Thank you for doing this test,
I have taken the liberty of attaching a D-log E curve from the British Journal of Photography 10 Nov 1999, article reporting work by C T Blood.
CTB Developer-working Solution:
Develop Delta 100 10-11 min 20C
The writer claims Delta 100 can be exposed at EI up to 250-320 ,Pan F at EI 125-160 and Delta 400 up to EI 800.
This suggests that it might be worthwhile to test W3 at higher dilution to see if it can give anything like these results.
I will get some Delta 100 and try W3 at 1+19.
Alan, you might also want to get some XTOL, which I would say gives a better reference point than D-76 with films such as Delta, when it comes to film speed/sharpness/graininess. It would also make a nice reference developer since it is based on dimezone-ascorbate (although that's where the similarities end). I've gotten even slightly higher speed from Delta 100 than XTOL, using DDX (all developed to normal contrast).
The formula you posted above from BJP really has zero sulfite? Depending on the type of emulsion, some solvent action can help maximize speed. One aspect of the BJP curves I find puzzling is that they appear to have the same B+F level. I find this hard to believe.
Last edited by Michael R 1974; 03-09-2014 at 01:52 PM. Click to view previous post history.
I used the densitometer on my Epson V700 scanner to try to match negatives as given by Delta 100 EI =100 developed 8min 20C in Xtol 1+0 , using diluted W3.
W3 1+29 developed 27 min 20C is close but still has slightly higher contrast and lower shadow density than Xtol 1+0.
So although it is speed increasing, W3 is inconvenient to use and not quite as speed increasing as Xtol.
How manufacturers managed to get a speed increase with developing times circa 10 min remains a mystery to me.
Kodak's formulators of XTOL wrote about it some years ago in an article titled "The genesis of XTOL". Try to get a copy of it. I believe at the time it was in Photo Techniques magazine. The combination of Dimezone-ascorbate, a relatively low, buffered pH of 8.2 (which also means no restrainer is required), and high sulfite content give it an almost unbeatable balance of sharpness, speed, strong toe contrast, and very fine grain.
Ilford's DDX gives similar results and even higher speed depending on the film (although perhaps with slightly less sharpness according to Ilford) - at developing times below 10 minutes. It is different than XTOL in formulation aside from its solvent nature (Dimezone-HQ, buffered Borax/Boric acid, pH ~8.5).
As I mentioned earlier, one potential speed-limiting aspect of W3 is the extremely low sulfite level at the working dilution (combined with high activity). Depending on the type of emulsion, some amount of solvent/etching effect can help increase speed by uncovering latent image centers in weakly exposed grains.