Two bath (a.k.a. split) D 76greenspun.com : LUSENET : B&W Photo - Film & Processing : One Thread
I came across a formula for split D 76 and was thinking of using it with films like TMY and Fomapan T 200. I heard great things of Emofin, a two bath developer, for increasing speed and controlling contrast.
Ok, I can expect contrast control due exhaustion of the developing agents in the highlights, but how about things like TMY at 800-1600?
BTW, any ideas about agitation, as bath A is an absorption process, moving should not hurt, while in B there is plenty of borax and the developer located as the limiting factor within the emulsion, movment should not hurt either.
Final note: The sulfit is split 50/50 between A and B.
-- Wolfram Kollig (Kollig@ipfdd.de), June 16, 2000
For Emofin I've read that one should only agitate the first bath, and let the second bath stay still. Hmmm, maybe one agitation at the beginning of the second bath wouldn't hurt, and it would be easier to get rid of possible bubbles on the film. I hate bubbles. :-|
In Champagne bubbles are ok, but that has nothing to do with film developing.
...well, maybe if the job was a success one can celebrate with a glass of Champagne!
-- Patric (firstname.lastname@example.org), June 16, 2000.
You are probably right about the first bath. Agitation will not have too much of an effect there, assuming that the recommended developing is that for a saturated emulsion. Then, the concentrations of developing agent in the emulsion and in the solution are in equilibrium. However, agitation might shorten the time to equilibrium.
I would expect agitation of the second bath to have the same effect as with conventional one-bath developers. However, Emofin is not a dilute one-shot developer, and I would not expect a pronounced edge effect due to the local depletion of developing agent near edges.
-- Thomas Wollstein (email@example.com), June 16, 2000.
According to "The Darkroom Cookbook" in general, agitation is not a critical issue. However, they do recommend a few gentle inversions every 30 seconds in the first bath and continuous, but gentle agitation in the second. For the second either slow and gentle inversions or gently swiching the film around.
-- Terry Carraway (TCarraway@compuserve.com), June 16, 2000.
Thanks to those who have responded. In practice I used Fomapan T200, exposed at 200 ASA and T800, exposed at 800 ASA, heavy agaition in the first bath for 4 mins @ 220C and no agaition in the second bath. The T200 was way off its 200 ASA, as there was nothing in Zone 1 AND 2! Dmax at the leader was around 1.8 (so 1.5 above base). On the T800 was almost nothing at all. Next test T200 but this time 5 mins with agaition in second bath, looks better with Dmax around 2.1 (so 1.8 above base), but still slow film speed.
Since increased agaition in second bath only gave a slight improvment in film speed, it seems that the absorbed amount of developer is the limiting factor. The first bath contains 1.75g Metol and 6g Hydrochinone per litre. The next test will be on old style emulsions (Forte 400 and HP5+) trying to estimate their speed. If their speed is also too slow, I might increase the concentration of developing agents by 100%.
The best way would be a rather strong first bath, so that contrast could be controlled by time in the second bath.
-- Wolfram Kollig (firstname.lastname@example.org), June 19, 2000.
The times when I tried Divided D76 with TMX and TMY were not great. The emulsion is to thick for the 3 min Bath A and 3 min Bath B to get good results in my opinion. With the older non T-grained emulsions, it works GREAT!!! I have done alot of different tests with this and have come up with the same thing... thin negs, even with a 5 min. Good luck, Scott
-- Scott Walton (email@example.com), June 19, 2000.
I think the problem is that the emulsion is too THIN. It doesn't hold enough Part A to do the job.
-- Terry Carraway (TCarraway@compuserve.com), June 20, 2000.
If you want a 2 bath developer, try Diafine. It works great with all films I've tried(120 Kodak Tmax 100 and 35mm HIE, Ilford HP-4 and 750 IR). I even use it with tech pan (35mm and 120), shortening the B bath time to exactly 60 seconds.
-- Gene Crumpler (firstname.lastname@example.org), June 20, 2000.
Thanks Scott, you are right. Using HP5+, I did get full speed (Zone 1 was just visable at 400 ASA) and a Dmax below 2. But this system seems not be ideal for pushing, so I'll try Emofin for the theatre festival.
-- Wolfram Kollig (email@example.com), June 23, 2000.