Then you have folks who want a negative to print well on both ordinary silver paper and some non-silver UV contact process. So that throws out some of the preconceptions too.
Then you have folks who want a negative to print well on both ordinary silver paper and some non-silver UV contact process. So that throws out some of the preconceptions too.
This is solved with stain...Originally Posted by Drew Wiley
With normal development each 3,75 stops then density rises additional 1.0D, so at 7.5 stops we are at 2.0D over B+F, so some 2.2D.
6 stops scene range we are at 1.6D + FB, so some 1.8D... IMHO this starts demanding a compression...
Seven stops is 2.1 log H and roughly divided by two is 1.05 density.
Your example 3.75 stops x .3 log units per stop is 1.125 on the log H over the range of which your film density will grow about half... 0.56
I am simplifying by saying half while ASA gradient is 0.62 and some Zone System users call N somewhere in the neighborhood of 0.55
Nice thing about what you’re doing Pere, since you’re making a computer program you only have to figure this all out once.
Haven’t talked much about flare, but the impact on the image is as if even straight toe film has a toe.
Pere - lots of those dual media types did not in fact employ staining developers. A few did; but older pyro formulas had a reputation for being unpredictable. We have more choices of them today. That's why a "thick negative", seriously overexposed, was espoused. But that strategy brought its own problems. The old thick-emulsion films (not to be confused with thick in the sense of over-developed) were more cooperative in certain respects than our current selection of basically thin emulsions. But they were a lot grainier too. And a lot of the anachronistic lingo and methodology of that era has become entrenched into Zone theory discussions, for better or worse. But even today, image stain can't do it all. We're lucky to have some excellent VC papers today that also help. But if you seriously overexpose, you can still get in trouble. Unsharp masking is another useful lasso to have at the rodeo. Gosh, the last couple of months I dug out some early overexposed negs and successfully reprinted them. The bigger problem was the dust marks and scratches of my early learning curve, when I was still loading film holders and even developing film in the furnace closet. Overall, what a headache! But it was worth it.
If one uses the zone system, that is, if they expose for the shadows and develop for the highlights, then using ASA 200 as the film speed will work fine. (I use HP5, and my tests have always resulted in using an ASA of 200.)
On the other hand, if one uses sort of an average value for exposure, then I wonder if the box speed wouldn't be sufficient. (I don't really know, because I don't meter this way.)
I understood the zone system much better from reading The New Zone System Manual by Minor, Zakia, Lorentz. Ansel Adams explanation is puzzling for me, especially with his emphasis on Zone V.
Neil, in that case all depends on how the scene is. With average metering, if we have snow around subject then we'll tend to underexpose, if we have a black background we'll tend to overexpose the subject...
but if it's a uniform scene, say a building in the shadow, then (with the ISO development) we'll get 0.62D +0.1D + Fog + Base. So around 0.92D average density.
If this exposure (box speed) is sufficient it would depend on how deep are the shadows, we know that at well metered -3.3 underexposure we will obtain 0.1D over fog+base, this is a very well defined reference point.
Thanks! Development is advancing nicely, it's my hope it would be useful...
Averaging is kinda like political polls. Sometimes they predict correctly, sometimes they sure as heck don't. And averaging bears quite different implications for color photography than for black and white, because you're concerned with what color hues saturate at a given exposure level, whereas in black and white work its a much longer gray scale. Earlier this afternoon I was out on the shoreline with color film for some nice light, and I knew exactly which foliage greens would correspond to middle gray, even though they were not gray in color at all. And I knew that the backlit fresh grass needed exposure one stop above that to look like the radiant color it was. But in black and white work, I could have placed the grass anywhere I wished relative to how I wanted the overall scene interpreted. I could underexpose it and develop strongly to emphasize highlight gradation, or I could conversely overexpose it to favor significant shadow gradation, just to mention two of many possible options. We make our own rules, and are free to change these rules from image to image. But that persistent little red triange in the middle of the meter does serve as a convenient reference point; so I'm certainly not surprised that AA standardized his conversation around Zone V.
Drew, of course one thing is sensitometry and another one is a practical shot.
All we know that "subject's color vs meter spectral sensitivity vs film spectral sensitivity vs filter" has an impact. And many other inaccuracies may follow.
Sensitometry simply explains how a medium-processing combo works, but we have other important factors, of course. Then we may start speaking about what an image has inside it...
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