Difference between revisions of "Pentaprism"
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| − | A '''Pentaprism''' is a five-sided optical glass element that reflects light through 90°. A variant, the ''roof pentaprism'', has two sloping sides on one of the reflecting surfaces, usually the top, to allow light from the mirror of an [[SLR]] to be reflected into an eye-level [[Reflex finder|(reflex) viewfinder]] with the picture appearing the correct way around to the photographer. This avoids the problem suffered by other reflex viewfinder systems, which can have the image laterally (left-right) reversed | + | A '''Pentaprism''' is a five-sided optical glass element that reflects light through 90°. A variant, the ''roof pentaprism'', has two sloping sides on one of the reflecting surfaces, usually the top, to allow light from the mirror of an [[SLR]] to be reflected into an eye-level [[Reflex finder|(reflex) viewfinder]] with the picture appearing the correct way around to the photographer. This avoids the problem suffered by other reflex viewfinder systems, which can have the image laterally (left-right) reversed - or even upside-down if you rotated the camera - making following a moving subject difficult or confusing. The roof pentaprism is the reason for most SLR cameras having a triangular top to their viewfinders. |
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|image_source= http://www.flickr.com/photos/24225011@N04/2345422972/ | |image_source= http://www.flickr.com/photos/24225011@N04/2345422972/ | ||
Revision as of 12:01, 19 March 2008
This is a work in progress.
A Pentaprism is a five-sided optical glass element that reflects light through 90°. A variant, the roof pentaprism, has two sloping sides on one of the reflecting surfaces, usually the top, to allow light from the mirror of an SLR to be reflected into an eye-level (reflex) viewfinder with the picture appearing the correct way around to the photographer. This avoids the problem suffered by other reflex viewfinder systems, which can have the image laterally (left-right) reversed - or even upside-down if you rotated the camera - making following a moving subject difficult or confusing. The roof pentaprism is the reason for most SLR cameras having a triangular top to their viewfinders.
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| Light from the subject goes through the lens, is reflected from the mirror, then is flipped through the pentaprism, through the eyepiece lens to the eye. |
Links
- Viewfinder Types on Ted's Photographics by Ted Ellis
- Wikipedia Pentaprism article
