jdlaing Posted January 21, 2014 Share #1 Posted January 21, 2014 Advertisement (gone after registration) What does the engraved red R and the red dot on the scale do? Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/220621-5cm-summicron-question/?do=findComment&comment=2514947'>More sharing options...
Advertisement Posted January 21, 2014 Posted January 21, 2014 Hi jdlaing, Take a look here 5cm Summicron question. I'm sure you'll find what you were looking for!
Leonil Posted January 21, 2014 Share #2 Posted January 21, 2014 From my work in Infrared photography that is the focus mark for IR light as it focus shifts. So if you are going to shoot IR, instead of, say, setting the infinity mark in the middle for normal work, you would shift the infinity symbol over the R or red mark to get correct IR focus. Link to post Share on other sites More sharing options...
menos I M6 Posted January 24, 2014 Share #3 Posted January 24, 2014 The tricky part is, that these IR focus marks on lenses are only valid for a very specific combination of IR-film and filter to be used. These do not necessarily apply to be used on a modern digital camera with modern IR filters (hence the reason, most lens makers stopped marking distance scales with these IR marks over the last decades). Nowadays, it acts mainly as a little reminder in which direction you have to shift focus and by about how much difference between different lenses but nothing more … It's a beautiful looking lens btw - rigid 5cm Summicron I suppose? Link to post Share on other sites More sharing options...
jdlaing Posted January 24, 2014 Author Share #4 Posted January 24, 2014 The tricky part is, that these IR focus marks on lenses are only valid for a very specific combination of IR-film and filter to be used. These do not necessarily apply to be used on a modern digital camera with modern IR filters (hence the reason, most lens makers stopped marking distance scales with these IR marks over the last decades). Nowadays, it acts mainly as a little reminder in which direction you have to shift focus and by about how much difference between different lenses but nothing more … It's a beautiful looking lens btw - rigid 5cm Summicron I suppose? So on a modern lens I could use that location as a starting point? Link to post Share on other sites More sharing options...
Michael Geschlecht Posted January 30, 2014 Share #5 Posted January 30, 2014 Hello JD, The Infrared Index Mark used to be put more or less where the F5.6 or F6.3 index point would otherwise have been on the depth of field scale. This is a guide for correcting for focal shift. Focus on the subject as usual (ie: 10 meters). Then move the focussed distance (ie: 10 meters) to the F5.6 position (or "R") on the depth of field scale by focussing the lens CLOSER. When the visible light point of focus distance (ie: 10 meters) has been moved to the CORRECT depth of field index mark for F5.6 (or "R"): Then the infrared (not visible) light is more or less in focus. Please note: Some lenses made by Leitz/Leica & some from other manufacturers have been corrected for both infrared & the visible spectrum. There is no need to adjust focus when using infrared sensitive materials with those lenses. Many mirror lenses, even some from many years ago, are corrected for both infrared & visible light. Best Regards, Michael Link to post Share on other sites More sharing options...
tobey bilek Posted January 31, 2014 Share #6 Posted January 31, 2014 So on a modern lens I could use that location as a starting point? Only to the extent the focus point is further left. The R worked beautifully with Leitz ir filter, close to 092 B+W, and Kodak ir film. I have done tests on the M8 and 092 and found the focus to be closer to 2.8 or 4. I marked the lenses with a red fine sharpie. Link to post Share on other sites More sharing options...
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