Also fixed reflex mirror. An SLR reflex mirror which is partially transparent and does not move.
One of the advantages of traditional moving-mirror SLR cameras is that the photographer can look through the viewfinder and see what the actual taking lens is seeing. The primary disadvantage is mirror blackout - when the mirror has flipped up to expose the film then nothing can be seen through the viewfinder. Mirror blackout, though brief at high shutter speeds, can nonetheless be a problem for sports and other action photography.
Cameras with pellicle mirrors have fixed half-silvered mirrors that both direct light to the viewfinder and to the film surface. They therefore eliminate mirror blackout whilst preserving the advantages of an SLR. They are also much quieter, as there are no mirror slap sounds or blur-inducing vibrations caused by mirror motion. Pellicle mirror cameras can also shoot almost instantly - unlike most SLRs theres no lag time resulting from having to move the mirror out of the way. This rapid-fire capability also permits faster film transport mechanisms in some cases.
Pellicle mirror cameras have two drawbacks. First, the mirror must be kept scrupulously clean because light passes through it to the film surface. Second, because some of the light is being diverted up to the viewfinder theres less light available to the film. Pellicle mirrors typically cost 2/3 stop of light and the viewfinder is also a bit dimmer.
A pellicle is a membrane or a thin film and refers in this case to the very thin reflective coating on the mirror.
cf. lag time, mirror, mirror blackout, mirror lockup, mirror slap, reflex mirror, single lens reflex (SLR).
Entry last updated 2002-04-16. Term 891 of 1487.
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