I use a manual camera because my technique requires me to strictly control all parameters.
Various parameters play a role in photography: the time of the exposure, the width of the diaphragm and the film. The opening of the diaphragm has an influence on the quantity of light entering the camera. So does the time of the exposure, meaning that one is not independent from the other. As in many things, choices have to be made.
I fix my exposure time on 30 minutes and then adjust the diaphragm. I use very insensitive films, because I want long exposure times.
Itís easy to realize long exposure times during the night. A camera, a tripod, thatís all you need. From 15 minutes on the stars and the moon start leaving a trace. Working with long exposures during the day is more complicated. Insensitive films and a small diaphragm are not enough. You need a filter! I use the ND400 because it lets pass only 1 / 10 000 part of the light.
An important issue with this kind of photography is the non-linearity of the film. Beyond a certain exposure time, films donít react in a linear way anymore. There's no more proportionality between fast and slow exposures. Colours films are built of several layers, sensitive to different principal colours (as in our vision). Different layers have different degrees of non-linearity so that, from a certain exposure time on, the film cannot record true colours anymore. Thatís why the colours change. One can try to resolve the problem using filters, but I made the choice to accept this effect as part of my work.
This unpredictable element contrasts with the strict procedure I use to set the exposure time and the diaphragm.
Actual material: Mamiya 7 II - Lens, wide angle, Mamiya N 43 mm - Overview - Filter ND 400 (1/10 000) - Fujichrome Professional Velvia 100F - Trigger - Tripod Manfrotto
My ex-material: Nikon FM2 - Lens, wide angle, 17 mm - Filter ND 400 (1/10 000) - Filter ND 8 (1/8)
- Films Fuji chrome 100 et 50 (Velvia et Provia) - Tripod - Trigger - Black cloth
I used to use the Kodak chrome 25, but it doesnít exist anymore. The least sensitive film on the market now is the Velvia from Fujichrome.