Tuesday, February 12, 2002, 11:55:26 PM, Shel wrote: SB> Please repost. I may have missed it.
I don't know if it makes enough sense, but see for yourself :) ... *** Hi Shel, I am no expert :( but this is what I think about it. Of course, there is much hype (not hypo <g>) and legends in photography, so it indeed might be all hypo :) New emulsions use monosized crystals. These would have no tonality at all though, so they have to combine at least two (D3200 has 4 or 5 IIRC) layers to get nice tonality. Why? Remember, sensitivity of silver grain is proportional to its size (or more precisely, area exposed to light). Silver grain doesn't register tones, it just is "on" or "off". Monosized grain layer has same sensitivity all over, so ideally, would register only black or white, and produce a half-tone screen (is evenly spaced, it would be very similar to halftone screens used in printing biz). Actually, the screen is more stochastic. Tones in B&W are mostly from different sensitivities of grains, that's different sizes of grains. In monosized modern emulsions, they combine several layers of different sensitivity to achieve better tonality. In "older" emulsion, there are many different sizes of grains mixed together, thus many grains of different sensitivities mixed together. Some people say that the old type films are better for many subjects like portraiture because they can distinguish more shades of gray in small exposure differences than modern films. Whether this is true or not I do not know, there are so many variables and personal views in B&W that I just try something and if it works well I like it. But I have indeed seen some classical film prints which had great tonality, comparing favorably to tonality of contact printing LF. What makes it even more difficult is that apparently, HP5+, FP4+, TX, PX and similar are all thin-emulsion "wonderfilms" introduced in their modern form in 70-80, having much thinner emulsion thus being quite sharper than the older thick emulsion films. Some people say because of this thinner emulsion, there is less mixed grainsizes, so tonality suffers in the thin-emulsion films. This might all be bullshit for all I know of the technical side of things, but I have seen 35mm prints from classical type film developed with good old Rodinal, which indeed had exquisite tonality. All this makes sense to me, but like in everything scientific, making sense and being true can be different things (or not). *** Perhaps some chemist can shed some actinic light to it :) ? Good light, Frantisek Vlcek - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
