Archived posting to the Leica Users Group, 1997/12/29

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Subject: Re: [Leica] Importance of Coating Flaw?
From: Nick Hunter <nhunter1@mindspring.com>
Date: Tue, 30 Dec 1997 00:04:34 -0500 (EST)

From Jeff Moore's post:

>I'll have to go over
>this puppy with a fine-tooth comb, and see what a test roll reveals.
>
> -Jeff

To see if any trace of a coating flaw shows through, I'd photograph an
evenly lit, textureless medium gray card at the smallest aperture. The
smallest aperture gives the thinnest bundle of light rays to form each
point on the film. For this reason, any density variation due to a surface
flaw will be projected over the smallest area and therefore will be at its
most obvious.

At larger apertures, each point on the film receives light from the whole
aperture area and so a small flaw will be hidden.

Also test with light striking the front lens element for flare.

Nick Hunter