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Low contrast developer for P30

Apologies for the annoying / dismissive response. The "BTTB" thing gets to me for some odd reason.

The BTTB formula I've seen is a trivial / insignificant adjustment to Adams's version of divided D-23. The BTTB first bath is essentially a slight dilution of D-23 which doesn't make a difference. From a photographic perspective the altered concentration of metaborate in in the second bath also makes no difference. The Stoeckler version (and several others) also give the same sensitometry results.

Sorry again for the topic diversion versus suggested uses for two-solution development for this film.


Andrew O'Neill said:
Please elaborate.
Click to expand...
 
BT explained his variation:

Barry Thornton’s Writings - Geoffrey Billett Photography

FINE NEGATIVES, AUTOMATICALLY The clue to a fine monochrome negative is to give so much exposure as to give rich detail in the shadows, and so little development as to avoid highlights becoming too dense to print with subtle graduation. The vast majority of the negatives arriving in the Fine...
sannyassa.co.uk
 
By modifying the time in the first and second baths, it should be possible to get very similar results with AA and BTTB.

One criticism of these two bath developers, from a sensitometry perspective or otherwise, could be that there is no principled or wellfounded crtiterion for splitting the development between the two baths unlike a truly divided developer where all development happens only in the second bath.
 

There is though. With this type of two-bath (ie where bath A is a fully functioning developer), contrast is controlled by development time in bath A. That's about all there is to it. Bath B goes to completion/exhaustion but is not a control for contrast.

Some illustrations:

 
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Thanks, Milpool.
 
Thank you very much Milpool for sharing those HD curves! That is exactly what I would like to see for the long time.
What was time in Bath A? Was it constant or variable?
I'm surprised to see that same amount of borax and kodalk had basically the same effect.
From my experience, 4 min in B gives very different results from borax and kodalk.
In some other thread I mentioned that I tested only B development (in kodalk) after 5-6 rolls of film and I had decently developed film.
So, all that talk about carryover of A being neutralized/exhausted in B, is not right. It stays there and it's active.
 
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