B&W reversal dmax

SalveSlog

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I reversed Foma Ortho this way:

1st dev:
Fomadon LQR 1+10 distilled water (no silver solvent added)
12 minutes

Wash

Bleach:
Potassium Permanganate (2g/L)
mixed 1/1 with
Sodium Bisulfate (50g/L)
5 minutes

Wash

Clearing:
Potassium Metabisulfite (25g/L)
2 minutes

Wash

Fogging under light bulb 4-5 minutes

2nd dev:
reusing 1st dev
8 minutes

Wash
Fix
Wash


Before developing the film (medium format), I cut off a piece from one end and light-fogged it. Then put it through the 1st dev and fixed it.

After developing the film as described above, I compared that piece with the other end of the film, that had gone through the full process. Putting the two pieces on the light table and pointing my light meter through each, the one that went through the full process, lets 2,5 stops more light through.

More precisely: Measuring with my light meter directly to my light table, I read EV 14. Through the piece of film that only went through 1st development I read EV 8,5. Through the final part of the film (from where it was unexposed in the camera) it reads EV 6.

I seem to have lost a lot of the films potential dmax during my processing. When and where did that silver go?
 

DeletedAcct1

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Too much time spent in the first developer (trying to compensate the absence of a silver halide solvent to get clear highlights) means more fog, more fog means more silver dissolved in the bleach, more silver dissolved in the bleach means less final DMax. Plus a maybe too strong final fixer bath.
Imho.
Plus: the maximum density a film can attain in a normal b&w negative process is not numerically equal to the maximum density a film can attain in a reversal context.
You can "regain" some lost DMax with a final selenium toning bath.
 
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Anon Ymous

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According to this, the reversal processed film is denser by about 2,5 stops and has a total density of ~2,4. Accounting for a base density of 0,3, we get a Dmax of ~2,1. Not too bad, but could be better.

But perhaps it's the other way around?
 
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SalveSlog

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You are right AY, it was the other way around.

The reading for the reversed film was EV 8,5 and for the piece of the film that only went through the first development was EV 6.
 
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SalveSlog

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I now scratch my head to find a strategy to find the optimal amount of silver solvent for a specific film without having to go through the full process. I'm quite sure most of you have a brighter head than I ... maybe there is no such strategy?
 

Ivo Stunga

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A lot can be deduced in the reexposure stage and I don't see how you could arrive at a hypo value for film X without evaluating completely processed and dried film. Impossible imho as bleach and fix have their effects on dmax.

My method is to take film X, shoot it at box speed and do traditional 12min first dev without hypo added. If overdeveloped, I just step back a minute or two, if undercooked, I add some hypo and do 12min again and go from there accordingly until highlights are clear.

When that's nailed, you can fine-tune your dmax by adjusting time+hypo
 

Ivo Stunga

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To save film in this fine-tuning process I just cut my 135/36 roll in three strips and put the time and effort in to have 3 different development iterations.
 
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SalveSlog

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This was the first time i tried to check dmax with my meter through the film. It made me feel like a fool thinking about all the films I've already developed - stubborn as I am: with no hypo and acting happy.

But then I checked a recently reversed FP4+ and the lightmeter says EV3.5 for the darkest part of the film! Which I think is dmax close to 3.2 and not so bad at all? That films 1st developer was PQ Universal 1+5 for 12 minutes with no hypo.

So now I'm a little less shameful again but quite confused!!

(I'm sure the highlights could be clearer etc., but the film expired in 2021 and is heavily affected by the backing paper problem. So that is a bit difficult to estimate.)
 

Ivo Stunga

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SalveSlog said:
quite confused!!
Click to expand...
Don't be, it's all film dependent. Some films need tiny amounts (if any), some need quite an amount - like Delta 100 and other T films.

I like Adox HR-50/Scala 50 (same film, originates from Aviphot 80) and they require 0,1g and 10min 1st dev to my liking, box speed.
I like some Delta 100 too and it requires about 4g!

If you'd process HR-50/Scala 50 with 4 grams of hypo added to 1st developer, you'll get very thin positives, if at all - can't be saved.
If you'd process Delta 100 with 0,1g, you'll have unusable, ridiculously dense slides that can be saved somewhat by bleaching in very dilute bleach > clear > redev (needed?) > fix.
 
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DeletedAcct1

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The quantity of a silver halide solvent depends on the nature of it (DTOD, thiocyanate, thiosulfate), the presence of a developer accelerator (PEGs - polyethylenglycoles), the thickness of the emulsion, the quantity of Ag in the emulsion, and the type of gelatine.

It's obvious that, as Ivo has stated very well, the silver halide solvent quantity can be only found by trial and error.
He has mastered this art of b&w reversal.

May I add a new product that can be of interest: Adox EMH-1 emulsion hardener https://www.fotoimpex.com/chemistry/adox-emh-1-emulsion-hardener-100-ml-conc.html
Usually it's not the emulsion that fails under the permanganate bleach, but the subbing layer, the adhesive layer between the base and the emulsion. However this product (which I don't know what is made of - probably glutaraldehyde) I feel can be beneficial in some instances.
 
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Ivo Stunga

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Alessandro Serrao said:
It's obvious that, as Ivo has stated very well, the silver halide solvent quantity can be only found by trial and error.
He has mastered this art of b&w reversal.
Click to expand...
Now that's a strong statement and I'll take it as a proof that simple observation, healthy dose of experimentation and skepticism (of what's written online as possible or not (DR5)), note keeping and variable isolation with the element of purposefully over/under doing to see what happens - will get you far even with little to zero understanding of chemicals involved.

It's an art of trial and error. Like Hideo Kojima videogames - fail hard and many times, don't give up and push ahead with patience and open mind - to find a solution for epic outcome
 
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