Archived posting to the Leica Users Group, 2001/02/27

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Subject: RE: [Leica] Filter measurements with MTF
From: "Austin Franklin" <austin@darkroom.com>
Date: Tue, 27 Feb 2001 10:03:43 -0500
 
> MTF Measurememts on lenses with and without filters show:
> a drop in contrast of 1 to 2 % when the filter is of excellent
> quality. Such
> a drop is not visible in practice
>
> A drop in contrast around 10%, when the filter is of bad quality. Such a
> drop is clearly visible in practice. A drop of 10% is equal to the image
> degradation that you get when a lens element is decentred.
>
> Hopefully the filter discussion can be continued on a factual basis now.

Do you know what lenses and what filters, and do you have the actual
numbers?

Do you also have a description of the test(s)?