Pere: Please do NOT rely on the link you cited in post 10. It contains misleading and erroneous information. Most important, the critical depth to film surface is actually the distance from the film holder to the septum. The distance to the emulsion can be as much as 0.012 inches or 0.3mm less. This error can cause a noticeable loss in sharpness when using fast lenses. The exposure height figures are obviously wrong. The figures do not include tolerances, which should be important to anyone relying on them to produce film holders.