[rollei_list] Re: JOBO development tips

  • From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
  • To: <rollei_list@xxxxxxxxxxxxx>
  • Date: Mon, 16 Dec 2013 16:06:21 -0800

----- Original Message ----- From: "CarlosMFreaza" <cmfreaza@xxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Monday, December 16, 2013 8:17 AM
Subject: [rollei_list] Re: JOBO development tips

I couldn't share my experience with you because I do manual B&W film processing and never used an ATL 1500 nor prewash;anyway developing times have to do with the negative contrast, I think you need to find the best neg contrast for your purposes, f.e. print via
condenser (flatter negatives) or diffuser enlargers ( higher
contrast); it looks like a contrast for a diffuser enlarger is better to scan negs for digital prints. BTW, variable contrast papers and their filters help very much to compensate the negative features and
the differences Condenser vs Diffuser enlargers are not so


The presoak affects the take up time for the developer so it has some effect on total development time for a given contrast. The effect depends on everything, film, temperature, developer, and must be determined by experiment. Kodak used to recommend a pre-soak for processing sheet film by hand to prevent the sheets from sticking together when first introduced to the developer. I think JOBO recommends a pre-soak to slow the penetration of the developer when it is poured into the tank so as to eliminate streaks due to uneven development. To add to what Carlos says above, Kodak philosophy was to standardize development contrast based on the expected type of printer with an aim gamma to match "normal" grade paper and then chosing contrast grade to correct as necessary. This is as opposed to zone system processing where development is adjusted to obtain a fixed negative contrast based on the scene contrast, again so that all print on "normal" grade paper. The problem is that the reproduced contrast of a scene may be considerably distorted from the original contrast even though the entire range of brightness will be reproduced as shades of gray. the Kodak method gives you essentially 1 to 1 brightness reproduction for some selected range of scene brightness. The eye likes to have mid-gray tones reproduced 1:1 even if shadows and highlights are compressed or clipped, otherwise the scene may look grayed out or overly contrasty. Development charts vary with manufacturer: Kodak charts used to be based on suitable contrast index for diffusion printing sources, about one paper grade more contrasty than ideal for a typical semi-diffusing condenser source while Ilford uses a compromise value. In any case, as Carlos points out, with variable contrast paper this is of little significance since the print contrast can be adjusted for best visual effect from any reasonable negative.

Richard Knoppow
Los Angeles

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