And, of course, with B&W film, there's a lot more control on the processing end, so one can "over expose" the film, or expose for the shadows, and develop for the highlights, so that there are no blown highlights. So, for a Q&D example, you can rate TX @ 200, cut back the standard processing time by 25% or so, and get a negative that will print quite well.
Shel > [Original Message] > From: John Francis > Paul Stenquist wrote: > > Your example is extreme, but most films seem to be slightly overrated > > in regard to ISO. > > Hardly. The ISO testing procedure is well-defined, and rigorously > followed. If a film says ISO 400 on the box, you can be darn sure > that it will score 400 on the ISO measurement scale. > > But that doesn't mean blindly loading a DX-coded cassette into > your camera, pointing the camera at a random scene, and letting > that determine the exposure will produce the results you want > (even assuming the average brightness of your subject is anywhere > close to 12% grey). Furthermore, shifting the exposure up the > scale (which is what you do if you rate the film at slower than > the box speed) will decrease noise in the shadows at the cost of > possibly blowing out the highlights, while shifting downwards > towards under-exposure will generally increase colour saturation. > It's all a matter of choosing what effect you want, and then > deciding which film to use, and how to rate it, in order to > get close to that result. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
