CheshireCat Posted July 2, 2013 Share #121 Posted July 2, 2013 Advertisement (gone after registration) Google "retro focus lenses", and you'll soon discover why rangefinder/MF/LF wide angle lenses are superior to those made for dSLRs. I am not interested in "actual data and photos" produced by you unless they've some artistic merit. For objective analysis of lens design, I'll stick with scientists. Please Google "retro focus lenses" and the difficulties/complexities involved in designing wide angle lenses for SLRs. I read this forum on my mobile and can not provide you with specific links. If you are genuinely interested, you'll take the time to do some research. Please do yourself a favor, and search for "retrofocus" in this doc: http://us.leica-camera.com/assets/file/download.php?filename=file_6030.pdf Link to post Share on other sites More sharing options...
Advertisement Posted July 2, 2013 Posted July 2, 2013 Hi CheshireCat, Take a look here diglloyd: "Leica M Typ240: Unreliable". I'm sure you'll find what you were looking for!
jaapv Posted July 2, 2013 Share #122 Posted July 2, 2013 Umm.. That document makes it clear that the Super-Elmar 21 is not a retrofocus design, but a "retrofocus-like"design. Leica knows the difference, obviously. Having said that, there is a convergence in lens design between SLR lenses and rangefinder lenses. Originally SLR lenses had to be designed to clear the mirror, and retrofocus was an answer to that problem. Over the years, as designers mastered the difficulties of the design, they found that non-symmetrical lenses gave more freedom for correcting aberrations and started using design elements from the SLR world for rangefinder lenses. With the edge problems of sensors this this turns out to be a blessing in disguise. Nowadays the division between SLR lenses and rangefinder lenses has largely disappeared in this respect, and it is rather moot to discuss whether a lens is "retrofocus", "non-retrofocus" or "retrofocus-like." Link to post Share on other sites More sharing options...
01af Posted July 2, 2013 Share #123 Posted July 2, 2013 Please do yourself a favor, and search for "retrofocus" in this doc: [...] Please do yourself a favour and note that "retrofocus-like" does not mean "retrofocus". A traditional, near-symmetric 21 mm super-wide-angle lens (for 35-mm format) typically has a backfocus distance of 10 - 12 mm. The Super-Elmar-M 21 mm Asph's back-focus distance is only slightly longer than that; it's 15.4 mm. A retro-focus 21 mm lens has a backfocus distance of more than 21 mm—those made for 35-mm-format SLR cameras have about 40 mm. So the Super-Elmar-M 21 mm Asph is still far from being a retrofocus lens. As a matter of fact, no lens in the current Leica M line-up is retrofocus, with the exception of the Tri-Elmar-M 16-18-21 mm Asph. Link to post Share on other sites More sharing options...
jaapv Posted July 2, 2013 Share #124 Posted July 2, 2013 The use of retro-focus-like is slightly misleading in this context. Non-symmetric would be a better description. Link to post Share on other sites More sharing options...
sydkugelmass Posted July 2, 2013 Share #125 Posted July 2, 2013 Are 'retrofocus-like' designs able to map straight lines to straight lines with near-to-nil distortion? Can the ZM Biogon 21mm/f4,5 be called a 'symmetric-like' design? What about straight lines rendering with the Hologons? Link to post Share on other sites More sharing options...
jaapv Posted July 2, 2013 Share #126 Posted July 2, 2013 In general a non-symmetric design will give more freedom for corrections, but will be more challenging. Link to post Share on other sites More sharing options...
