[usually as modifier] An area of the focusing screen of some reflex cameras which is covered with a grid of tiny prisms and splits up the image when the subject is not in focus.
- ‘Plain screens are available without the central split-image and microprisms, and these are suitable for × 1 to about × 4.’
- ‘Be careful to position your eye in the center of the finder to be able to see all the microprisms; some will black out if your eye is uncentered.’
- ‘This can be distinguished by the diamond-shaped lattice separating the sheeting layers, and a ‘coarse’ grain to the microprisms.’
- ‘An array of lenticular microlenses may be positioned to accept the output of the microprisms so that the light exiting from the microlenses is a substantially collimated light source.’
- ‘Although the array of microprisms used at Keck would probably be difficult to expand by large factors, we have shown in a series of laboratory measurements that commercially available microlenslet arrays are now of sufficient quality to constitute a viable substitute for microprisms.’