Abstract: An exposure mask for photographic material has a measuring wheel and two adjustable mask blades. Movement of the photographic material causes rotation of the wheel, which causes a switching member to rotate. Whenever the switching member reaches a given position it operates a switch and stops the transport of the material. Adjustment of one mask blade adjusts the rate of rotation of the switching member relative to that of the measuring wheel by adjusting the axial position of a frustoconical roller that rests on the measuring wheel and drives the switching member.

Abstract: An exposure mask 9 for photographic material 4 includes a measuring wheel 23 and two adjustable mask blades 19 and 20. Movement of the photographic material 4 causes rotation of the wheel 23, which causes a switching member 34 to approach a switch 42. When the switching member 34 reaches the switch 42 it stops the transport of the material 4. Adjustment of one mask blade 20 adjusts the initial distance between the switching member 34 and the switch 42.

Abstract: A light-diffuser for a photographic copier such as an enlarger incorporates a closely contacting parallel row of elongated glass rods held between a pair of tracks. The rods are preferably of heat-resistant glass of round cross section. An additional row of such rods may be disposed parallel to the first row and staggered therefrom to improve the diffusion of a beam of light passing through them.