01af Posted July 2, 2013 Share #127 Posted July 2, 2013 Advertisement (gone after registration) The use of retrofocus-like is slightly misleading in this context. I agree, albeit I'd take away the word "slightly" ... in fact, it's highly misleading. Non-symmetric would be a better description. I don't think so, because the design actually is still fairly close to symmetric. Link to post Share on other sites More sharing options...
pgk Posted July 2, 2013 Share #128 Posted July 2, 2013 A traditional, near-symmetric 21 mm super-wide-angle lens (for 35-mm format) typically has a backfocus distance of 10 - 12 mm. The Super-Elmar-M 21 mm Asph's back-focus distance is only slightly longer than that; it's 15.4 mm. A retro-focus 21 mm lens has a backfocus distance of more than 21 mm—those made for 35-mm-format SLR cameras have about 40 mm. So the Super-Elmar-M 21 mm Asph is still far from being a retrofocus lens. As a matter of fact, no lens in the current Leica M line-up is retrofocus, with the exception of the Tri-Elmar-M 16-18-21 mm Asph. Interesting. For information can I add that the 'back focal length' (I'm quoting) for the 'traditional' 21mm f/3.4 Super-Angulon-M is actually stated as being 8.3mm by Schneider its manufacturer. Unfortunately I have never found measured distortion figures for this lens. The 21mm Elmarit-M and 21mm Super Elmar-M show similar distortion levels to each other (peaking at under 2%) whilst the Tri-Elmar-M has greater distortion at wider focal lengths but again similar levels at 21mm. Having tried/used all these lenses my subjective view is that the Super Angulon distorts least, but has most problems with colour shift on digital sensors. Link to post Share on other sites More sharing options...
jaapv Posted July 2, 2013 Share #129 Posted July 2, 2013 I don't think so, because the design actually is still fairly close to symmetric. Like "fairly close to being pregnant"? Link to post Share on other sites More sharing options...
colonel Posted July 2, 2013 Share #130 Posted July 2, 2013 Like "fairly close to being pregnant"? done that, been their Link to post Share on other sites More sharing options...
CheshireCat Posted July 2, 2013 Share #131 Posted July 2, 2013 Please do yourself a favour and note that "retrofocus-like" does not mean "retrofocus". A traditional, near-symmetric 21 mm super-wide-angle lens (for 35-mm format) typically has a backfocus distance of 10 - 12 mm. The Super-Elmar-M 21 mm Asph's back-focus distance is only slightly longer than that; it's 15.4 mm. A retro-focus 21 mm lens has a backfocus distance of more than 21 mm—those made for 35-mm-format SLR cameras have about 40 mm. So the Super-Elmar-M 21 mm Asph is still far from being a retrofocus lens. As a matter of fact, no lens in the current Leica M line-up is retrofocus, with the exception of the Tri-Elmar-M 16-18-21 mm Asph. You fail to understand that a retrofocus lens is simply a lens that uses negative groups at the back to increase the BFD for some purpose. In SLR the purpose is usually fitting the mirror, and for Leica M the purpose is decreasing the inclination of rays to avoid horrible color casts and fitting more elements for a better correction. Your "BFD being more than the FL" is the only misleading concept in this thread. Leica literature clearly defines the SEM as a retrofocus-like design, and retrofocus it is because of the negative groups, increased BFD, and clearly asymmetrical design. This and the fact that the SEM is an amazing lens, should be enough to prove my point: a retrofocus lens (even by your definition) can be much better than a symmetrical design. Just requires a great design, more elements, and great glass. Link to post Share on other sites More sharing options...
01af Posted July 2, 2013 Share #132 Posted July 2, 2013 A traditional, near-symmetric 21 mm super-wide-angle lens (for 35-mm format) typically has a backfocus distance of 10 - 12 mm.Interesting. For information can I add that the 'back focal length' (I'm quoting) ... Who exactly are you quoting? ... for the 'traditional' Super-Angulon 21 mm 1:3.4 is actually stated as being 8.3 mm by Schneider ... Okay—so make that "typically has a backfocus distance of 8 - 12 mm." My Minolta W.Rokkor-PI 21 mm 1:4.5 from the late '60s, for instance, is 11.5 mm. ... the design [of the Super-Elmar-M 21 mm Asph] actually is still fairly close to symmetric.Like "fairly close to being pregnant"? Very funny. You are aware that even the Schneider Super-Angulon lenses aren't really symmetric, aren't you? You fail to understand that a retrofocus lens is simply a lens that uses negative groups at the back to increase the backfocus distance for some purpose. In fact, it's you who fails to understand—in more than one respect—what "retrofocus" is and means. Let's just say that the quality of a wide-angle lens depends on many factors but not on the design being truely retrofocus, retrofocus-like, or not retrofocus at all. Link to post Share on other sites More sharing options...
