one LTM to M bayonette mt.adapter that can be adjusted to bring selected frame line

[xayraa33]

How hard can it be to make an LTM to M mount bayonette adapter that can be adjusted to activate the frame select lever inside the mount to one of three positions selected by the user?
Sort of a one size fits all, or one adapter for any VF frame line desired.

 

[drewbarb]

Pretty hard, actually. Take a look into the left-hand side of the lens mount of your M camera; now actuate the external frameline selector lever, and watch what moves in the mount. It's a tiny little piece buried in there. Assuming you could build a movable tab on the mount of an adapter, there's still only 1mm of material into which you would have to build a lever or something to shift position. Take a look at a Tri-Elmar lens to see how complicated a mount it would have to be- now imagine that in a LTM adapter. Looks doubtful to me.

 

[Roger Hicks]

Hard enough that it's not worth the effort, expense or inconvenience. Easier to add click-stops to the frame preview lever. Always assuming you want to cripple your M-series and reduce it to Bessa-R viewfinder functionality with manually selected frames.

 

[jlw]

Actually you can do this with ANY LTM>M adapter. Just press the lens release button on the camera body and gently twist the lens back and forth; you'll notice that it brings up the different framelines as you twist it.

The reason this works is that the frameline selected is determined by a simple angular relationship between a lug inside the lensmount and the latch recess milled into the back side of the lens' mounting ring.

I suppose it would be possible to mill three different recesses into the back of a ring, so that you could bring up the different framelines depending on which one you selected when you attached the lens. But (as you will have discovered if you actually tried the experiment above) the tolerances would be very tight, because it doesn't take much twist to shift from one frameline to the next. That would mean it would be very easy to select the wrong frameline accidentally, or to have them shift during use.

So, yeah, it could be done... but as Roger says, hardly worth the inconvenience.