Archived posting to the Leica Users Group, 2001/11/02

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Subject: Re: [Leica] Rear element scratches
From: "Mārtiņš Zelmenis" <martin@lrpv.lv>
Date: Fri, 2 Nov 2001 16:55:56 +0200

I read all this with a certain awe. But then - do we put our lenses to such
tests that are really capable to show the harm that the peculiar <scratch>
does to our images? Maybe - if properly tested, under certain (different)
light situations those blemishes would <show their ugly face>?


Martin



Interesting question. And what is also interesting is the wide spread
belief that any ding, scratch, etc. on the rear element spells death to
a lens. I had a Nikon 28 1.4 - a magnificent lens, BTW, which I sold to
a fellow LUGER - with two scratches on the rear element. I never saw any
evidence of the scratches, even at 1.4, even in back lighting. I suspect
that the bottom line is that rear and front elements are far more
tolerant of our hamhandedness than we would ever belief. I also suspect
that IF one is going to have a problem caused by a scratch or ding, the
rear element is more likely to be the site of the imperfection.

B. D.

David Rodgers wrote:
>
> While reading some lug message from the last week or so I read some
> comments about scratches on lenses. While scratches on rear elements are
> probably worse than on front elements, placement of the scratch is very
> important. I had 150/4 Sonnar with a horrible scratch on the rear element
> (possibly left by a repair person gone mad with a screwdriver). It never
> showed up in the least (even at f4). The only time it was ever a factor
was
> when I bought and sold it. It greatly reduced the value of the lens. OTOH,
> I sold it for what I originally paid for it and I used it for 10-years.
> (try that with anything digital!)
>
> The horrific scratch on the 150 was on the outer third of the rear
element,
> which led me to wonder; in the mystical world of bent light and
> vectors,  just how much of a rear element is actually used. Maybe just a
> portion of the center? I suppose only a lens designer could answer that.
>
> Dave
>
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