Single lens reflex (SLR).
A type of camera in which the photographer looks through the actual taking lens when he or she peers through the viewfinder.
Light entering an SLR camera lens hits a mirror installed in the body at a 45° angle, which deflects the light up into the viewfinder pentaprism. When the photograph is actually taken the mirror flips up out of the way, the shutter opens and light strikes the surface of the film behind it. (the one exception being fixed pellicle mirror SLRs)
SLRs have a couple of very significant advantages. First, they do not suffer from parallax error, which makes them useful for closeup or macro photography. Second, what you see is mostly what you get - you can see the effects of filters, for example, before you take the photo. The image in an SLR viewfinder is also not reversed or upside-down, as is the case with TLRs and view cameras.
There are also a number of disadvantages to SLRs. First, the pentaprism is bulky - its the large hump on the top of an SLR. Second, the noise of the mirror slap means that SLRs are always much louder to operate than, say, rangefinders. Third, there is a brief mirror blackout period on most SLRs during which nothing can be seen in the viewfinder (fixed pellicle mirror SLRs being the one exception again). And finally, the mirror forms a physical barrier for the design of very wide-angle lenses, requiring inverted telephoto construction.
cf. Contax, ground glass, instant return, inverted telephoto lens, mirror blackout, mirror slap, parallax, pellicle mirror, pentaprism, rangefinder, reflex mirror, taking lens, twin-lens reflex (TLR), viewfinder.
Entry last updated 2002-04-16. Term 1126 of 1487.
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