Azo and Amidol

This new article by Bob Herbst is available at http://unblinkingeye.com/Articles/Azo3/azo3.html. Herbst ran some tests at Dan Smith's request to see how the tonal range of Azo compared with that of platinum/palladium prints, using the test negatives he made for his article on The Effects of Pyro Stain (at http://unblinkingeye.com/Articles/Pyro/pyro.html).

Ed,
Thanks for bringing the article to our attention. among other things, it confirms the good points concerning the Michael Smith Amidol formula.

Having no experience with desitometry or step wedges and the like, a couple of elementry questions: does this indicate that D-76 offers better shadow separation and worse highlight separation than pyro? also it seems to say that pyro offers an ability to capture a longer brightness range (in the scene) than D-76. Do I interpet that right?

Also do you know what film Bob used? My experience with Berrger indicates it is fantastic with pyro but not so good with normal developers such as HC110 and XTOL. I never tried it with D-76 though...

Tom

Ed,

What kind of pyro does Bob use? And does it matter? As you know, Michael Smith is fanatical about ABC pyro, as fanatical as Gordon Hutchings is about PMK pyro. Which was used for the pyro step image he used?

Thanks!

dgh

Ed,

I'm not sure if this is true for others or not, but I am not able to access Bob's pyro stain effect page through the link you provided.

dgh

Very useful article, Ed. It quantifies the things that can be quantified, but acknowledges the fact that whatever the density range, Pt/Pd will still have a different look from Azo, because of the surface reflectivity, among other things.

Gordon Hutchings has come around and recently said that ABC is probably better for contact printing on Azo than PMK, because ABC produces a longer scale negative, and the grain masking effect of PMK is not so important for contact prints.

i had that problem too. go ahead and click on it and then when it tells you you cannot access look up at the address and delete the "close parathenses" and then try enter and that will let you in. Least it did for me.


lee\c

What happened with the link to the pyro article is that the close parenthesis became part of the URL. Here is the URL again: http://unblinkingeye.com/Articles/Pyro/pyro.html.

In response to Tom Duffy's question, I believe pyro offers better tonal separation at both ends of the tonal scale. This is particularly apparent when enlarging--see http://unblinkingeye.com/Articles/Pyro/Fig...4/figure_4.html --but is also evident to a lesser degree when printing with either platinum or Azo.

For these tests Herbst was using negatives developed in his own variant of the Wimberley WD2D formula. It all started with Herbst's article on the use of pyro negatives for platinum printing. He did a comparison that showed clearly that pyro negatives offered a longer printable tonal range for both platinum and silver. Dan Smith and I approached Herbst to run the same test on Azo, since Michael Smith had suggested (somewhere) that Azo might have a longer tonal scale than platinum. Herbst's results show that Azo has at least a nearly equivalent tonal scale, which is a very significant finding. --So much so that Herbst plans to use Azo and amidol for making fine prints in the future, in addition to his platinum work.

Herbst's article is a great one. My reading of it confirms that while platinum may show more steps than Azo (but just barely) Azo has a far longer visual scale. That must mean that the platinum steps are closer together, which helps give platinum prints the "flat" look they so often have. That combined with the significantly shorter density range of platinum prints supports my contention that prints on Azo have a longer scale than prints on platinum.

Bu some people do prefer the platinum look. Which paper you use should always be a function of how you want your prints to look rather than by the numbers.

Michael A. Smith

Just out of curiosity--and this will probably sound like heresy to people who prefer the classic platinum look--what happens if you try to increase the surface reflectivity of a platinum print? Will the emulsion adhere to any glossier papers, or what happens if you spray a high-gloss lacquer on a platinum print (okay, start preparing the stake for the heretics, but Strand varnished his prints, as I'm sure others did in that era)?

I wonder if this perception of scale has to do with the perception of silver particles floating on the top of the clear gelatin emulsion?

I think that platinum seems to favor an image with a certain type of tonal scale, perhaps that could be described as 'long midtones'. Azo/amidol seems to favor images with a prevelance of 'top notes'.
Sorry for the dogy terminology.. talking about photography is always difficult.

--Aaron