Does Agitation Affect Tonal Seperation?

Ian-Barber

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According to the text book, Exposure affects shadow information, Development affects highlight information.

Would the amount, or frequency of the agitation affect tonal separation on the straight line.?
 

Ian Grant

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Some say it does, it will affect local exhaustion which is why some use minimal agitation and it also affects the overall level/speed of development. It's better to be consistent in your agitation as that aids predictability.

Ian
 

Ian-Barber

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Some say it does, it will affect local exhaustion which is why some use minimal agitation and it also affects the overall level/speed of development. It's better to be consistent in your agitation as that aids predictability.

Ian
I am just trying to get an understanding of what is actually happening to the film during the development stage, things such as, what would happen if I didn't agitate, what would happen if I treat it like a cocktail shaker, what would happen if I only agitated slowly etc etc
 

David M

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#4
Highlight and shadow are convenient shorthand for the effect of development. The whole film is affected proportionally, including the midtones. How could it be otherwise? The precise effect will depend on the actual materials used but Ian will know more (probably much more). This is something that has baffled beginners who have only read about the Zone system.
I've seen someone who cocktail-shook the tank and it worked perfectly well with her times, but she was advised that there was a danger of stripping the film off the spirals. I didn't see that happen.
Slow agitation on spirals (or other holders, I presume) means that the part of the film held next to the spiral gets a little river of developer running along it, clinging by surface tension, as you turn the tank, which counts as extra agitation and overdevelops the edge. I can't comment on rotary processing, but I assume that Jobo, et al have done their homework.
Developing in trays is another matter. Very slow agitation of the stack would give blotchy development. I don't see how you could do fast agitation.
 

Ian Grant

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Watch how a print develops, maybe use the developer more dilute so the dev time increases. Provided it's submerged it will develop OK with next to no agitation, slightly faster with continuous agitation.

With film as long as the developer is at a reasonable strength you'll see little difference between say 2 inversion agitations of a tank per minute to almost none, however increase the agitation and you increase development.

However if you use more dilution then agitation becomes more critical, lack of it leads to localised exhaustion on the micro level which increases edge effects.

Ian
 

Ian-Barber

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However if you use more dilution then agitation becomes more critical, lack of it leads to localised exhaustion on the micro level which increases edge effects.
If I am not mistaken, this is the premise of the EMA system which Steve Sherman Promotes
 

Ian Grant

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If I am not mistaken, this is the premise of the EMA system which Steve Sherman Promotes
It is, the technique is quite old works well with Rodinal. I've always found that the edge effects with Rodinal and now Pyrocat HD are sufficient without going to the extremes Steve uses.

Ian
 

Alan Clark

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Ian, if you want to get edge-effects with Pyrocat HD you may be better using unequal amounts of A and B and a higher dilution. Try 1+1.5+200 and something like agitation once every 10 minutes for 40 minutes. Sandy King's advice, not mine.

Alan
 

Alan Clark

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That was the advice he gave for FP4+.

I couldn't get any edge effects when I tried it, but you may have more luck. I sense that you have the bit more firmly grasped in your teeth than I did. I only tried it once...

alan
 

Ian Grant

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#12
You get edge effects in many developers, however Pyrocat HD is an acutance developer and they tend to be slightly stronger partly due to the tanning effects of the Pyrocatechin.

With a 5x4 negative printed to 20x16 or larger you should see increased sharpness fine detail compared to full stregth D76/ID-11. It'll be less noticeable with smaller prints.

Sandy King was mainly a ULF photographer and making contact prints, he's shooting more MF I think these days. Many like to icrease and exaggerate the edge effects when contact printing.

Ian
 
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