[pure-silver] Re: Delta 3200 Processing recs.


----- Original Message ----- From: "Shannon Stoney" <shannonstoney@xxxxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Thursday, August 27, 2009 6:29 AM
Subject: [pure-silver] Re: Delta 3200 Processing recs.


I rate it at only 800, regardless of the processing times. I did some tests and found that the speed didn't change even with long processing times. Plus the long processing times caused extreme graininess as I mentioned in my earlier message.

--shannon

There really is no such thing as "pushing" film to a higher speed. What happens is that the overall contrast is increased and along with it the toe contrast. When film is underexposed the shadows are placed on the very low end of the toe where contrast is minimal. Increasing development can increase the contrast there to printable values but the parts of the curve receiving higher exposure can be moved up to very high contrast so that the negative becomes hard to print reaquiring a lot of manipulation. I think the very high speed films like Delta 3200 have modified curves such that they will take more overdevelopment without the mid-tones becoming unprintably contrasty. The ISO speed measuring method dictates development to a specified contrast. This contrast is about right for contact printing or diffusion enlarging. When some other contrast index is used the speed will change and there is a table in the standard for obtaining a correction factor. Films like Delta-3200 and Kodak's equivalent measure about EI-800 to 1000 when using the ISO method but can be "pushed" and still present printable negatives. The 3200 in the name indicates the speed the films are optimised for although they can be shot at EI-800 to as much as EI-64,000! The latter if the subject matter is very low contrast and if copious grain is acceptable. These are grainy films to begin with and increased development will make them even grainier. That is the price one pays for the extreme speed and the grain is likely finer than slower films when pushed very much.

--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx


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