Re: [Leica] Erwin Puts' test for film speed

[Erwin Puts <imxputs@knoware.nl>]

>
Robert,

Slide film has a different characteristic curve from B&W film. The 
curve is steeper in the case of the slide material and the shape of 
the "toe" (the lower densities in case of a B&W negative and the high 
densities in case of a slide film) of slide film is short and steep. 
As you know, by push processing the shadows hardly improve, only the 
middle values and the curve will be a bit steeper. So this action 
(steeper gradient) and character (short toe) might reduce the -3 and 
- -4 frames into deep black (no details visible).
Generally when you use B&W negative film at its correct ISO speed, 
you will hardly notice any texture or grey density in the -4 frame. 
So the slide film is not at a disadvantage in normal processing and 
use. Zone System workes habitually lower the ISO value by 1/3 or 1/2 
to get density into the  -4 frame.
Your questions:
Have I used your method correctly and is
slide film about one stop less able in recording shadow details as compared
to print film?  Should I try rating the film a little slower to get the
fifth exposure discernable from base fog?

Yes the method is correctly applied. Slide film has about the same 
ability to record shadow details. I tested recently all 100 and 
200ISO color neg and slide films and used a densitometer to measure 
the grey scale. Slide film was not at a disadvantage here. But when 
pushing you loose a bit. To lower the exposure to get the shadows 
back and at the same time deciding to push the film will cancel out. 
If you need shadows you cannot push (or you should overexpose 
consciously when taking the picture, being aware of what you are 
doing) and if you need pushing you lose some deep shadows.

Erwin