need to use on my meter with my metering techniques to get the shadow detail I need. I try to keep that E.I. as high as possible to get close to "minimum exposure for adequate shadow detail," but tend to err on the side of overexposure when in doubt. I have no illusions that the film's actual ISO is anything else but what the manufacturer says it is. Nor do I have any illusions about the variables in my metering, exposure, development, printing workflow. Getting a negative containing the information I need to make a print I like is all I need to be happy.
That said, I tend to worry when if my E.I. is much different from the stated ISO; that usually indicates some problem on my side of things. I understand the theory behind determining ISO, or even finding speed points with different materials/developers/exposures. I'm also aware how some systems, notably the Zone System, vary from ISO procedures when determining film speeds. This helps me when problems arise or I'm "testing" a new film. Still, I don't think I've ever tested a film for its speed point; rather, I find an E.I./development time combination that gives me an acceptable black where I want it and the desired shadow detail/separation above, while keeping the highlights where I want them. All this is completely subjective. Many think they are being "scientific" when they are really not.
Enough rambling...
Best,
Doremus
It's all fine as long as there is awareness. Otherwise, not only can it potentially be a waste of time and materials but also counter productive.
Last edited by Stephen Benskin; 4-Jun-2017 at 13:04.
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