[Leica] avoiding hood vignetting

[henningw at archiphoto.com (Henning Wulff)]

At 1:13 AM -0700 10/15/05, Bill Smith wrote:
>Does anyone know the optimum length/ depth of metal, straight-walled 
>49 and  55mm dia. hoods for 20, 24, 28, 35, 50, 85, 150, 200 mm 
>lenses with a  filter and step-up ring to get the max. flare 
>protection, but no vignetting? Is there a chart somewhere on the web?
>
>Thanks,
>
>Bill
>

Depends on individual lens designs. It's easy to figure out for 
yourself, by opening the film back, looking through the back of the 
camera with the shutter open on B and the lens wide open. Look 
through the lens from the back towards a bright surface such as the 
sky, sighting through a corner of the film gate. On the opposite side 
of the lens axis, slide a piece of cardboard parallel to the outer 
edge of the filter thread until you can just see the cardboard 
'darkening' the oval or lentil shaped bright area. Back off a few 
millimeters and that is as far as the lens shade can extend. Takes 
seconds, and works every time. This is the best and only foolproof 
way to check for vignetting due to lens hoods, filters, etc.

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    *            Henning J. Wulff
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