developer dilutions - why, and development time comparisons

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following the advice of experts here on this forum, I have found good working parameters for developing Delta films. I am trying to understand the rationale behind dilution of developers. why diluting XTOL 1:2 and greater is preferred for highter EI ranges? why is this? the increase in development times are not linear, so is it all empirically derived or are the adjustments calculable?

finding something that works at EI1600 (Xtol 1:1 15'@75degrees), leaves me guessing for both EI3200 and launch times for Delta 400. suggestions?

-- Daniel Taylor (aviator@vernonia.com), August 01, 1999

Answers

Virtually all development times are empirical. The manufacturer's data in their technical data sheets are nothing more than recommendations. The basic rule is "If it works for you, it works for you!" (Courtesy of Hicks/Schultz: The B&W Handbook, which, btw, is worth reading in this context).

From what I understand, the designing of emulsions and of developers has something of a black magic. As a rule of thumb, one can say that strongly diluted developers act less energetic and somewhat compensating, because the active agents are quickly consumed in the dense areas of the negative and remain active in the thin (shadow) areas.

You might find some rule of extrapolation for calculating a first approximation of development times at dilutions other than the one given. However, these, too, are no more than first approximations, or parameters for a first test.

-- Thomas Wollstein (thomas_wollstein@web.de), August 02, 1999.


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