My experience with BW, which is considerable, suggests that the differences between films are mainly in grain, speed, dynamic range and different degrees of tonal separation at various points in the range. The all seem to translate color in a nearly identical fashion. The PhotoShop grayscale conversion is factored to translate color the way BW film does without filtration. In regard to discussions of conversion recipes on the list, most have been in regard to street photography and people shots. Filtration is rare in that type of photography. As I said in a previous post, I can see the advantages of color channel manipulation in landscape photography. But for street portraiture, it appears to be unnecessary, and in some cases, counterproductive. The grayscale conversion renders color very close to the way film renders color. The initial RAW conversion allows control of the range. A curves adjustment after a BW conversion provides a level of control over midrange contrast th! at is very much in keeping with one could do with exposure, development and paper choice, were one working with film.
> Paul Stenquist <[EMAIL PROTECTED]> wrote: > > >No, you're incorrect. My retoucher friend knows exactly what she's > >talking about. She does fantastic work and is in great demand among pro > >shooters at about $200 an hour. > > I'm not disputing the ability of your friend to do good work > (spectacularly good work in the case of the example you showed) or that > she's worth $200.00 per hour. But her statements about the > differences/merits of making tonal changes before and after greyscale > conversion are factually incorrect, given the laws of physics and > trichromatic color systems. > > How would she treat my example of a scene consisting of shades of gray, > red and green that came out exactly the same after conversion? Only by > selecting and masking different areas and applying levels/curves to each > area separately. It's certainly a valid way of working, but it makes the > statement that those using channel mixer recipes (a one-click action) > have too much time on their hands a bit silly. > > >Sometimes she will go back and alter the color image to change the > >conversion, > > That's the only way certain changes can be made. > > >but she's more likely to tinker with it after the fact. > >She frequently uses curves and masks after the fact if more control > >is needed. > > Exactly. > > >But she points out that the PhotoShop grayscale conversion provides an > >accurate translation of a given color scene. > > Photoshop provides a *consistent* ratio of red-to-green-to-blue in > greyscale conversion. But what is an "accurate" conversion? An accurate > duplication of how Tri-X sees color? Or HP-5? Or any one of innumerable > other B&W films? And even then the accuracy of the greyscale conversion > is affected heavily by the color balance of the film or digital sensor > that did the original color capture. > > >It's quite close to what the values would have been if shot without > >filtration. > > On what film? That's the question. (And "what if you wanted to take a > shot *with* filtration?") > > >She did the conversion and some after the > >fact tuneup on my shot of the shoe shine man. > >http://www.photo.net/photodb/photo?photo_id=3451662 > > That's magnificent work. I would stress that I'm not criticizing the > quality of her work, the utility of her methods or the value of her > services. Only her understanding of the physics involved. She's clearly > developed an elaborate workflow that uses masks to work around what's > being missed in the greyscale conversion (not necessarily in this > particular example). > > The final *result*, in the end, is what's really important but it's not > right that she dismiss the approach of others simply because she doesn't > understand principles that are taught in freshman year of any good > photography program. > > > -- > Mark Roberts > Photography and writing > www.robertstech.com >
