ltm adapters and rf focus

[Kozhe]

Hi everybody,

I got three chinese ltm-M adapters and any of my lenses is focusing correctly with them. All of them are back focusing more or less. Most of them are fsu jupiters but also a 35mm ultron and an old elmar 3.5.

Weird thing is... if these adapters are bad, it should affect the rf focusing also, isn´t it? I mean, keeping the lenses farther or closer to the film plane and focusing cam should affect both focusing on film and what you see through the rf patch in the same way, isn´t it? In other words:

You focus at one meter trought the vf. If the adapter is not that good the lens focus scale would be off, like 1.1 meters, but the image on the film should have the focus at 1 meter, matching what you see in the rf patch.

Am I just wrong as hell?

 

[ferider]

If the RF aligns at infinity, and all lenses back-focus (in particular Ultron and Elmar), the adapters are most likely fine, but the rake (?) of the camera RF is off.

Take the Elmar. Put the lens focus scale at 3m (or 1m). Take an object, a tripod with the camera, and put it at 3m (or 1m) distance from the object, measured with a tape measure. Now check the RF.

 

[Sonnar Brian]

If the adapter thickness is incorrect for focal lengths OTHER than 50mm, then the RF and actual focus will disagree. It's because the RF Cam of the lens does not move 1:1 with the optics. On the 50mm lens, the thickness should not affect the actual focus and the what the RF indicates. But unless you've used the Jupiters before with a screw mount camera or known-good adapter, the lenses could be off. Back Focussing is common for Jupiter lenses on a Leica standard camera.