Effect of rotary processing on acutance

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To what degree does rotary processing alter the edge effect of Black and White films. Is this change more noticable with T grain films as opposed to conventional films such as APX and FP4+. Are there any particular developers that maintain an edge effect even using rotary rocessors. Has anyone tried using a Jobo on the slowest rotation speed for B&W films.

Steve.

-- Steve Nicholls (gl1500@chariot.net.au), July 15, 2000

Answers

Response to Affect on acutance of rotary processing

Here's what Richard J. Henry says in the second edition of his CONTROLS IN BLACK AND WHITE PHOTOGRAPHY (page 214): "Since the edge effects occur because of lateral diffusion in the emulsion layer, the degree of agitation should have no effect on them and Barrows and Wolfe stated that agitation produced relatively little effect. Schwalberg disagrees, stating that violent agitation will completely eliminate these edge effects. I cannot agree since identical results were obtained on my machine mixer with very vigorous agitation, and inversion of the tank at 1-min intervals, and at 20 sec intervals."

I have an old article on Rodinal by Bob Schwalberg in which he recommends reducing agitation for greater acutance, but Henry's testing procedures were pretty solid so I suspect he's right. I believe he did most of his tests with D-76 and HC-110.

-- Ed Buffaloe (edbuffaloe@unblinkingeye.com), July 15, 2000.


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