sunil Posted July 2, 2013 Share #133 Posted July 2, 2013 "I just got a new MacBook Air that has a bad speaker and the display flickers. I didn't post a review about these problems and state my personal opinions about its operation, like the electronic screen doesn't stay on when you turn off the power or that the buttons are hard to get used to. No, I took it back to the store and got a new one." Wow!! I wish we could do that with the M(240). Link to post Share on other sites More sharing options...
Rick Posted July 3, 2013 Share #134 Posted July 3, 2013 "I just got a new MacBook Air that has a bad speaker and the display flickers. I didn't post a review about these problems and state my personal opinions about its operation, like the electronic screen doesn't stay on when you turn off the power or that the buttons are hard to get used to. No, I took it back to the store and got a new one." Wow!! I wish we could do that with the M(240). You can. Walk in and up to the counter, muster all of your nerve, take out your parents credit card and politely ask for your money back or ask for an exchange. Unless, you are going after the technicality that it won't be in stock and you have to wait. Do you need to take your camera back? Or, are you one of the complaining non-owners that seem to have populated the forum? Link to post Share on other sites More sharing options...
k-hawinkler Posted July 3, 2013 Share #135 Posted July 3, 2013 You can. Walk in and up to the counter, muster all of your nerve, take out your parents credit card and politely ask for your money back or ask for an exchange. Unless, you are going after the technicality that it won't be in stock and you have to wait. Do you need to take your camera back? Or, are you one of the complaining non-owners that seem to have populated the forum? Rick, What do you think a forum members role is? I think you are crossing the line again. Link to post Share on other sites More sharing options...
CheshireCat Posted July 3, 2013 Share #136 Posted July 3, 2013 In fact, it's you who fails to understand—in more than one respect—what "retrofocus" is and means. Feel free to stick to your rules of thumb. Link to post Share on other sites More sharing options...
Rick Posted July 3, 2013 Share #137 Posted July 3, 2013 Rick, What do you think a forum members role is? I think you are crossing the line again. I don't see any difference between what I stated and the posts by a minority of members pointing out the existence of many non-complaining Leica fanboy owners, stating that we are doing some disservice by not agreeing that there is something really flawed about the new M. The only difference I can see is that when the shoe is on the other foot, you claim some line is being crossed. I'm tired of the double standard. I like the camera. Get over it. Link to post Share on other sites More sharing options...
Guest WPalank Posted July 3, 2013 Share #138 Posted July 3, 2013 Had a lock up yesterday with my M9P. But all the pictures were "purty". Link to post Share on other sites More sharing options...
CaptZoom Posted July 3, 2013 Share #139 Posted July 3, 2013 Experienced my first lockup yesterday (M9) in over three years, and now I feel like I'm finally a bone fide member of the digital Leica fraternity:) Link to post Share on other sites More sharing options...
Rick Posted July 3, 2013 Share #140 Posted July 3, 2013 Experienced my first lockup yesterday (M9) in over three years... What a piece of *unreliable junk. *Unreliable; As defined by Marc the professional photographer: "Zero lock-ups, zero failures, zero missed shots due to equipment hiccups, need to reboot, or remove the battery and start up agin. Zero. Subjectively, for my needs, I'd call that reliable ... anything less ... isn't." - Marc And, as Marc tells us again and again, we must respect the professional photographers. They are professionals... not just a "Travel Log" Leica Fanboy. Link to post Share on other sites More sharing options...
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