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Re: [OM] 18mm filters

Subject: Re: [OM] 18mm filters
From: PCACala@xxxxxxx
Date: Sat, 24 Apr 1999 13:02:23 EDT
Wayne writes:

> The lens does have a fall off in brightness (appears like about 1 stop
>  difference between the centre and the extreme corners), however this is a
>  normal phenomenon for an ultra wide lens.  There appears to be no 
difference
>  at different apertures.

I haven't measured what I'm subjectively grading as vignetting and it's 
falloff in f/stops, but I don't agree that improvement isn't had upon 
stopping down the 18mm f/3.5

Here are the vignetting grades I've noted:
Vignetting = C (f/3.5), B-(f/5.6), B+ (f/8), A-(f/11 and 16)

If anyone has a densiometer, I'd be pleased to have them measure four 
benchmark (A,B,C,D) slides for me.

Gary Reese
Las Vegas, NV

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