A plastic or glass plate on which the image entering a reflex camera is reflected on by a mirror.
While most modern consumer autofocus (D)SLRs are only sold with a plain matte screen and no official alternatives exist, aftermarket replacement are popular among users of manual focus lenses who do not trust or can't use the focus confirmation signal from the AF system.
They may be of various types:
- With or without a composition and/or perspective assisting grid;
- With or without frame lines for cropping to a predetermined aspect ratio;
With or without etched ring(s) highlighting centerweighted, partial or spot metering areas;
Matte or fresnel, with the latter not rendering out-of-focus areas as such;
- With or without a splitting prism which visually breaks out of focus elements: variants exist such as horizontal 180° split, single or double 45° diagonal split, …
- With or without a microprism array field or ring, which render out-of-focus areas as having a distinctive crystalized appearance.