film ecthing ?

MVNelson · Feb 3, 2007

I hate to beat a dead horse to death but once and for all... Is the type of film emulsion ecthing I get when developing say TMY in pycocat-mc related to (what has been thoroughly discussed here numerous times) adjacency effect and edge effect. The ecthing is most pronounce on negatives that are sharply focused and have sharply rendered subject matter. The reason I ask, If I am getting such rather pronounced ecthing using TMY/pyrocat-mc (slow wobbly log-rolling BTZS tubes) should expect to get even more pronounced etching and or edge effect with the minimal or lesser aggitation schemes. I suppose I'll do the test but if I'm there I'm there.... if you know what I mean .

gainer · Feb 3, 2007

What looks like etching is in fact hardening with consequent shrinking of the emulsion in proportion to image density. The differential refraction due to this shrinking has some effect on sharpness. It is more due to the developing agent(s) than to the method of agitation. Pyrogallol is well known for this effect. It is possible with proper combinations of film and developer to wash off the softer parts of the emulsion to make a matrix that can be used as a printing plate to make prints with ink.

Catechol, hydroquinone and many other agents have this characteristic to some degree or another.

MVNelson · Feb 3, 2007

Yes, I appreciate that part of the answer. I actually have used matrix film and pyro developer to produce Dye transfer prints for some time using that principle. What I am not sure of is if the emulsion ecthing related to or the same as the edge effects that seem to have endeared the proponents of stand or semi stand etc developement ? Thanks for your comment.

Miles

Markok765 · Feb 3, 2007

I find my rodinal stand developed neg etched sometimes, and sometimes not. Etching is quite amazing on Kodachrome.

-Marko

gainer · Feb 3, 2007

Pyrocat MC seems to have somewhat more etching than the other members of the family, which I think may be due to the fact that catechol, ascorbic acid and metol all have more than average tanning power. Again, I think that if you used Pyrocat MC to develope negatives of the same scene to the same average density by both agitated and stand or semi stand methods you would see little or no difference in the tanning effect.

MVNelson · Feb 5, 2007

Thanks for your comments. 4x5 tmy in pyrocat-mc 1:1:100 in BTZS tubes has become my all time favorite combo. What I get in the prints is high accutance , apperent sharpness and a bit of "3d-iality" that I have grone to love. I was just wondering if this is what folks are describing as edge effect ?

Miles

gainer · Feb 6, 2007

There can be "edge effect" without etching, but it there not likely to be etching without edge effect. One cause of edge effect is the bromide generated in the higher density spreading to the lower density area and making it even lower in density. Sometimes it is an optical illusion, as you can test by placing a black knife edge over a light gray area. You may see the gray as lighter adjacent to the black. This illusion will change with viewing distance and will disappear if you get close enough, say with a magnifying glass. If the black on white edges in your photo are showing this effect, be sure to check with a magnifier to see if it is in fact an illusion.

film ecthing ?

MVNelson

gainer

MVNelson

Markok765

gainer

MVNelson

gainer

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