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  #11  
Old 11th March 2021, 10:56 AM
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How do I know which stock developers make high contrast negatives, low contrast negatives good mid tone separation negatives? Surely almost any developer can be made to increase or decrease contrast by dilution, temperature, agitation or development time or a combination of any of the latter. I understand that some developers made up with pyro are said to be compensating developers but how can you tell what a developer will do from just looking at its formula?
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  #12  
Old 11th March 2021, 01:09 PM
Mike O'Pray Mike O'Pray is offline
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I agree that a lot of visual evidential content was missing such as examples of prints from each of his scenarios and what made things worse was that he gave no evidence of how much compensating developers could change a negative compared to non compensating.

I am not a "technical" person but how did he work out what constituted either kind of developer

However if I understood him correctly the bottom line seemed to be that you examined the scene and then decided which kind of a negative you needed to get you the print you needed for whatever you decided was right for that scene

Assuming this works in terms of choice of developer then isn't this the classic of one sheet of film at a time each one being developed in a tailor-made developer.

So unless you have LF or have say 3 135 film cameras and short bulk loaded cassettes or a med format with say 3 or 4 backs then the whole thing is nigh impossible without a massive waste of film ?


All of the above pre-supposes that what he has said works and now we are back to needing evidence which wasn't given

Mike
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  #13  
Old 11th March 2021, 01:35 PM
Terry S Terry S is offline
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Quote:
Originally Posted by Alan Clark View Post
For this reason I think it makes sense to begin by making test strips that home in on the mid tones. Not the highlights.

Alan
Even though I was in the darkroom yesterday, I found it hard to get my head around the authors explanations, but I too believe I do what Alan stated above. My way of printing has become second nature to me, but I can't relate the process to the way that the author describes it, at least in the small amount that I read.

Interestingly, I found this current article hard to read and gave up quickly, but I have followed and read other posts this person has made about Lith printing and Lith developer formulas, with no problem. I'm not quite sure what that says about the author and the way they write but also the way I am able to read easily some articles by the same author, but then struggle with other articles...?

Terry S
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Old 11th March 2021, 09:19 PM
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Well, yes, clearly you will need to adjust exposure time as you dial in more or less contrast from whichever end you are working, but my process is to decide on the contrast based on the highlight detail - get the highlights where I want them and then look at what the blacks are doing and adjust contrast from there.

I confess it never occurred to me to do it from the other side: starting at the shadows. That just seems counter-intuitive to me, but I'm sure that's just the result of doing it from the highlights for so long. I'll have to give it a try and see if my brain explodes from the shock

Cheers, Bob.
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Old 11th March 2021, 09:43 PM
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Originally Posted by Bob View Post
Well, yes, clearly you will need to adjust exposure time as you dial in more or less contrast from whichever end you are working, but my process is to decide on the contrast based on the highlight detail - get the highlights where I want them and then look at what the blacks are doing and adjust contrast from there.

I confess it never occurred to me to do it from the other side: starting at the shadows. That just seems counter-intuitive to me, but I'm sure that's just the result of doing it from the highlights for so long. I'll have to give it a try and see if my brain explodes from the shock

Cheers, Bob.
Why change the habit of a life time? Your brain exploding could be terminal and messy.😆
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  #16  
Old 12th March 2021, 08:45 AM
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> How do I know which stock developers make high contrast negatives, low contrast negatives ...

Developers usual contain three agents:
- the developing agent (e.g. Metol)
- a redox partner (e.g. HQ)
- an alkali (e.g. sodium carbonate, "washing soda")
- oxidation protection, usual sulfite

All developing agents work in alkaline environment. Their activity increases if the pH increases. That means, the contrast of the developer increases with stronger alkali.
weak alkali: sulfite alone, borate, baking soda (not stable)
medium alkali: washing soda
strong alkali: hydroxide

In reality, things are slightly more complicated because there is not an alkali alone but a buffering systeme.
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Old 12th March 2021, 02:50 PM
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Quote:
Originally Posted by Uwe Pilz View Post
> How do I know which stock developers make high contrast negatives, low contrast negatives ...

Developers usual contain three agents:
- the developing agent (e.g. Metol)
- a redox partner (e.g. HQ)
- an alkali (e.g. sodium carbonate, "washing soda")
- oxidation protection, usual sulfite

All developing agents work in alkaline environment. Their activity increases if the pH increases. That means, the contrast of the developer increases with stronger alkali.
weak alkali: sulfite alone, borate, baking soda (not stable)
medium alkali: washing soda
strong alkali: hydroxide

In reality, things are slightly more complicated because there is not an alkali alone but a buffering systeme.
If the ph of the developer is low, say ph 8 does that mean it will produce finer grain and a loss in film speed?
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  #18  
Old 12th March 2021, 03:36 PM
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Originally Posted by GoodOldNorm View Post
If the ph of the developer is low, say ph 8 does that mean it will produce finer grain and a loss in film speed?
I don't see a reason for a loss in film speed. But yes, you may expect finer grain. The reason is: What you see as grain are not the primary silver halide crystals but aggregates which grow from the reduced silver. This are more some kind of entangled "worms". These grow faster with more energy in the system.

Of course, the reducing agent play an important role. Rodinal has a pH of 11 or 12 (hydroxide-corbonate-buffer) but gives much finer grain than a typical paper developer, which is a Metol/HQ-washing soda type.
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