[pure-silver] Re: Simple Step Wedge Testing
- From: shannon stoney <sstoney@xxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Mon, 14 Mar 2005 13:36:03 -0600
From: "Breukel, C. (HKG)" <C.Breukel@xxxxxxx>
Subject: [pure-silver] Simple Step Wedge Testing
Date: Mon, 14 Mar 2005 13:31:31 +0100
> The only point is I do not exactly = know waht to plot on the X
> axis: just the Stouffer step numbers, or 3.0 = (Zone X) minus the
> exact densities of the Stouffer steps, or..?..
I didn't exactly follow the procedure but the abscissa is usually log
exposure in lux-seconds, and the ordinate is optical density (or log
transmission-to-incident ratio). For a 100 speed film, the line should
break and make a toe at exposure of about -2. But the amount of light
incident to the film plane in camera is probably difficult to measure.
Quite frankly, I don't understand why people are so energetic about
determining film speed, etc. If I were shooting commercially available
films and papers, a couple of "clip tests" and eyeballing would get me
the normal contrast which prints perfectly with grade 2.5. Then I give
rather generous exposure to secure shadow unless flare is a concern.
There's not a lot of meaning in standardizing the film density at
certain point unless you are printing many negtives shot in the same
way, and printing with the same exposure. But this is just my opinion.
--
Ryuji Suzuki
"Keep a good head and always carry a light camera."
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