In Herbst's tests platinum reproduces 19 steps of the step tablet in a manner that is clearly discernable to the human eye, while Azo reproduces 18. However, the density of the platinum print extends from 0.13 to 1.47 (reflective density range 1.34), whereas the Azo density extends from 0.15 to 1.92 (reflective density range 1.77). The tonal range reproduced is virtually identical, but the reflective range of the Azo is just over two stops greater than the platinum print in this test. The extended reflective range of the Azo is in the blacks, which are much deeper than the blacks in platinum/palladium. However, the high values of the platinum/palladium print have more delicate gradation than the Azo print.
Hmmmm...I don't see why this is any surprise. I have only been printing with pt/pd for a few months and it is clear to me the tonal range is compressed. As a matter of fact it is clearly explained in the Arentz book. The platinum particles are in the paper and as such they "trap" light thus the lower reflectivity. The "flat" prints Michael mention are mainly due to a poor choice of negative rather than the inability of pt/pd to produce luminous prints. Terry King made a comparison of black from a pt.pd print and a silver print and most people thought the pt/pd had "deeper" blacks than the silver print, even thought the D max is only 1.4.
IMO pt/pd is better for high key negatives where the light tones are more important than the shadows, while azo I suspect is better for negatives with a long tonal scale and lots of "grays" where the dark and light tones are used for accent rather than an integral part of the "message".
The prints are very different and should be used for the particular "style" of the photographer. Trying to compare Azo to pt/pd is like comparing apples and oranges, each have their own taste and qualities. To say that either one is "better" or capable of yielding better prints than the other I think is foolish.
I applaud Bob's open mindedness but I really think this was more an exercise in sensitometry than a comparison. What is next? Azo vs POP, or Pt/pd vs Kallitype?
Jorge, it is almost impossible to do a completely 'fair' comparison, I am a just greatful that someone is trying to make some sense of what to this point has been borne out by experience and word of mouth.
Most people will agree that a master of their medium will pick subjects and conditions that suit their process. Not many negatives print equally well on platinum and AZO.
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.
I think it is always useful to have hard data rather than someone's subjective impression. I love the look of platinum/palladium, and there are certain subjects for which it is the perfect medium. The same is true for Azo.
In regard to the D-max of platinum, there was a recent post on the Bostick & Sullivan forum regarding Mars All-Purpose Translucent Vellum paper. It is said to have excellent wet strength and to give significantly better blacks than other papers. There was speculation that the deep blacks are due to its translucent nature, which allows light to penetrate into the depths of the paper.
</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (edbuffaloe @ Jan 31 2003, 11:07 AM)</td></tr><tr><td id='QUOTE'>I think it is always useful to have hard data rather than someone's subjective impression. I love the look of platinum/palladium, and there are certain subjects for which it is the perfect medium. The same is true for Azo.
In regard to the D-max of platinum, there was a recent post on the Bostick & Sullivan forum regarding Mars All-Purpose Translucent Vellum paper. It is said to have excellent wet strength and to give significantly better blacks than other papers. There was speculation that the deep blacks are due to its translucent nature, which allows light to penetrate into the depths of the paper.</td></tr></table><span class='postcolor'>
I was the one who started the Mars Vellum discussion on the B&S board. After many years of printing platinum I found a paper that happens to produce a startling black. Doesn't mean it's better or worse than the many other papers I use, just different. What's even more exciting about this paper for me are it's ultra-smooth tones, excellent resolution of fine details, and fantastic tonal separation. I don't own a densitometer, so I can't tell you what the reflection density is, but my guess is that it approaches or surpasses the DMax of matt silver gelatin papers. My opinion is that this super deep black comes from a combination of factors: the transluscency of the material, the ultra smooth surface, and the fact that the sensitizer seems to sit way up on top of the paper rather than being absorbed deeper into the fibers that typically happens with more "normal" papers used for platinum.
I agree in general with Jorge that the sensitometric comparison of AZO and platinum is little more than interesting trivia. What is more important to me is how the medium conveys the image and intent of the photographer. I've done lots of printing on AZO with Amidol and Ansco 130 (I still have a few boxes of 14x17 doubleweight AZO in my darkroom). I've also done and continue to do a lot of printing with Centennial POP. My main medium for the last 10+ years has been platinum/palladium. In the last couple of years I've also been adding layers of gum bichromate over platinum for the unique look that those combined processes provide. Through all this printing I have purposely avoided the use of a densitometer because, *for me* that type of analysis is simply a distraction to my main intent which is making really beautiful prints. All of these materials are capable of wonderful results when coupled with the right image and a well-made negative. My preference is for very warm tones and lots of color, so I am much more attracted to platinum, gum over platinum and POP than AZO. Nothing makes me yawn faster than a neutral gray print.
Regarding the question of increasing the surface reflectivity of a platinum print. Strand did it and it is still common practice. I've used wax and acrylic gloss medium to achieve this effect. I've also read of people using Future Floor polish for the same purpose(!) For some papers these treatments make a dramatic change in the appearance of the blacks. As far as getting the sensitizer to stick to a glossier surface, that is a much more difficult problem.
</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'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'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....
