01af Posted November 5, 2012 Share #101 Posted November 5, 2012 Advertisement (gone after registration) However, if you look at post #3 and #6 there definitely is a different behavior. No there isn't; it's always the same. Of course, other flares, ghosts, reflections, or glaring veils may occur in addition to those symmetrical to the frame's center, and these other flares may be more noticable (i. e. brighter) than the symmetrical ones. Could you please be more specific what you mean by this in the sentence: All lenses do this. In each and every photograph taken with a lens, bright highlights within the frame will produce a dim ghost image of the highlight which is positioned as if the highlight was mirrored at the frame's center. Always. On any film or sensor. With any lens ... umm, wait—not sure about catadioptric lenses ... maybe these don't show this phenomenon, I don't know. Whether the ghost images of the highlights will become visible or not depends on the highlight's brightness as well as on how bright the area is where the ghost image will fall upon. If that's dark then the ghost will be visible; if it's bright then not (but it's still there). It seems the aperture also affects the ghosts' brightness—they're dim at full aperture and even dimmer at smaller apertures. So the phenomenon will appear most obviously in night shots where the lens is wide open and the better part of the frame is dark and a few highlights are extra-ordinarily bright. Link to post Share on other sites More sharing options...
Advertisement Posted November 5, 2012 Posted November 5, 2012 Hi 01af, Take a look here LEICA SERIE 5.5 NDx1 13026 GERMANY. I'm sure you'll find what you were looking for!
jaapv Posted November 5, 2012 Share #102 Posted November 5, 2012 On a catadioptric lens you will see the same phenomena, albeit distorted by the doughnut effect the lens produces. You are quite correct, however, the sensor surface is prone to produce additional reflections throughout the optical system. Link to post Share on other sites More sharing options...
k-hawinkler Posted December 6, 2012 Author Share #103 Posted December 6, 2012 No there isn't; it's always the same. Of course, other flares, ghosts, reflections, or glaring veils may occur in addition to those symmetrical to the frame's center, and these other flares may be more noticable (i. e. brighter) than the symmetrical ones. In each and every photograph taken with a lens, bright highlights within the frame will produce a dim ghost image of the highlight which is positioned as if the highlight was mirrored at the frame's center. Always. On any film or sensor. With any lens ... umm, wait—not sure about catadioptric lenses ... maybe these don't show this phenomenon, I don't know. Whether the ghost images of the highlights will become visible or not depends on the highlight's brightness as well as on how bright the area is where the ghost image will fall upon. If that's dark then the ghost will be visible; if it's bright then not (but it's still there). It seems the aperture also affects the ghosts' brightness—they're dim at full aperture and even dimmer at smaller apertures. So the phenomenon will appear most obviously in night shots where the lens is wide open and the better part of the frame is dark and a few highlights are extra-ordinarily bright. Looking again at the images and lenses used in post #3 and #6. There is no hint of a reflection in #6, even when increasing exposure by +5 in post-processing. To generate this type of strong reflection in #3 apparently requires two events: • First reflecting a strong point light source off the sensor • Second subsequently reflecting it off a lens element back onto the sensor. The lens used in #3 has a flat plate of glass at the front. The lens used in #6 doesn't, and apparently reflection off the other lens elements in negligible. In my view that's indeed a great difference in the practical use of those two lenses. Link to post Share on other sites More sharing options...
rscheffler Posted February 25, 2013 Share #104 Posted February 25, 2013 Hey, I realize this is an oldie, and you guys have whittled it down, but thought I'd chime in anyway. The problem is definitely a combination of the reflective nature of the camera's sensor and the flat front protective element of the lens. Obviously, as pointed out, this lens was developed in the film days when internal reflection was never an issue from the film itself. This is something that Canon has published about and that they recognized as part of their 1999 refresh for the super-telephoto lenses, all of which had front protective elements described as meniscus elements. Interestingly, in their recent super-tele refreshes, they've dropped the front protective element. From the link: Improving Compatibility of EF lenses to Digital Photography • Measures against flare and ghost particular to digital photography The image sensors in digital cameras have higher specular surface reflection than film. Due to this characteristic, when there is intense point light source within the field, the light reflects off the surface of image sensor, causing flare or ghost. To solve this issue, Canon has adopted a new approach to the optical design of EF lenses. • Adoption of meniscus lenses Most super-telephoto lenses have a protective glass at the front. When this glass has a flat surface, the light that reflects off the image sensor reflects back from the protective glass, occasionally resulting in spot-shaped ghost. To eliminate this phenomenon, all of Canon's large-aperture IS super-telephoto lenses adopt a meniscus lens shaped protective glass. The meniscus lens is spherical and has curvature with same direction on both sides. By employing the meniscus lens as protective glass, the reflected light from the image sensor forms an image in front of the image sensor, and then diffuses. The majority of the diffused light deviates from the image sensor, thus preventing ghost (see Fig. 4). But I doubt this would be a doable solution for the 280/4. First of all, it's out of production, but introduction of a meniscus front element would, I imagine, affect optical performance originally calculated with a 'neutral' front element. Good to see though that stopping down helps, if not ideal for night photography. Link to post Share on other sites More sharing options...
k-hawinkler Posted February 25, 2013 Author Share #105 Posted February 25, 2013 Hi Ron, Thank you so much for chiming in. I really appreciate that. I didn't know about Canon's work that you point to. Thank you, thank you, thank you. Technical Hall - Technical report 2003.8 Apparently, in this thread we came independently to the same conclusions. That's all the confirmation I need. I also would like to thank Robert_M again for his contributions in figuring out the operative mechanism. I really enjoyed the spontaneous long distance Forum collaboration with him and others, e.g. Lars. Ron, you made my day. Thank you. By now I have learned when I can use the Leica APO-R 280/4 lens to its advantage. And also when to avoid using it. Used appropriately that lens produces stellar results. But it ain't perfect! Link to post Share on other sites More sharing options...
k-hawinkler Posted April 2, 2013 Author Share #106 Posted April 2, 2013 Another relevant point about filters: http://www.l-camera-forum.com/leica-forum/2364535-post8.html Link to post Share on other sites More sharing options...
k-hawinkler Posted October 12, 2014 Author Share #107 Posted October 12, 2014 Advertisement (gone after registration) Another example. http://www.l-camera-forum.com/leica-forum/leica-m-type-240/349808-sensor-issues.html http://www.l-camera-forum.com/leica-forum/2800464-post2.html Leica Test - Louppls Link to post Share on other sites More sharing options...
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