I often do a sanity check with incident meter. They typically agree. But I would listen to Mark Barendt he uses incident meters / duplex metering...
Originally Posted by AndreasT
My ears are burning. Thanks Bill.
Andreas, the 2/3 stop adjustment to EI that has been talked about here works regardless of meter type. An EI can factor in whatever bias the photographer wants. The ZS simply factors in a preference for more shadow detail than ISO standard.
The real questions are: does it help you get better prints? & what do you have to give up?
Mark Barendt, Beaverton, OR
"We do not see things the way they are. We see things the way we are." Anaïs Nin
Yes, but not on purpose. It's not part of the design.
Originally Posted by markbarendt
In broad terms, the goal with ZS EI testing (fixed density) appears to be the exposure of shadow detail on or close to the straight line of the curve. According to Adams, important shadows should normally be placed on Zone III. For texture/detail to exist within an average Zone III value, we must have a range of values, say at a minimum Zone II to Zone IV. It then follows at a minimum you'd want Zone II on the straight line. In practice, with most current films, when you follow the typical Zone System EI test (meter, close down 4 stops etc, 0.1 above B+F etc etc), I have found this is more or less what you get. You can take this as far as you want. Barnbaum, for example, advocates using half the ISO speed and placing important shadows on Zone IV.
However the assumption the shadows need to be on the straight line is a Zone System principle. It is not based (as far as I know) on the first excellent print studies or fractional gradient speed method, where some compression in the shadows seems to be acceptable, as long as the shadow gradient is related in a specific way to an average gradient.
On the face of things, if you buy the first excellent print studies, it would seem ZS EIs give you a safety factor rather than improving print quality. Perhaps ZS EIs also give you some more flexibility when interpreting the negative. Whatever you want to call it. What do you lose by giving extra exposure? Under normal circumstances, not much (besides the loss of speed). Technically, overexposure results in increased granularity, irradation and halation (both contributing to lower acutance). But with current films are these effects even material? Probably not when we're talking a half to one stop.
It is important, however, that as you reduce development to accomodate scenes of a higher contrast range, the difference between ZS EIs and fractional gradient speeds increases. Since the fractional gradient speed is based on a shadow gradient in proportion to an average gradient, it is that relationship which must be maintained to produce excellent prints, not a fixed density. Clearly with a fixed density criterion (ZS), the more you reduce development, the more you have to reduce the EI. This doesn't appear to be the case with fractional gradient speeds, at least within a reasonable range. So, relative to the first excellent print criteria, ZS EIs in "minus development" scenarios result in increasing amounts of "overexposure". What are the costs under these circumstances (besides more speed)? Well, slightly more of the image characteristic effects stated above. What are the benefits? Unclear.
Originally Posted by markbarendt
It is important for me to know what is going on.
I believe it is important to know the variables to possibly be more flexible in the field. There were a lot of things which I could not answer. Now I know a bit more which of course results in more questions.
It is time to try this out, all the variables and see what results one gets.
The thing with the Delta-X makes perfect sense when actually looking at the curves.
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Michael, I don't believe your theory about the goal of the Zone System has any merit. The EI difference is simply a remnent from before 1960. I guess you could consider that the Zone System didn't have to change with the change in the ASA standard because it was achieving it's goals. You could also consider, it was luck that there was a correlation with the ASA method because of the safety factor in the ASA standard which compensated for the Zone System not incorporating flare. Otherwise an excellent analysis.
Last edited by Stephen Benskin; 03-18-2013 at 12:33 PM. Click to view previous post history.
I'm just talking about what people are trying to do when they run ZS EI tests, and what is at stake in terms of image quality etc when one chooses a different EI than the ISO speed. ZS testers are trying to find an effective film speed such that given their processing procedures, when they meter and close down two stops for shadows, they get full separations in the negative. So I don't understand how it is a question of film speed at all. ZS tests are just exposure/development tests to get a desired tonality. Whether or not they get what they think they are getting is another matter.
I've edited the post. My original respnse was based on a quick scan of your post. Sorry about that.
Originally Posted by Michael R 1974
The luminance range of the standard model is very similar to the Zone System's. In fact, it has 1/3 stop deeper shadows. So instead of the ZS 4 stops, the statistically average luminance range as 4 1/3. According to the Delta-X Criterion, the fractional gradient speed point falls Δ0.29 log-H below the 0.10 density point. This is where the shadow exposure for the standard model would fall in a no flare situation. With flare, the shadows are pushed up to around the 0.10 density point. The ISO standard and Delta-X Criterion use 0.10 density as the speed point. Mostly because it is an easy to find point of measurement, but partly because this is where the shadow exposure will fall. As the ZS has practically the identical luminance range below the metered exposure point, it would go to reason that the shadow exposure will also be brought up to ~0.10 under normal shooting conditions. The ZS test is practically flare free, so the exposure four stops down from the metered exposure point will fall 2/3rd stop below 0.10 density. By increasing the EI 2/3 of a stop, in the no flare testing, exposure then falls at 0.10 density, but with most general purpose developers, if the EI was left at the ISO and an average scene was shot without exposure compensation, flare would bring the shadow exposure up to around 0.10 density.
The example shows just that. The no flare curve's shadow exposure (Zone I) falls at a density of 0.04. With a one stop flare factor, The Zone I exposure falls at a density of 0.12.
With a lot of my films when I apply the Delta-X (sounds like a secret fighter plane) or the CI ruler my speeds tend to jump about.
Meaning some of my minus curves have more speed than the normal, and the plus curves too. etc..
Now not with all film, or should I rather say not with all developers.
Now some surface developers/compensating developers, or what ever they are technically called have a different spread at the toe region where the curve goes up.
What does one do here, or have I missed something again?
Can this be normal?