I am referring to expanding the scale of the negative. If you look at this article,
you will see that the scale of the highlights are exaggerated by pyro. This compenstes for the smaller scale of the silver paper highlights. The highlight seperation effect of pyro is well documented in the literature. Look at the picture of the lightbulb in Ansel Adam's 'The Negative'
I did read the article, and the effect of highlight separation by pyro although well documented is still a matter of perception. Nobody has proven conlusively that pyro does "better" than any other developer when used appropriately.
If anything again pyro is more effective with pt/pd as it blocks more UV light as explained in the article you mentioned. Arentz and Herbst have done this study where pyro is compared to a "normal" developer and it was concluded that a normal developer is just as capable of producing the same results. As I stated you have to fit the negative to the curve and the pyro stain does not make the paper "better", azo is simply better able to accomodate the separation by its own nature, not because of the pyro negative. IOW if you have a highlight that is 1.87 and another that is 1.9 azo would be able to separate them as shown in the article, but if you have a 1.9 and a 2.0 highlight no matter what you use, pyro, d76 or anything else, the 2.0 would still show as paper white. The fact that the pyro stain can better diferentiate between closer densities does not improve the paper. The paper is only showing what it can do, no more no less, no matter what developer has been used. I would say that the tonal scale of azo is actually relying more on the paper developer used than on the negative. I think Michael has proven this, azo in any other paper developer is just another silver paper, amidol is what lends it the better reproduction qualities.
From my experience in printing in silver I can tell you that given a negative that contains the same reproduction scale of the paper, all the tones will show in the paper. Reproduction is dependant on the paper, not the negative.
This is the problem of doing step tablet tests for something as subjective as photographs. Which reminds me if you go back and look at the azo article you will see that the print reflective density range is exactly the same for both the pyro and the d 76 negatives, this cannot be unless you have some give somewhere, the d 76 neg appears to have better separation in the dark tones. I am sure given a little bit of more work the d 76 negative could have shown better separation in the highlights also.
Part of the problem with this discussion is that meaningless terms like 'tonal range' and 'tonal scale' are being thrown around as if they had some sort of quantifiable meaning. Jorge is exactly right in his previous posts. The differences between the processes have to do with the reflective density difference between platinum and silver gelatin. Azo/Amidol does not have a greater reflective density difference than any other glossy finish silver gelatin paper. Dmax for all of these range from 1.9-(2.1 in some cases.)
Because of the matte finish that handcoated platinum prints have by necessity, the maximum reflective density is anywhere from 1.3-1.5
(In a *well made* print. As an aside, you will see many basically crappy platinum prints floating around made by some photographers that have some serious technical problems in basic technique. Do not assume you know what a good platinum prints looks like until you have seen one done by a Kerik, a Dick Arentz, a Stan Klimek, or a Stuart Melvin. )
But back to the reflective density thing. If you get a silver gelatin paper with a ^matte^ finish, guess what? The maximum reflective density of a maximum black is about 1.5 - same as platinum/palladium. As Dick Arentz points out by way of Minor White, what really matters is the 'convincing' black. If the paper is delivering a reflective density that appears maximally black to the viewer, he or she won't give a rat's ass whether the Dmax is 1.5 or 1.9. The thing that makes a print 'sing' ,or not, is the gradation between the infinite steps of tone (yes, more than 256, you photoshop users), and how this gradation reflects the actual brightness differences that were present in the original scene.
If you print (with good technique, again) a step wedge on Azo and a step wedge on platinum/palladium, and plot the results, you will notice that the high negative densities on platinum/palladium stretch out into a very long toe. The highlight gradation is very delicate. At the other end of the plotted curve, you will immediately see that the shadow values are also somewhat compressed and have a lower slope (e.g. lower contrast) than the relatively straight line area between ^print^ zones 7 and 4.
The Azo wedge will show an amazingly straight line response, with very little toe and shoulder on the curve. I've done this exercise, and its interesting. Azo/Amidol is strikingly different than Azo/Dektol in its curve shape. The point that Jorge makes is relevant, though: Just because platinum and Azo/Amidol require a density range of 1.4 to completely 'fill up' the print density range just means that you have to have more contrast in the negative to begin with. If you choose to use a process that has a print exposure scale of 1.0 to completely fill up the reflective density range of the print, you can tailor your negative exposure and development to give you just that result.
What does all this mean? I think it means we are technologically capable of producing stunning prints using either process. It just depends on what 'look' you like. Give me the process, and the real life reflective values you want to capture on the final print, and I can make you a negative that will fit the process. It also means that we have the technology at our fingertips to produce trivial, shoddy dreck. Taste, discrimination, and esthetic sensibility will go a heck of lot further than chemistry in producing a fine print. Understanding how the process behaves is only useful if you have a real vision of what you want to achieve.
This whole thing is similar to an argument over "which is better, red wine or white wine?" Believe me, there are some crappy wines of both types, and it seems like it might be more relevant to discuss "which is a better white wine" or "which is a better red wine". And don't ask somebody who hates sweet white wines to give you useful assessment of a bottle of Chateau D'Yquem, or conversely, ask a red wine hater to give you any useful information on bottle of Lafite Rothschild. And my red/white wine analogy is good, I think, in that there are some people who like one or the other, and some lucky souls who can taste and appreciate both.
So drink up and go make some art.