Sorry if the list got a blank message from me a few minutes ago. The
computer just sent one off when I hit the reply button.
Anyways, to respond to George's comment below, I have a ROC 11x14 with
tapered bellows that can vignette (unless I catch it) because of the bellows
dimensions. It happens when the rear tapered folds of the bellows interferes
with the light path from the lens along the long dimension of the format. I
have to pull the rear folds forward quite a bit to avoid the vignette. This
occurs since I'm mounting the lens using an iris diaphragm mount on a lens
cone in order to get sufficient extension with an 18" lens. The bellows
extension track is only 15" . The rear element of the lens in this
arrangement is several inches in front of the front standard rather than
behind or near the front standard as it would be with a more typical
shutter/lens configuration. The light clears the cone but can hit the rear
folds if I'm not careful. This problem would not occur if I could extend the
bellows more with a longer track (not using the cone for the extra length) or
if the bellows were of a non-tapering design and the front standard larger.
Granted, it's a special case, but it is a problem related to the bellows
dimensions and the design of the camera.
Otherwise, I'd agree totally with George.
Joe
In a message dated 01/24/2001 7:29:47, [EMAIL PROTECTED] wrote:
<<Sorry Joe,
vignetting problem cannot come from narrow bellows at the front standard.
If the ground glass doesn't show "vignetting" when the front standard is
parallel to it (i.e. the image circle is sufficent to cover the ground
glass), it won't show vignetting when the front standard is tilted or
shiffted either. Sure, the image circle can come off the ground glass during
this action, but that is not vignetting caused by small bellows then - it's
just insufficient covering power of the lens. Vignetting only comes from
objects put in the angle of view in front of the lens.
Tapered bellows are used to allow smaller front standard when the rear one
is much bigger, that's all. George>>
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