Archived posting to the Leica Users Group, 2001/05/03
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]At 09:00 PM 5/3/01 -0500, you wrote: Folks, I just went through an series of tests matching EI and curves of three films given ordinary intermittent development and continuous rotary agitation (Jobo). The films were given a _one-minute_ presoak to avoid airbells. The reason for not presoaking longer is that Phil Davis has already shown that various films show all sorts of changes in characteristics when given a presoak that long; therefore there's no point to doing it. In order to match characteristics, Delta 3200 in DD-X 1:4 required a 15% decrease in development time in changing from intermittent to continuous agitation, HP5+ in D-76 1:1 required a 25% decrease, and Delta 100 in D-76 1:1 required a _35%_ decrease. So you see there's no consistency in how much development compensation is required for changing from intermittent to continuous agitation and vice-versa Other tidbits are that HP5+ and Delta 3200 retained the same EI, while Delta 100 lots 2/3 stop in speed for the same CI with the change to continuous agitation, or, iow, it went from EI 160 to EI 100. The curves for each agitation method matched its counterpart virtually exactly once the proper development-time compensation was used. So...I'd suggest that if you're trying to find a reasonable development time for one method and all you have is a time recommendation for the other, don't be afraid to make a radical change in development time; it may be just what's needed. John Hicks jbh@magicnet.net