Difference between revisions of "Pentaprism"
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| − | A '''Pentaprism''' is a five-sided optical glass element that reflects light through 90°. | + | A '''Pentaprism''' is a five-sided optical glass element that reflects light through 90°. The variant used in most SLR's (and pentaprism finders for system TLR's) is the ''roof pentaprism'', which has two sloping sides on one of the reflecting surfaces, usually the top, to allow light from the mirror 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, making framing difficult, and following a moving subject confusing. The roof pentaprism is the reason for most SLR cameras having a triangular top to their viewfinders. |
{{Flickr_image | {{Flickr_image | ||
|image_source= http://www.flickr.com/photos/24225011@N04/2345422972/in/pool-camerawiki/ | |image_source= http://www.flickr.com/photos/24225011@N04/2345422972/in/pool-camerawiki/ | ||
Latest revision as of 23:19, 23 April 2020
A Pentaprism is a five-sided optical glass element that reflects light through 90°. The variant used in most SLR's (and pentaprism finders for system TLR's) is the roof pentaprism, which has two sloping sides on one of the reflecting surfaces, usually the top, to allow light from the mirror 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, making framing difficult, and following a moving subject 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, then through the eyepiece lens (Ocular) to the eye. image by AWCam (Image rights) |
Links
- Viewfinder Types on Ted's Photographics by Ted Ellis
- Wikipedia Pentaprism article
