how to tell developing time with custom agitation?

[stig tvenge]

There are probably treads out there already on the subject, and I belive Ansel A wrote something in his books about it as well ... For the past year I've been doing 4x5 in my darkroom, but I didn't feel fluid and "in control" over the prosess. I had been doing the devoloping in some 6x8'' black blastic containers, one sheet at a time laying flat on the bottom ... But somehow I felt the results where kind of random with manual aggitation, and all the Jobo drum roll stuff I found was expensive and far away .. so I ended up with a platform rocker :

http://www.bellcoglass.net/products/7740-10000.jpg

I want to : do some kind of benchmark, and find out the best speed on rocking, and find out how much or less time I need to get my zones where I want them ... ??? Is there a rule of thumb, or a quick way to test this? I have a zonecard with the 11 zones, and do I just test my way from this? I belive I need a full scale, to do like +1 devlops ... maybe even a graph? Does anyone have something custom to aggitate their tanks, and how did you figure out time and .. intensity ??

[Ed Pierce]

I would approach this by setting the unit to a gentle, constant agitation, and leave it there. Then run your developing time tests. Make sure your temp is constant.

[ic-racer]

Is there a rule of thumb, or a quick way to test this? ??

The quickest and easiest is to run some test strips and plot something like platform speed vs gamma.

Without a sensitometer or densitometer, you can do the common "Zone VIII" test. That is, print a Zone VIII frame at a time that produces min-exposure-for-max-black on the film edge and see that it prints to just off white. If it prints totally white, then decrease agitation or time. If it prints gray, then increase agitation or time.


Personally if I were testing that I'd not care how the agatation affects gamma (because you can adjust overall time accordingly). I'd be worried about un-evennes from over or under development at the edges or center.

I'd fog some 4x5 sheets with an even fog then process them at various settings. Then check for difference in edge vs center density. Standardize on the agitation setting that gives the most consistent results and then do the Zone VIII test to adjust the time.

[Martin Aislabie]

Buy a BTZS Film Test from Fred Newman ?

Fred exposes the film for you, you develop it, send it back to him and he measures it, sending the results back via a PDF -http://www.viewcamerastore.com/product_info.php?cPath=35&products_id=82

Personally, I would sacrifice some film to a few of your own experiments before doing the BTZS tests.

Begin with the lights on, insert film and developer then check the developer flow patterns.

After you are satisfied, shoot some film of a very out of focus uniform object (concrete wall or similar) and then try your development technique. Review and even print the negs to check for uniformity of tone

When satisfied go for the BTZS tests

Martin