I am not a chemist and there is plenty I don't understand. It
may be that the "optimum" is in the proportions and not the
absolute amount.
Also, the performance of the developer as far as grain is NOT
the same. Diluted D-76 is slightly grainier. If one looks at
Microdol-X or Perceptol, the super fine grain performance
definitely changes with dilution. At 1:3, for instance, these
developers become high acutance developers and deliver full ISO
speeds with grain similar to D-76. It is only at full strength
that they are extra-fine-grain and deliver about half the ISO
speed. Is this due to the concentration of sulfite or something
else? I don't know. In some cases developers become finer grained
with dilution.
EVidently, what ever Ryuji discovered about the optimum
concentration of sulfite was discovered by others long ago. He
often made statements without expanding on them.
The 1929 paper on D-76, which introduces the buffered
version, shows a number of variations including one without
hydroquinone but does not explore the variation in sulfite
concentration. D-76 was originally introduced as a fine grain
developer for a then new Kodak duplicating film for motion
picture negatives. It rapidly became the standard developer for
camera negatives but its instability was discovered. Kodak Labs
then endeavored to discover why the activity was unstable and the
buffered formula was one result.
I will have to look in my archive to find the citation to the
research paper. My memory was once good enough to have this stuff
at my beck and call but no more.
On 3/24/2021 7:03 PM, John Stockdale wrote:
About the optimum amount of sodium sulfite/Litre:
There are quite a few versions of similar developers with 80g or 85g sodium sulfite, such as the Agfa version mentioned by Richard below, also Adox Borax MQ and Ilford ID-78 ("Microphen" reputedly, though that has phenidone instead of metol).
But the moment you dilute 1+1, in order to optimize your results, you're a long way from 100g or 80g of course. Maybe 50g is some sort of optimum?
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On 25/03/2021 11:12 am, `Richard Knoppow wrote:
I can understand the grain, its an active developer but the fog has me fogged.============================================================================================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.
Back in the bad old days film took a lot longer to develop than it does now. I don't completely understand why. D-76 used to take 10 to fifteen minutes for most films. Now its too fast unless diluted. DK-50 should be diluted 1:1. Still a rather fast developer. It can be replenished when diluted unlike some other developers.
I typically use D-76 diluted 1:1 as a one shot. There may be some increase in grain from diluting but I've never noticed it. Kodak does not give times for dilution of 1:3 but Ilford does for ID-11. I've tried it and don't like it. It becomes an acutance developer with, to my eye, a rather unpleasant look. Strictly one shot at that dilution.
Ryuji Suzuki wrote long ago that he thought the optimum formula for D-76 was to use 85 grams of sulfite per liter, he did not say why. I found that AGFA used that amount in their version of D-76. Not sure it makes any real difference in result but worth trying if you mix your own.
I think if I start shooting sheet film again I will try DK-50.
On 3/24/2021 3:39 PM, Tim Daneliuk (Redacted sender tundra for DMARC) wrote:On 3/24/21 3:54 PM, `Richard Knoppow wrote:=============================================================================================================
Some care must be taken about terms; base plus fog means the density of the support or base plus fog.
In my experience, the same film processed in DK-50 had lower FB+F than with other
developers, at the expense of a slight increase in grain.
WB6KBL
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