Hi Dawid, Iwert and all,
On 11 Nov 2009, at 3:52 PM, iwert bernakiewicz wrote:
> Hello John,
>
> I was just thinking, might it be possible that one of the elements is
> mounted the wrong way?
Could be. A long time ago, I "repaired" an old Vivitar 28/2 with oily iris
(On-Topic!!!) -- the iris ended working great, but it seems I mounted some
element the wrong way, because the only thing in focus is the centre :-(
From: Dawid Loubser <dawidl@xxxxxxxxxxx>
>Hmm - that's quite a plausible theory from an optics point of view,
>would explain
>why it could be sharp in the centre (where it never matters which way
>around the elements
>are mounted
Not sure if we could generalize that.
>Usually element separation is plainly visible.
What I always *thought* to be separation makes some rainbow-like surfaces on
some area of the lens group, starting always from the rim. But IME it
doesn't seem to make any noticeable difference in image quality. I once
tested a well worn, grossly "separated" Nikkor-O 35/2 against a minty one --
the separated one did perform a tad _better_.
But maybe I'm wrong. Anyone has a picture of what _should_ be lens
separation?
Cheers,
--
Carlos J. Santisteban Salinas
IES Turaniana (Roquetas de Mar, Almeria)
<http://cjss.sytes.net/>
--
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