</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (avandesande @ Jan 31 2003, 12:39 PM)</td></tr><tr><td id='QUOTE'>
Another thing that has become apparent from this article and the one on pyro stain, is that Pyro expands the scale of the highlights on the negative, which will in turn expand the scale on the print. This probably helps AZO achieve the long scale look, especially in the highlights. </td></tr></table><span class='postcolor'>
Sensitometrically speaking that is incorrect Aaron, and is very well explained in Dr. Henry&#39;s book, "controls in black and white". You cannot expand the paper scale, all you can do is fit the negative to the paper range. As Bob explained in his article azo is just better able to accomodate a more contrasty negative than most silver papers. I am not sure that the same cannot be said for other developers which can separate the highlights as well. Azo has a very long scale while pt/pd compresses the scale, this is why very contrasty negatives are used in pt/pd to make up for this compression. The key is to fit the negative to the paper. If anything your statement is better applied to pt/pd than to azo. Although pt/pd is "cramming" more tones in a much shorter scale, it&#39;s ability to better differentiate the highlights gives it that "long scale" look which is really not there.

In this case the "hard" data is very misleading, although on a step tablet pt/pd is able to accomodate 9 stops, the reality is that many of those stops are a morass of ugly looking blacks. Although the "data" might suggest the greater ability of pt/pd to fit more tones to the paper the reality is one where many of those are just plain ugly and useless, if anything I would say that azo truly fits the stops printed on the step tablet which are useful.

I am not "defending" pt/pd, but I have to say with all due respect to Dan Smith and Ed Buffaloe, both of whom are persons I respect very much, that I thought this article was a little bit of "fluff". It is impossible to quantify perception by printing step tables and IMO to write an article comparing this mediums is similar to writing an article comparing blondes and brunettes....