Look at the deep shadow areas of your negatives. These areas should look nearly as clear as the unexposed parts of the film. Find or make a negative with the thinnest part of the image at the edge of the frame, the edge should be just visible. This is approximately your minimum exposure for full shadow detail. A contrasty scene will need a little more exposure, a soft scene a little less. Tri-X's latitude can absorb about two stops over exposure with little trouble, so you can shoot it at 200 or even 100 even if you might get decent shadow details at 320-400. The image will be sharper and less grainy at the minimum exposure though.(posted 9675 days ago)If you learn to read your negatives visually and adjust development and exposure in small steps you can fine tune your technique.