bobbywise Posted January 30, 2015 Share #1 Â Posted January 30, 2015 Advertisement (gone after registration) Hi, Â Amongst some of my M-mount lenses, I have the Minolta 28 mm M-Rokkor and the Leica 40 mm Summicron-C. The 40 mm Summicron-C is very close to the 35 mm framelines, but brings up the 50 mm framelines by default. Similarly, the 28 mm M-Rokkor does not bring up the 28 mm framelines by default. Â However, I have realized that if I turn the 28 mm M-Rokkor a bit further (clockwise) past the normal mount position, the 28 mm framelines are activated. Â Similarly, for the 40 mm Summicron-C, if I install it so that is is not fully locked into the normal position, it brings up the 35 mm framelines instead of the 50 mm framelines. Â Would sliglighly overturning the 28 mm M-Rokkor have any negative effect on the bayonet mount and/or the IQ ? Â Would slightly underturning the 40 mm Summicron-C have any negative effect on the bayonet mount and/or the IQ ? Â Thanks for your expertise ! Â Rob Link to post Share on other sites More sharing options...
Advertisement Posted January 30, 2015 Posted January 30, 2015 Hi bobbywise, Take a look here Manipulating framelines by too much or too little twist. I'm sure you'll find what you were looking for!
lct Posted January 31, 2015 Share #2 Â Posted January 31, 2015 [...] Would sliglighly overturning the 28 mm M-Rokkor have any negative effect on the bayonet mount and/or the IQ ? [...] None that i'm aware of. Doesn't even prevent manual lens detection on the M240. Â [...] Would slightly underturning the 40 mm Summicron-C have any negative effect on the bayonet mount and/or the IQ ? [...]Ditto but there is a risk that your lens may drop this way. If you prefer 35mm framelines, you may wish to file the flange of the lens this way. Very simple indeed but there is no way of turning back so make sure that you don't plan shooting a lot of closeups before using your dremel tool. Also i would not do it for either M8.2 or M240 bodies whose framelines are not set the same way as other Leica Ms. Link to post Share on other sites More sharing options...
TomB_tx Posted January 31, 2015 Share #3 Â Posted January 31, 2015 Remember, the CL lenses have a ramped cam, so focus will only be ideal when properly centered with the cam. Over or under rotating the mount should have a (very) slight effect on focus with these lenses, as opposed to true M lenses with a flat cam. Link to post Share on other sites More sharing options...
Lenshacker Posted January 31, 2015 Share #4  Posted January 31, 2015 Hi, Amongst some of my M-mount lenses, I have the Minolta 28 mm M-Rokkor and the Leica 40 mm Summicron-C. The 40 mm Summicron-C is very close to the 35 mm framelines, but brings up the 50 mm framelines by default. Similarly, the 28 mm M-Rokkor does not bring up the 28 mm framelines by default.  However, I have realized that if I turn the 28 mm M-Rokkor a bit further (clockwise) past the normal mount position, the 28 mm framelines are activated.  Similarly, for the 40 mm Summicron-C, if I install it so that is is not fully locked into the normal position, it brings up the 35 mm framelines instead of the 50 mm framelines.  Would sliglighly overturning the 28 mm M-Rokkor have any negative effect on the bayonet mount and/or the IQ ?  Would slightly underturning the 40 mm Summicron-C have any negative effect on the bayonet mount and/or the IQ ?  Thanks for your expertise !  Rob  If the lens has an "Indexed Cam"- a cam with an "arch" cut into it, such as the 40mm Summicron: underturning or overturning the lens in the mount means the cam will not be properly indexed to the camera.  If cam of the lens is flat, such as on a Jupiter-3 and most LTM lenses: underturning/overturning will not cause a problem that I have ever seen. I do this for my "hacked" SLR lenses using a Fotodiox adapter. The adapters bring up the 35mm frames, and I use 50mm lenses with them.  Not a problem with this type of Cam:  minolta2  If the cam has an arch to it, the lens needs to be indexed with the camera, means locking it into place. Link to post Share on other sites More sharing options...
pfhrased Posted January 31, 2015 Share #5 Â Posted January 31, 2015 You definitely do not want to twist it too far past where it would normally go - doing that by mistake with a badly made LTM adapter meant the alignment of the rangefinder on my M9-P lost accuracy, and it had to go back to the fatherland for realignment. Link to post Share on other sites More sharing options...
bobbywise Posted January 31, 2015 Author Share #6 Â Posted January 31, 2015 Thanks guys ! Â I know about the flange mods, and planned to possibly have them done by a pro in NL (with coding). The last thing I want to do is mess up the focussing mechanism on the cameras, so for now I'll just use the frameline lever for now. Link to post Share on other sites More sharing options...
250swb Posted January 31, 2015 Share #7  Posted January 31, 2015 Advertisement (gone after registration) Thanks guys ! I know about the flange mods, and planned to possibly have them done by a pro in NL (with coding). The last thing I want to do is mess up the focussing mechanism on the cameras, so for now I'll just use the frameline lever for now.  Rather than devalue your 40mm Summicron you could perhaps have a look at this recent thread  http://www.l-camera-forum.com/leica-forum/leica-collectors-historica/361234-m2-40-cron-framing.html  Steve Link to post Share on other sites More sharing options...
bobbywise Posted January 31, 2015 Author Share #8 Â Posted January 31, 2015 Thanks Steve, Â I've seen various info about wedging the framelines lever in place. Â Rob Link to post Share on other sites More sharing options...
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