That is often the case, but it is interesting to discover the truth on one’s own.Originally Posted by Bruce Watson
As I mentioned earlier, I have done no specific testing as of yet. When I began scanning large format negatives I was so excited with the ability to apply tonal corrections and clean them up in Photoshop, and so pleased with the outcome in printing from digital negatives, it never crossed my mind to interrupt the fun to actually test what was happening.
However, I have speculated on three areas of image quality that I consider germane to what further testing may reveal. Those areas are grain, apparent sharpness, and resolution.
Grain – If one develops their negatives exclusively for scanning it makes sense to develop them to a relatively low CI. This minimizes grain and also maximizes resolution. In this circumstance, I personally do not believe that staining developers will offer any advantage over a good non-staining formula such as Xtol. However, if negatives are developed to relatively high CI for printing on AZO or alternative processes there may well be and advantage to the staining developers. How much advantage will depend on format and amount of magnification?
Apparent sharpness – Apparent sharpness depends on both resolution and edge effects, but primarily the later. Most of the popular Pyro staining formulas are high acutance developers because they enhance edge or adjacency effects. Scanning can not capture this effect of the film because the edge effect lines, some as small as 1 micron in width, are simply too narrow to be captured by most scanners, even high quality drum scanners. To do so I calculate that one would need a scanner with resolution of about 10,000 spi with yield of at least 80%. I don’t have that kind of scanner.
Resolution – Most of the scientific literature on developing indicates that resolution is a quality of films and is not much affected by developer, and Dr. Richard Henry reached the same conclusion after extensive testing of his own. But, it turns out that staining developers were not used, at least they were not in Dr. Henry’s testing or in any of the literature I have reviewed. So, I recently tested this myself, using a USAF chrome on glass resolution target with maximum resolution of 225 lppm. I tested two staining developers and two non-staining developers. Guess what. It turns out that the staining developers gave slightly better resolution with every film and in every single test. The difference was not great, say for a given film like Delta 100 we get about 90-100 lppm with the staining developers, and 75-85 with the non-staining developer. Is this difference significant? Well, potentially it could be, depending on the capability of your scanner and the amount of magnification of the final print. Obviously, the weakest link in any imaging system determines final image quality, so if your scanner has a maximum potential of 50 lppm, which is in fact very, very good, there is no way to take advantage of 100 lppm on the film. So let us say, on this point it depends, but regardless, I definitely found some advantage in the staining developers for resolution. BTW, the developers tested were PMK and Pyrocat-HD, which gave about equal resolution in every test, and D76 1:1 and Xtol 1:2, which also tested about the same.
Sandy King
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