gvaliquette Posted May 18, 2013 Share #21  Posted May 18, 2013 Advertisement (gone after registration) Exactly  "Retrofocus-like" (as opposed to "retrofocus") means, "increased backfocus distance, yet not quite retrofocus." As I've already explained.  01af,  Let's not split hairs here. Retrofocus lens design was developed by Angenieux for, first, a 35 mm lens, and then, a 28 mm lens for early reflex cameras (Alpa, Exacta) and was copyrighted by Angenieux. The design does not specify a minimal distance between the rear element and the focal plane. "Retrofocus" and "retrofocus-like" lens designs are the same lens designs.  Guy Link to post Share on other sites More sharing options...
Advertisement Posted May 18, 2013 Posted May 18, 2013 Hi gvaliquette, Take a look here Rectilinear ultra-wide. I'm sure you'll find what you were looking for!
01af Posted May 18, 2013 Share #22 Â Posted May 18, 2013 Let's not split hairs here. Who's splitting hairs? "Retrofocus" is a technical term with a clearly defined meaning. It means, "backfocus distance greater than focal length" (at infinity focus). As simple as that. Link to post Share on other sites More sharing options...
Peter Branch Posted May 20, 2013 Share #23 Â Posted May 20, 2013 Who's splitting hairs? "Retrofocus" is a technical term with a clearly defined meaning. It means, "backfocus distance greater than focal length" (at infinity focus). As simple as that. Â This begs the question of what is meant by "Backfocus". Authoritative sources are not in agreement on this point. Similarly with the term "Telephoto". Â I suggest both describe a type of lens design which affords a feature that is beneficial in certain circumstances. It must be remembered that early lenses for use on bellows cameras were sometimes designed with interchangable components which gave a range of focal lengths - some telephoto, a negative lens behind a positive one, sometimes variable separation and some retrofocus with a negative lens in front of a positive one. Results were mixed. Link to post Share on other sites More sharing options...
01af Posted May 20, 2013 Share #24 Â Posted May 20, 2013 Authoritative sources are not in agreement on this point. Don't worry, they are. Laymen who consider themselves 'authoritative' possibly aren't. Link to post Share on other sites More sharing options...
henning Posted May 21, 2013 Share #25  Posted May 21, 2013 Exactly  "Retrofocus-like" (as opposed to "retrofocus") means, "increased backfocus distance, yet not quite retrofocus." As I've already explained.  Retrofocus is any construction where the exit pupil sits further from the film/sensor plane than the focal length. How much it is retrofocus is another matter; but retrofocus is what these lenses are. The 'moustache' type of distortion that these lenses exhibit is typical for this type of construction.  This is my last post on this topic as there is clearly an unwillingness to learn.  Henning Link to post Share on other sites More sharing options...
01af Posted May 21, 2013 Share #26 Â Posted May 21, 2013 Retrofocus is any construction where the exit pupil sits further from the film/sensor plane than the focal length. The position of the exit pupil has nothing to do with it. Â Â This is my last post on this topic as there is clearly an unwillingness to learn. Sorry to hear that you're unwilling to learn. Link to post Share on other sites More sharing options...
jaapv Posted May 21, 2013 Share #27 Â Posted May 21, 2013 Advertisement (gone after registration) Maybe it is more clear to refer to "Reverse Telephoto" lenses. Although it is not quite the same the concepts are fairly interchangeable nowadays. Link to post Share on other sites More sharing options...
01af Posted May 21, 2013 Share #28 Â Posted May 21, 2013 Maybe it is more clear to refer to "Reverse Telephoto" lenses. I don't see how a wrong term or explanation would be helpful to make anything clearer. It's like explaining the smaller angle-of-view for lenses used on smaller-format cameras as, 'the focal length becomes longer.' This only seems to be the easiest way to explain it but, when taken for real, inevitably will only cause confusion later. Â Â Although it is not quite the same ... Exactly. There is some truth in explaining retrofocus as 'reverse telephoto' ... but that's not really what it is. Apart from the fact that most people don't really know that a telephoto lens is in the first place. It's the design principle that gets reversed, not the result. When actually physically reversing a retrofocus lens then you won't get a telephoto lens. And when reversing a telephoto lens, you don't get a retrofocus lens. Link to post Share on other sites More sharing options...
jaapv Posted May 21, 2013 Share #29 Â Posted May 21, 2013 Well, if using technically correct explanations only leads to disagreements and not to understanding some simplification of terms seems to be in order. Obviously I referred to the design principle, not to a physical lens. Keeping everybody on his toes is not helped by stepping on them... Link to post Share on other sites More sharing options...
jankap Posted June 3, 2013 Share #30 Â Posted June 3, 2013 Does somebody have gone the way fisheye lens + software fisheye-hemi? So converting the fisheye projection to a rectilinear one. There is the lens Elmarit R 15/2.8! Jan Link to post Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.