Bob, I would be interested in hearing your comments.

Below are a few photos from my recent flurry of film development activity. All were developed using Barry Thornton's 2 bath developer in Jobo Expert Drums on a Beseler roller base. The first photo is a 5x7 on Arista.edu Ultra 200. The second is from 4x5 HP5+. The third is a part of a whole plate negative made on HP5+ (The scanning area on my scanner is not big enough to scan the whole negative). Without film holders for the larger sizes, I just lay them on the glass emulsion side down and flip them in Photoshop.

I regularly develop some combination of HP5+, FP4+, Delta 100, or Arista.Edu Ultra 200 together in the same drum. I print in the traditional darkroom, but I do quick scans to view on screen so I can decide which negs to print (sort of a digital proof sheet). These have had minimal processing in Photoshop so I feel comfortable putting them up for public view. In my experience, these negs will print well on grade 2 or grade 3.

Sandy King recommends using Divided D23 diluted 1:1 for four minutes in each bath when used for rotary processing. My experience using Thornton's similar two bath formula supports this recommendation. Thornton recommended 5 minutes in each bath when processing sheet film using intermittent agitation. I found that the rotary processed negatives are too contrasty if the A and B baths are used full strength. This indicates that constant agitation has an impact on two bath developers, and that assertions to the contrary based on the idea that development stops once the developer absorbed into the emulsion during the A bath is exhausted are just plain wrong. Perhaps the constant agitation in the B bath causes some of the developer absorbed into the emulsion to go back into solution and work on the highlights.

Based on my experience using Thornton's two bath for years, tray development with intermittent agitation using the two baths at full strength for five minutes in each bath resulted in a noticeably less contrasty negative than one processed at full strength for the same times with constant agitation. The constant agitation makes it easier to blow out the highlights, so I have to be more aware of the scene's contrast using the 2 bath with constant agitation than when I was tray processing the negatives.

I wondered whether the increased contrast was due to development in the A bath. However, I don't think much development takes place in the A bath, even with constant agitation, since I mix Thornton's formula with 40g/L of sodium sulfite in bath A and 40g/L in bath B (sort of like Vestal's DD76). Diluting this 1:1 leaves only 20g/L of sodium sulfite and nothing else to act as an accelerator. Maybe one of these days I will run a few sheets through the A bath only and see if any development occurs, and if so, how much.

Thornton suggested that you could use a different B bath in N+1 or N-1 situations. I have not tried the N+1 with the rotary processor, but have tried the N-1 formula. A few of my 4x5 negatives from a recent trip came out with blown highlights when processed normally. I mixed up some B bath with 7g/L of Sodium Metaborate instead of the standard 12g/L used for N processing. I diluted this and the A bath 1:1 and processed the backup negatives for four minutes in each bath The results were very good. There was much more detail in the highlights and I think the negatives will print well. (The third photo was processed this way.)

I also found that the diluted baths are reusable for at least one day. I have run 30 4x5 sheets using the same baths with no problem, and discarded the diluted solutions at the end of the day.

Photos (c) 2009 David C. Karp