michaelwj Posted May 10, 2016 Share #61 Â Posted May 10, 2016 Advertisement (gone after registration) I'm learning new things every day on this great forum. We all do. If I could pay back 1% of what I've learnt here it would be amazing. Link to post Share on other sites More sharing options...
T*Sonnar Posted May 10, 2016 Share #62 Â Posted May 10, 2016 I'm learning new things every day on this great forum. Â Even after 13,641 posts ? I have a lot to look forward to ;-) Link to post Share on other sites More sharing options...
T*Sonnar Posted May 10, 2016 Share #63  Posted May 10, 2016 ? How does less distortion lead to more distorted faces? Less distortion would surely have less distorted faces. A lens without distortion doesn't need correcting. Michael  Because a perfectly corrected lens has the appearance of stretching in the corners. I thought that was clear by now. The Super-Elmar is one such example. It has next to no lens-distortion, and so doesn't need 'correction'. But that of course is not ideal for every purpose as it leads to distorted faces etc. Link to post Share on other sites More sharing options...
michaelwj Posted May 10, 2016 Share #64 Â Posted May 10, 2016 Because a perfectly corrected lens has the appearance of stretching in the corners. I thought that was clear by now. The Super-Elmar is one such example. It has next to no lens-distortion, and so doesn't need 'correction'. But that of course is not ideal for every purpose as it leads to distorted faces etc. The Super-Elmar is very well corrected for geometric distortion, and as a result has horrible stretched out corners! Stretched out corners is a type of distortion. The result of making an asymmetrical lens free from geometric distortion. The world isn't stretched out in the corners! Ideally a stitch from a 50mm lens will look much more natural, it's just hard on a moving subject. Â It is very difficult to design a wide angle lens (especially a small one) that has even illumination, high and even resolution, and is free from all distortion. Â The Super-Elmar and Super Angulon both do very well in some areas but not others. Neither is perfect, but both are excellent. This is the beauty of using a Leica - both options (and everything in between) are available and work with full functionality over a 60 year history. Link to post Share on other sites More sharing options...
T*Sonnar Posted May 10, 2016 Share #65 Â Posted May 10, 2016 Indeed. That's exactly it. Â Others will say they love the Super-Elmar because it has such perfectly straight lines. It's not a con for everyone. For some it may as well be perfect. Â After Edit: Â A stitch will not be any different. If you use a planar projection that is geometrically correct the result will be exactly the same and appear stretched. Â Ceci n'est pas une pipe. It's just a matter of projection that we're not used to seeing. Got nothing to do with how things are, but how we (want to) see them. Link to post Share on other sites More sharing options...
michaelwj Posted May 10, 2016 Share #66 Â Posted May 10, 2016 Indeed. That's exactly it. Â Others will say they love the Super-Elmar because it has such perfectly straight lines. It's not a con for everyone. For some it may as well be perfect. Â After Edit: Â A stitch will not be any different. If you use a planar projection that is geometrically correct the result will be exactly the same and appear stretched. Â Ceci n'est pas une pipe. It's just a matter of projection that we're not used to seeing. Got nothing to do with how things are, but how we (want to) see them. Re: stitching, it will have a lot of other complications depending on how it is captured and stitched, but it is possible to not have stretched corners. Â And yes, it is exactly how you want to show what you see! Link to post Share on other sites More sharing options...
T*Sonnar Posted May 10, 2016 Share #67 Â Posted May 10, 2016 Advertisement (gone after registration) Anything is 'possible'. You can also un-correct the Super-Elmar to look more like the Super Angulon. Like i said, a matter of projection. The stitching is irrelevant in this respect, it does not make a difference. Link to post Share on other sites More sharing options...
the warrior Posted May 10, 2016 Share #68 Â Posted May 10, 2016 I have many problems with my poor English, I have to use Google translator and that's not right, it malfunctioned, again ask forgiveness for my mistakes.I can hardly understand many things that you who are wiser than I say, but I am very interested as soon hope to sell my Elmarit21,, f2.8 ASPH and buy a SA f4 or f3,4 SA, I have doubts still.I'll make a comparison with photographs, the three lenses on a tripod and the same lighting.Elmarirt ASPH, SA f4 and SA f3,4, but I limit myself to offering photos and write little to avoid my mistakes.I'm reading your interesting comments but I do not understand everything very well.Thank you for your knowledge of optics. Link to post Share on other sites More sharing options...
the warrior Posted May 10, 2016 Share #69 Â Posted May 10, 2016 You must have something in mind:My pictures with the SA f3,4 are made to 40 centimeters, the minimum focus of this lens, I'm not sure this will affect the outcome of the photos.40 centimeters short distance approach is the biggest reason for my change elmarit f2.8 ASPH by the SA.Another argument that I have read is that the SA is capable of a much higher DOF because of its design, is it true ?. Â Link to post Share on other sites More sharing options...
