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[OM] Re: chips on rear lens (e)lement of Z 21/3.5

Subject: [OM] Re: chips on rear lens (e)lement of Z 21/3.5
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxx>
Date: Sun, 12 Nov 2006 10:26:40 -0500
Maybe you've got it but I came to a much different conclusion based on 
its appearance and the fact that it appears in the same spot with two 
different lenses.

My guess is a dust spec on the sensor or some sort of artifact created 
by something in the optical path of the scanner that's scanning your 
film to make the prints.  Or possibly contamination on a roller or 
something that contacts the print during processing.

Even if the spot is on the negative you can't be sure it wasn't put 
there by the processing.  Try processing somewhere else.

Chuck Norcutt

Brian Swale wrote:

> Hi all,
> 
> I think I have figured out this little puzzle.
> 
> It was strange that the Zuiko 21/3.5 and 35~105 exhibited the same 
> phenomenon, when I was looking for a specific and different fault with the 21 
> only.
> 
> The phenomenon was paired hexagonal dark patches in areas of fairly 
> uniform colour.  Both lenses have six aperture blades.
> 
> I had decided to combine the test of the 21 with a scoping test of a local 
> land(sea)scape from a cliff-top for a panorama image. The shot was to be 
> right into the sun to see if the chips on the rear of the 21 would cause 
> flare, 
> and that's just where the sun was.  Since the shot was over sea from a cliff-
> top, there was ample plain colour in sea below and sky above, to show up 
> faults.
> 
> The paired dark patches are diagonally across the centre of the lens from the 
> sun position, and this is the clue to the origin of the phenomenon being due 
> directly to the sun. Of course in this position a lens shade is of no use 
> whatsoever. These patches did not show in either lens when I photographed 
> away from the sun. I don't understand why the patches show up as dark; I 
> would have thought lighter colour.
> 
> What has shown up is that both lenses are very resistant to flare showing as 
> patches of rainbow colour, but internal  reflections (paired in these cases) 
> incorporating the outline of the hexagonal aperture have left an impression 
> on 
> the image.
> 
> SO; conclusions: chips on the rear of this lens seem to have no effect on 
> image quality even shooting into the sun, AND both lenses are resistant to 
> flare anyway.
> 
> I had wondered if the sensor of the OM4 had been affected but now discount 
> that possibility :-))
> 
> Brian
> 
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