Re: Lens Variability

["marcober" <marcober@gate.net>]

Thank you very much. I hope sometime I can return the educational favor.
M. Berkley, Esq.

- ----------
> From: Charles E. Dunlap <cdunlap@rupture.ucsc.edu>
> To: leica-users@mejac.palo-alto.ca.us
> Subject: Re: Lens Variability
> Date: Monday, April 07, 1997 3:49 PM
> 
> >It might be helpful to us if you would elaborate on exactly how you made
> >the determination that the lens coating was flawed.
> >Also, if the flaws were not glaring, did it take much convincing of the
> >people at BandH to see the defects?
> >Thanks.
> >Mark Berkley
> 
> I looked at the lens! In normal room light I turned the lens (front and
> rear elements) so that the light caught the color of the coating. I
scanned
> across the surface of the lens and found spots where it looked like a
> bubble had formed and then burst. There may never have been an actual
> bubble there, but that's what it looked like. In other cases I saw places
> where specks seemed to be missing coating, as if it had flaked off. Both
of
> these defects were apparent by the lack of color: they looked like small
> mirrored spots.
> 
> Optically I'm not sure that the front element spots would have caused
> problems in most shots. The rear element defects worried me more. But
even
> if they wouldn't produce noticeable deterioration of the final image,
they
> leave me wondering whether the coating will be durable, whether it was
> applied correctly. In a lens that expensive I expect that the functional
> elements of the designe be in perfect order. I'm not as enamored of the
> exquisite engraving of the distance scale and such things that collectors
> prize, but lens coatings are fundamental the performance of the lens.
> 
> B+H had no qualms about accepting the two returns. I sent them back
> promptly, explained the problem, and requested an exchange. B+H has
always
> been fair to me. I have no idea, however, whether they returned the two
> imperfect lenses to Leica or sold them to someone else. I suspect the
> latter since the lenses did pass Leica quality control. Perhaps they will
> work just fine, but the three bad areas that I found on each lens nagged
at
> me.
> 
> -Charlie
> 
> --------------------------------------------
>               Charles E. Dunlap
>          Earth Sciences Deptartment
>           University of California
>             Santa Cruz, CA 95064
> Tel.: (408) 459-5228    Fax.: (408) 459-3074
> --------------------------------------------
>