michaelwj Posted May 10, 2016 Share #70 Â Posted May 10, 2016 You must have something in mind: Â My pictures with the SA f3,4 are made to 40 centimeters, the minimum focus of this lens, I'm not sure this will affect the outcome of the photos. Â 40 centimeters short distance approach is the biggest reason for my change elmarit f2.8 ASPH by the SA. Â Another argument that I have read is that the SA is capable of a much higher DOF because of its design, is it true ?. DOF is a function of the aperture and focal length; so the physical size of the hole, and the "pixel size". 40cm is very handy in a wide angle. I think the early Elmarit can also focus to 40cm, we may have spoken about this before? Michael Link to post Share on other sites More sharing options...
michaelwj Posted May 10, 2016 Share #71  Posted May 10, 2016 Anything is 'possible'. You can also un-correct the Super-Elmar to look more like the Super Angulon. Like i said, a matter of projection. The stitching is irrelevant in this respect, it does not make a difference. Not everything is possible, you will lose something by trying to one lens look like the other, resolution, width, shape - it is not just a simple transform.  I don't follow your stitching comment? A 50mm shot does not stretch the corners, two of them do not stretch their respective corners, so it is only how they are taken and stitched that stretched corners can arise. So it is all about stitching. But we digress.  Michael  ps. It's nice to have near real time discussions. Link to post Share on other sites More sharing options...
the warrior Posted May 10, 2016 Share #72 Â Posted May 10, 2016 SA f3,4 in the bottom right corner is not as bulky as the 21mm Elmarit ASPH. Â Beer drinker looking boy in the photo above. Â Link to post Share on other sites More sharing options...
the warrior Posted May 10, 2016 Share #73 Â Posted May 10, 2016 Yes Michaelwj, I know well the rules for more DOF but apparently the symmetrical design is able to do more DOF in retrofocus design equal to circumstances, it is what I think I have read and maybe it's true.Even taking pictures just 40 centimeters from the people here seem more DOF than with elmarit to 70 centimeters, I think. Â The photo of the boy and his beer is f3,4, photo man with his ear device is made to f5.6 Link to post Share on other sites More sharing options...
the warrior Posted May 10, 2016 Share #74 Â Posted May 10, 2016 SA f3,4 in f 3.4 to 40 centimeters. Â Link to post Share on other sites More sharing options...
michaelwj Posted May 10, 2016 Share #75 Â Posted May 10, 2016 Yes Michaelwj, I know well the rules for more DOF but apparently the symmetrical design is able to do more DOF in retrofocus design equal to circumstances, it is what I think I have read and maybe it's true. Â Even taking pictures just 40 centimeters from the people here seem more DOF than with elmarit to 70 centimeters, I think. Â The photo of the boy and his beer is f3,4, photo man with his ear device is made to f5.6 I assumed you did! I found the question a bit puzzling! I haven't heard anything about the lens design influencing DOF, but I know that Leica changed the DOF scale during the SAs life. I believe they used Schneiders scale on the early models, before changing to their own. Â Michael Link to post Share on other sites More sharing options...
michaelwj Posted May 10, 2016 Share #76 Â Posted May 10, 2016 SA f3,4 in the bottom right corner is not as bulky as the 21mm Elmarit ASPH. Â Beer drinker looking boy in the photo above. Â This is the stretching in the corners that the SA avoids. Michael Link to post Share on other sites More sharing options...
lct Posted May 10, 2016 Share #77 Â Posted May 10, 2016 You've lost me here folks: 1. DoF depends on focal length, aperture and circle of confusion. Nothing to do with symmetrical design right? 2. A lens with zero optical distortion shows a perfect circle in the corner, so no stretching there, right? 3. A lens with optical distortion shows an ovale instead of a circle in the corner, so stretching there, right? 4. A symmetrical design has less optical distortion, hence less stretching right? 5. So nothing new under the sun, right? Link to post Share on other sites More sharing options...
pop Posted May 10, 2016 Share #78 Â Posted May 10, 2016 I vote for #5. Link to post Share on other sites More sharing options...
michaelwj Posted May 10, 2016 Share #79 Â Posted May 10, 2016 You've lost me here folks: 1. DoF depends on focal length, aperture and circle of confusion. Nothing to do with symmetrical design right? 2. A lens with zero optical distortion shows a perfect circle in the corner, so no stretching there, right? 3. A lens with optical distortion shows an ovale instead of a circle in the corner, so stretching there, right? 4. A symmetrical design has less optical distortion, hence less stretching right? 5. So nothing new under the sun, right? Bingo. You're up to speed with the last few hours! Â But it's fun to get there though isn't it. What was this thread originally about? Something about 21mm lenses? :-) Link to post Share on other sites More sharing options...
rirakuma Posted May 10, 2016 Share #80 Â Posted May 10, 2016 Do you lose coupling below 70cm with the SA? I guess it doesn't matter too much with a 21 but just wondering. Link to post Share on other sites More sharing options...
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