pico Posted December 30, 2010 Share #1 Posted December 30, 2010 Advertisement (gone after registration) I recently got a Nokton 25mm F 0/.95 lens and in the package was a special warning regarding focusing. It warned that focus magnification (if the camera has it) should be used because changes in temperature effect focus. Now I am wondering why I never had any such problem with the Leica M and fast lenses. Did Leica include some engineering in the RF to compensate? Has anyone had focus issues with the very fast Noctilux in cold or hot weather? Link to post Share on other sites More sharing options...
Advertisement Posted December 30, 2010 Posted December 30, 2010 Hi pico, Take a look here About Fast Lenses and Focus. I'm sure you'll find what you were looking for!
FrozenInTime Posted December 31, 2010 Share #2 Posted December 31, 2010 Fluorite elements ? Link to post Share on other sites More sharing options...
ho_co Posted December 31, 2010 Share #3 Posted December 31, 2010 Sounds like good marketing. "Some pictures may not be sharp. This is not a fault." Leica has been building lenses for a while, for the public, for NASA, for the military. Ask them why their lenses don't have the same defects as cheaper products. The answer is probably simply design and construction. Choose the right glass types for the job at hand. Choose the right metals to build the rangefinder linkages. "Why do your lenses work in hot and cold?" is a question I've never seen asked before; the answer would probably be more interesting yet. But then, maybe it's just, "That's why you buy Leica." Link to post Share on other sites More sharing options...
01af Posted December 31, 2010 Share #4 Posted December 31, 2010 I recently got a Nokton 25 mm 1:0.95 lens and in the package was a special warning regarding focusing. It warned that focus magnification (if the camera has it) should be used because changes in temperature effect focus. Now I am wondering why I never had any such problem with the Leica M and fast lenses. Because due to short focal length, high lens speed, and small image format, the Nokton 25 mm 1:0.95 is even more sensitive to small focus errors than any Leica M lens. Link to post Share on other sites More sharing options...
mjh Posted December 31, 2010 Share #5 Posted December 31, 2010 I recently got a Nokton 25mm F 0/.95 lens and in the package was a special warning regarding focusing. It warned that focus magnification (if the camera has it) should be used because changes in temperature effect focus. The warning doesn’t make much sense. On the one hand it is obvious that magnification should be used with a lens with these specs; this is a necessity even for slower lenses when used on an EVIL camera (which this lens is designed for). On the other hand, what has temperature got to do with it? On an EVIL body you just turn the focus ring until the image looks sharpest, and while the point at which you obtain maximum sharpness may vary with temperature, it wouldn’t really matter – since you are focusing the live view image on the sensor, if it is sharp in the EVF or display then the picture taken will be just as sharp. If a similar lens was employed with a rangefinder, magnifying the optical rangefinder image would be ineffective in combatting temperature issues. Once the lens and the rangefinder are out of synch, a perfect alignment of the rangefinder images would still produce unsharp pictures. Link to post Share on other sites More sharing options...
farnz Posted December 31, 2010 Share #6 Posted December 31, 2010 ... changes in temperature effect focus. ... Theoretically temperature change could affect focus because lenses are made of glass but the mechanisms for moving them are made from metal and the coefficients of expansion for glass (6 x 10e^-6 m/m K) and brass (19 x 10e^-6 m/m K) are different so brass expands and contracts with temperature change more, and more quickly, than glass. Realistically though, the range of temperature would need to be large and the rate of change of temperature would need to be substantial (say, freezer to heated living room) for there to be a noticeable effect and removal of condensation is likely to provide sufficient time for relative recovery. Also, as Michael points out, EVIL cameras for which the 25/0.95 is designed will be inherently immune owing to through-the-lens focussing. Pete. Link to post Share on other sites More sharing options...
pico Posted December 31, 2010 Author Share #7 Posted December 31, 2010 Advertisement (gone after registration) I remember from studying motion picture work that the high-end professional lenses were all marked with their actual focal length and micro-matched to the camera. They were short lenses like this one, and sometimes even faster (0.72). Perhaps the manufacturer was covering all possibilities. Maybe, just maybe CV is building M4/3 lenses to anticipate the growth of M4/3 video. Link to post Share on other sites More sharing options...
giordano Posted December 31, 2010 Share #8 Posted December 31, 2010 Maybe, just maybe CV is building M4/3 lenses to anticipate the growth of M4/3 video. Interesting thought. Does the 25/0.95 have a long focusing throw and a detailed accurate focus scale like pro ciné lenses? Link to post Share on other sites More sharing options...
pico Posted January 1, 2011 Author Share #9 Posted January 1, 2011 Interesting thought. Does the 25/0.95 have a long focusing throw and a detailed accurate focus scale like pro ciné lenses? It does have a long-throw focus. In my experience, most motion-picture efforts use add-on gears over the focusing barrel to control by motors which are, themselves, calibrated for follow-focus and so-forth. Regardless, modern micro 4/3 video cameras use live view, so such challenges are not so daunting. Of course, Leica has been releasing cine lenses this year. The mystery builds. What format has Leica targeted, and might they be suitable to a new line of Leica live-view cameras? You read it here first. Maybe. Link to post Share on other sites More sharing options...
FrozenInTime Posted January 1, 2011 Share #10 Posted January 1, 2011 It does have a long-throw focus. Does it ? The photos show infinity to 1m is about 20 degrees Compare to the scale on a zeiss CP lens Link to post Share on other sites More sharing options...
stunsworth Posted January 1, 2011 Share #11 Posted January 1, 2011 Of course, Leica has been releasing cine lenses this year. The mystery builds. What format has Leica targeted, and might they be suitable to a new line of Leica live-view cameras? Only if you think existing M lens are very, very inexpensive. I've had cold affect the rangefinder mechanism of my M6 in that the split images didn't meet. Link to post Share on other sites More sharing options...
farnz Posted January 1, 2011 Share #12 Posted January 1, 2011 ... I've had cold affect the rangefinder mechanism of my M6 in that the split images didn't meet. Steve, I presume that it was at infinity and rectified itself in warmer conditions (otherwise how would you know that the VF patch was off)? Pete. Link to post Share on other sites More sharing options...
stunsworth Posted January 1, 2011 Share #13 Posted January 1, 2011 Pete, yes that's correct. Link to post Share on other sites More sharing options...
hoppyman Posted January 1, 2011 Share #14 Posted January 1, 2011 Dear Pete, step away from the keyboard right now and no-one need get hurt! ......and the coefficients of expansion for glass (6 x 10e^-6 m/m K) and brass (19 x 10e^-6 m/m K) are different...........Pete. Link to post Share on other sites More sharing options...
pico Posted January 1, 2011 Author Share #15 Posted January 1, 2011 Does it ? The photos show infinity to 1m is about 20 degrees I have it right here in my hand. It focuses down to .17 meters, which is closer to 270 degrees full rotation. I understand that conventional mopix lenses will have more travel, but regardless, this is long. Regarding Leica making lenses for digital video ...uh ...uh ... never mind - at $22,000 USD each.... is that really correct? OMG! That's insane! Link to post Share on other sites More sharing options...
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