Dual range cron compatibility

[wintoid]

I've got a dual range cron, which works fine on my M4. When I mount it on my M6TTL it also works fine, except that the focus gets very stiff just near infinity.

Does anyone know whether I'm likely to be damaging something, or whether there's something I can do to get it to work better on the M6TTL?

Thanks,

 

[furcafe]

I sold my DR Summicron years ago, & don't remember if I ever mounted it on my M6 TLL, but there may indeed be a compatibility issue w/the rear element hitting the light baffles @ infinity (when the lens protrudes the most backwards). I don't recall if this is a problem w/all M6 TTLs or M7s or only some of them.

There is also the separate problem of mounting the "eyes" due to the TTL being taller; that you can address by unscrewing the black spacing tab on the rear of the eyes.

 

[wintoid]

It's like it's fine at infinity, then stiff, then fine again by 10m all the way down to 1m. I haven't tried using it below 1m because of the eyes problem you mentioned, but at the moment I'm just trying to make sure I don't damage anything...

 

[maddoc]

I have just sold my DR Summicron but tested it before with my M6 classic. Focus goes smooth over the whole range but there was a resistance when trying to switch into the close-focus range. So it can be used without the googles down to 0.9m without any problem but the googles can't be mounted. I think it is related to the shape of the light baffles in the M6, which give a more rectangular shape compared with older Leicas (M4-P downwards), where the light baffles have a round shape.