B&W reversal 1st and 2nd development strength

SalveSlog · Jul 25, 2024

1st development should give maximum contrast to reach clear highlights (possibly with help of some hypo) and is therefore very strong and long.
As far as I can understand, the 2nd development should do the same (without hypo) to give as high dmax as possible. The most easily developed silver halide is probably developed in the 1st development, leaving the less developable silver halide to the 2nd development.
Why then, are the recipes that I've read advising weaker/shorter 2nd development? Would it not be more logical that the 2nd development should be even stronger than the 1st?

Philippe-Georges · Jul 25, 2024

If you are talking about film reversal development, I would like to suggest the AGFA-Gevaert process, which you can see in the attachments.
Although initially intended for Dia-Direct, it works very good with Ilford's Delta 100 too (see: http://www.photoeil.be/books/dieter-roth.html)

PS: sorry for it is in Flemish/Dutch but some words and expressions are close to the Bokmål and/or Nynorsk.

Ivo Stunga · Jul 25, 2024

SalveSlog said:
As far as I can understand, the 2nd development should do the same (without hypo) to give as high dmax as possible. The most easily developed silver halide is probably developed in the 1st development, leaving the less developable silver halide to the 2nd development.
Why then, are the recipes that I've read advising weaker/shorter 2nd development (...)

I've done some eyeballing tests and just use the same developer for 2nd stage, with all the hypo in it and didn't find that to affect DMAX negatively (with the respective film+hypo combo), but it surely saves developer. And Foma does this too.
I go a step further - if I need my 1st stage longer, I make my 2nd stage longer accordingly.

Maybe the logic behind using weaker solution for shorter time is that after all the conversion beforehand, the remaining halides are readily available for conversion.

koraks · Jul 25, 2024

Ivo Stunga said:
Maybe the logic behind using weaker solution for shorter time is that after all the conversion beforehand, the remaining halides are readily available for conversion.

I'd expect so; since the fogging is complete after the reversal step, the remaining silver halide will be very readily/rapidly developable. It doesn't take much development to get the job done at that stage.

Ivo Stunga · Jul 25, 2024

Right.

I'll do this test right now with Delta 100, because that's a T-film and it uses relatively large amount of hypo compared to classic grain.
Let's see if that amount of hypo will reduce density at the second development stage.

I suspect not, because all is relative.

Philippe-Georges · Jul 25, 2024

It is known that tabular grain films are needing more fixer, that's why I prolonged by 1+1/2 the fixing time of the above mentioned process...

SalveSlog · Jul 28, 2024

I reverse developed medium format fp4+ and cut off a small piece from the end of the film 7 minutes into the 2nd development and removed the piece from the tank while continuing developing the rest of the film for 3 minutes more. I can't see any difference in density.

So I guess you are all right:
maximum density must be reached faster in 2nd development than in 1st.

I keep wanting to understand better why!

(I used no hypo)

koraks · Jul 28, 2024

SalveSlog said:
I keep wanting to understand better why!

As said, the silver halide in at that point is fully exposed/developable. To use a bit of a simplistic analogy: the developer doesn't have to search long and hard to find a developable center in each of the silver halide grains, but will bump into very quickly. As opposed to the original image-forming silver halide which only received a little exposure, creating a few developable centers here and there, the totally fogged silver halide in the second step has developable centers all over the place. So development proceeds quickly; the odds are more in favor of it, basically. This speeds things up massively. It's the same reason why during regular image development the highlights are the first to start coming on - if you've ever done development to inspection (e.g. on ortho film) you'll recognize it. You may also recognize in that case how you can tell if you over/underexposed by how quickly the image starts to come up. With prints it's also visible but the difference tends to be much less apparent because everything tends to happen a lot faster anyway.

SalveSlog · Jul 28, 2024

Thank you koraks, it's starting to dawn on me!

Ivo Stunga · Jul 28, 2024

SalveSlog said:
I can't see any difference in density.

And I can't see any difference in 1st dev being used for 2nd dev stage - with all the hypo in it. Therefore one can use one batch of it and save some developer.

My testing shows that one batch of PQ Universal 1+5 covers 2 films over a week with no development compensation needed - both stages and chems kept in glass bottles.

Philippe-Georges · Jul 28, 2024

SalveSlog said:
"...I keep wanting to understand better why!"

Perhaps the intensity (not only the duration) of the re-exposure?
In my Colenta, there was a cold-white TL tube buit in the cover that was very intensive.

And reed AGFA's instruction about that: two (!) 100Watt light bulbs on one meter distance for 4 minutes, that's a lot...

DeletedAcct1 · Jul 29, 2024

SalveSlog said:
1st development should give maximum contrast to reach clear highlights (possibly with help of some hypo) and is therefore very strong and long.
As far as I can understand, the 2nd development should do the same (without hypo) to give as high dmax as possible. The most easily developed silver halide is probably developed in the 1st development, leaving the less developable silver halide to the 2nd development.
Why then, are the recipes that I've read advising weaker/shorter 2nd development? Would it not be more logical that the 2nd development should be even stronger than the 1st?

What I've found is that if the first development step is carried too much further, a loss in DMax will result. To me it's not true that this step must be carried to completion.
The sensibility of the silver halide development centers (have I got it right?) is lost during the bleach phase and restored somewhat during the clearing step. I'm referring to permanganic acid bleach and metabisulfite clearing bath respectively.
So after the second exposure plenty of silver halide crystal development centers abound and a "normal" second developer can be used, even the first developer can be reused.
If however the slides are lacking in DMax don't panic: a final selenium toner bath can be beneficial.

Ivo Stunga · Jul 30, 2024

Alessandro Serrao said:
To me it's not true that this step must be carried to completion.

Makes sense to me, having pushed and pulled some slides here and there. It must be developed to your liking/need.

B&W reversal 1st and 2nd development strength

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B&W reversal 1st and 2nd development strength

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