Just one correction of a typo in one of my "questions" (which Mr. Bill has already tried to answer) in case it caused any confusion:
"Why would the developing time for AH-15 be longer shorter than for AH-1 if the only difference between the two developers is a lower Metol concentration?"
Obviously it should have read "Why would the developing time for AH-15 be shorter than for AH-1..."
Michael, PE already answered that question: Metol is a salt from a secondary amine and sulfate, which makes it quite acidic. This means that the dev with more Metol will be lower in pH and less active as a result.
Trying to be the best of whatever I am, even if what I am is no good.
Yes sorry about repeating the question - I was just highlighting the fact there was a typo in the original question. PE and Mr. Bill understood what I meant regardless of the typo but just in case there are others interested I didn't want the typo to cause any confusion.
See my post of microdensitometry. X-Rays are sharper as there is no reflection in the coating, but white light is reflected off grains. There is quite a bit of turbidity in coatings wrt visible light. Look at film. Can you see through it? There are dyes there to reduce internal reflections. If you look at a pure film emulsion, it looks like yellow milk.
Thanks for the correction. My bad. See the actual units in the post showing the traces read in my post on edge effects. It is marked micro meters. I hastily used mm instead of um or looking up the Greek "mu".
Sorry and thanks for the heads up. I thought it was a question about X-ray vs visible light.
According to these data, it's impossible to improve the acutance of the (old) Tri-X.
For this film, AH-2 is (was) the best compromise for a very moderate gain in speed and indiscernable loss in granularity.
Last edited by Harold33; 12-20-2012 at 07:10 PM. Click to view previous post history.
Harold - It would seem to be the case but only within the confines of this particular experiment with these particular developers - and only in comparison to D-76. But one could almost certainly formulate an acutance developer that would have produced higher acutance. Perhaps a Crawley-type Metol-Carbonate or similar developer for example. Or a different developing agent. The developers in this experiment were all based on Beutler. And remember Altman and Henn were trying specifically to evaluate the effects of the Metol concentration and sulfite concentration.
Regarding the agitation method used during processing:
Michael had asked about this in his pdf, my reply, per the paper, was "Processing was in the sensitometric machine of Jones, Russell, and Beacham (Jour. SMPE, 28:73 (1937) which gives strong and uniform agitation."
The first SPSE Handbook of Photographic Science and Engineering (Woodlief) has a short bit on "sensitometric processing apparatue." One of the systems has the same reference as above (Jones et al), and is characterized as: Type of agitation = paddle, cost = high, and features = Suitable for high-volume high-precision work; holds up to 60 film strips; adapted to automatic sequencing.
So we know 1) it is not the well-known (?) ANSI processing method used for negative film speed testing, and 2) the cost would be out of range for most enthusiasts.