Gary is most likely correct:
> 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.
>
My statement "there appears to be no difference at different apertures" was
not based on actual measurements but on the appearance through the
viewfinder. The point I was making in relation to using the step-up ring
(hood) + filter still stands though.
Wayne Harridge
Ivanhoe, Victoria, Australia
http://www.geocities.com/Paris/Louvre/6152/
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