Re: [Leica] how can the 75 Lux focus go bad?

[Gilbert Plantinga <gilplant@earthlink.net>]

For a CoC of 0.033mm:

DoF Near = 0.6964m
DoF Far  = 0.7036m
Total    = 0.0072m

All according to a little Mac program called f/Calc. I don't remember where
I downloaded it.

After this discussion began a few weeks ago I tried my 75 'lux out against a
tape measure, and sure enough it was consistently off with all 3 of my
bodies (M4, M6.72, M6.85). I called Sherry and told her that it wouldn't
focus up close, and about hearing (on the LUG) that Leica would calibrate
the lens to a specific body. This didn't sound right to me - the damn glass
should work on ANY M body - and she agreed. She asked me to check it out
wide open at a 'true' infinity (=>3 miles). When we finally got some weather
where the visibility was 3 miles :( I did, and sure enough the focus was off
at infinity too. It lined up perfectly in the rangefinder patch, the photo
was just way out of focus. She'll have the lens back to me in a couple of
weeks, I hope.

Gilbert
 
> I trust the man with the 13x19. I always choose reality over the internet.
> What would you estimate the critical depth of field to be at .7m and f1.4?