Revolving developing times

**alnegri** · 30-Mar-2007, 06:55

Hello.
I am new of large format;
I just bought a Jobo tank 2523 (manual revolving for 4X5).
The question is: how much have I to decrease the developing time of the inversion tecnique I usually use for the 35 mm films?
How many revolutions in a minute? (I suppose I can't stop during developing ).

Thansk in advance.
Alberto

**Ron Marshall** · 30-Mar-2007, 07:19

Welcome to large format Alberto. Around 50 revolutions per minute. You can stop turning it very briefly.

Anchell and Troop, and many others recommend a 20-30% increase in development time going from 35mm to sheet. They also recommend a 20-30% decrease going from small tank intermittent to rotary. So try your 35mm small tank times unchanged as a starting point. But test a couple of sheets to be sure.

Good luck!

**steve simmons** · 30-Mar-2007, 07:33

You should really test for your personal Exposure Index and development time. There is a simple procedure for dong so in an article in the Free Articles section of the View Camera web site

www.viewcamera.com

You should not extrapolate EI and dev. time from one format to another. You may be using a different meter, emulsions are not necessarily identical, and agitation is different.Doing this test is not that muchwork and will set you for a long time.

steve simmons

**Remigius** · 30-Mar-2007, 07:38

Hello,

I'm not very experienced, but I can't think of any reason to do a longer development for sheets than for 35mm as such. However, I agree with the reduction for the rotary development. I also presoak my lf films for a few minutes (but not the 35mm). There are two sites I use as a reference for my decisions about development times, one of which is in German, but includes a calculator to account for different temperatures, push/pull and procedures:

http://www.digitaltruth.com/devchart.html
http://www.phototec.de/infomag_erechner.php

If you search on this forum you'll find many helpful advices about processing.

**alnegri** · 30-Mar-2007, 10:19

Thanks for all the usfull informations and links.
Alberto

**Gene McCluney** · 31-Mar-2007, 01:04

Originally Posted by Remigius

Hello,

I'm not very experienced, but I can't think of any reason to do a longer development for sheets than for 35mm as such. .

Most photographers want or need more contrast out of their LF negatives. The standard has always been a more "vigorous" negative in LF over minature formats (35mm) where you are more concerned about minimizing grain. It is easier to "block" highlights with minature (35mm) films due to overdevelopment.