I just read something in some Kodak literature that I've never noticed before. In some literature about development times for some film, it says that the recommended times are for diffusion enlargers and to reduce the times by 20%-30% for condensor enlargers.
I've never noticed anything like this before, so I've never reduced any times I've found before. I don't really ever having a problem, but I guess I should ask the group. Have I been missing the boat here? Anyone else seen this little note in the tech data? Thanks.
I believe that note has been part of their tech data for quite some time.
I thought it is that developing times are based on condenser enlarger and to use 20 % more time for diffuser type.
I rememeber being told by a professor that the times manufactures gave were usually for diffuser enlargers, and that matched my feeble attempts at E.I. testing...
Both films I have tested (35mm tri-x and 120 macophot up 100) tested pretty dang close to what a diffuser would need on the high values, folllowing manufacturer's specs (efke specs for the maco).
To kind of enforce the point, I was the only one printing with diffusion heads in my class, and everyone else had to drop dev times at least 20-25% to print on condenser.
Keep in mind that my ignorance is only surpassed by my faulty memory, so don't hate me if I'm wrong.
I think it's already been covered here, but for clarity's sake here's my two cents' worth,...
Diffusion light sources (aka dichroic colour heads) are typically lower in contrast than condenser heads; therefore (B&W) film is usually developed slightly longer to correct for this. It's all relative.
In densitometric terms, it's as follows:
Zone I exposure: 0.10 above fb+f (up to .20 a la Mr. Hutchings)
Zone VIII exposure: 1.25 to 1.35 (net) above fb+f for a diffusion enlarger
Zone VIII exposure: 1.15 to 1.25 (net) above fb+f for a condenser enlarger
For the sake of reference, your Zone V exposure should be as follows:
Zone V exposure: 0.65 to 0.75 (net) above fb+f for a diffusion enlarger
Zone V exposure: 0.60 to 0.70 (net) above fb+f for a condenser enlarger
Kodak used to publish development times for condenser enlargers. Several years ago they changed their times to use diffusion enlargement as the standard (probably has to do with all the color heads in use).
Thanks for the clarification. I was looking at a 1974 Kodak time & temp chart. The times back in those days were for condenser. I guess that shows my age.