Archived posting to the Leica Users Group, 1999/10/17
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]>As you know, by push processing the shadows hardly improve, only the >middle values and the curve will be a bit steeper. So this action >(steeper gradient) and character (short toe) might reduce the -3 and >-4 frames into deep black (no details visible). >Generally when you use B&W negative film at its correct ISO speed, >you will hardly notice any texture or grey density in the -4 frame. Should I try rating the film a little slower to get the >fifth exposure discernable from base fog? > >Yes the method is correctly applied. To lower the exposure to get the shadows >back and at the same time deciding to push the film will cancel out. >If you need shadows you cannot push (or you should overexpose >consciously when taking the picture, being aware of what you are >doing) and if you need pushing you lose some deep shadows. > >Erwin I seem to recall that Erwin said, when he wrote first about film speed test, that if you make a film speed test at nominal film speed, then you will get no useable details on the minus-4 negative (Zone I as per Ansel Adams) in spite of the definition of film speed being the speed which would give some useable shadow detail when underexposed four steps. Erwin went on to say that the lack of detail in the minus-four negative should not worry you, unless you wanted some print detail even in the darkest shadow. If not, you should just continue to use the nominal speed. I think this is such a sound piece of advice that it warrants being repeated here now. If I recall correctly, for the film speed test Erwin suggested one correct exposure and four overexposures and four underexposures, with one f-stop (or the time equivalent difference) between each exposure. I think it is useful to make more exposures, five or even six over/underexposures, and to develop several film strips (i.e. half films) at the manufacturer's recommended time and then also at recommended time plus 10 and 20 and 30 percent. This shows cleary both where the limits of pushing are in the shadow details, and the effect of highlight blocking. With a few more exposures you are really shure that nothing happens in the shadows however long you develop but that it has effects on the highlights. Unfortunately you need at densiometer (or something equivalent, like the Analyser) if you want to make a film speed test without too much work. - -- christer almqvist eichenstrasse 57, d-20255 hamburg, fon +49-40-407111 fax +49-40-4908440 14 rue de la hauteur, f-50590 regnéville-sur-mer, fon+fax +33-233 45 35 58