Difference between revisions of "Retrofocus"
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'''Retrofocus''' refers to a type of lens design, pioneered (and originally trademarked) by [[Angénieux|Pierre Angénieux]] in the early 1950s,<ref>[https://worldwide.espacenet.com/patent/search?q=pn%3DUS2649022A US Patents 2649022], ''Wide-angle photographic objective lens assembly'', filed July 1950 and granted August 1953, and [https://worldwide.espacenet.com/patent/search?q=pn%3DUS2696758A 2696758], ''Wide-angle photographic objective'', filed March 1953 and granted December 1954 to Pierre Angénieux, both describing a retrofocus lens, at [http://worldwide.espacenet.com/ Espacenet], the patent search facility of the European Patent Office. The patents make reference to a French one of February 1950, not in the database at Espacenet.</ref> which permits a short lens optical [[Lens#Focal_Length|focal length]] while providing a greater back focus distance. This is typically required in an [[SLR]] camera, to allow space for the swinging reflex mirror; and also in some cine cameras using small image formats, to permit space for the shutter mechanism. | '''Retrofocus''' refers to a type of lens design, pioneered (and originally trademarked) by [[Angénieux|Pierre Angénieux]] in the early 1950s,<ref>[https://worldwide.espacenet.com/patent/search?q=pn%3DUS2649022A US Patents 2649022], ''Wide-angle photographic objective lens assembly'', filed July 1950 and granted August 1953, and [https://worldwide.espacenet.com/patent/search?q=pn%3DUS2696758A 2696758], ''Wide-angle photographic objective'', filed March 1953 and granted December 1954 to Pierre Angénieux, both describing a retrofocus lens, at [http://worldwide.espacenet.com/ Espacenet], the patent search facility of the European Patent Office. The patents make reference to a French one of February 1950, not in the database at Espacenet.</ref> which permits a short lens optical [[Lens#Focal_Length|focal length]] while providing a greater back focus distance. This is typically required in an [[SLR]] camera, to allow space for the swinging reflex mirror; and also in some cine cameras using small image formats, to permit space for the shutter mechanism. | ||
| − | Sometimes known as a "reverse [[ | + | Sometimes known as a "reverse [[telephoto]]" design, retrofocus designs typically have outermost lens groups with negative power, with convergent elements behind them. It can be difficult to design a retrofocus lens that is fully free from [[Lens#Distortion|barrel distortion]]. |
Since the rear element is further away from the film/sensor plane, retrofocus lens designs also suffer less from [[vignetting]] than conventional ones (i.e. there is more even illumination across the image). | Since the rear element is further away from the film/sensor plane, retrofocus lens designs also suffer less from [[vignetting]] than conventional ones (i.e. there is more even illumination across the image). | ||
Revision as of 23:46, 12 November 2020
Glossary Terms
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| M42 Angénieux Retrofocus lens image by Woradate Pattayawan (Image rights) |
Retrofocus refers to a type of lens design, pioneered (and originally trademarked) by Pierre Angénieux in the early 1950s,[1] which permits a short lens optical focal length while providing a greater back focus distance. This is typically required in an SLR camera, to allow space for the swinging reflex mirror; and also in some cine cameras using small image formats, to permit space for the shutter mechanism.
Sometimes known as a "reverse telephoto" design, retrofocus designs typically have outermost lens groups with negative power, with convergent elements behind them. It can be difficult to design a retrofocus lens that is fully free from barrel distortion.
Since the rear element is further away from the film/sensor plane, retrofocus lens designs also suffer less from vignetting than conventional ones (i.e. there is more even illumination across the image).
Notes
- ↑ US Patents 2649022, Wide-angle photographic objective lens assembly, filed July 1950 and granted August 1953, and 2696758, Wide-angle photographic objective, filed March 1953 and granted December 1954 to Pierre Angénieux, both describing a retrofocus lens, at Espacenet, the patent search facility of the European Patent Office. The patents make reference to a French one of February 1950, not in the database at Espacenet.
Links
- Angénieux Retrofocus 28/3.5 lenses in black and chrome finish, sold at the fourth Westlicht Photographica Auction, 22 November 2003.
