How to check vignetting on a cut corner ground glass?

[electricphoto]

I am moving from shooting with a Linhof Technica and its full frame ground glass to a Sinar p. How do you check for vignetting on ground glass that doesn't show the corners? Any tips?

[Mark Sawyer]

When the camera is in position, the aperture is set for the exposure and while the shutter is open, check through the open corners to see if you can see the whole aperture. If you only see part of the aperture, you're in the "fall-off" area. If you can't see it at all, that corner will be blank.

[vinny]

The corners are missing so you can see the iris opening. If you can't, you get vignetting.
Otherwise, just replace the ground glass with one you like.

[Tin Can]

I like cut corners for a secondary reason, they release air pressure when opening and closing bellows and I IMAGINE that may prevent dust in the lens...

ymmv

[prendt]

I like cut corners for a secondary reason, they release air pressure when opening and closing bellows and I IMAGINE that may prevent dust in the lens...

ymmv

Indeed, it effectively sucks the air/dust mixture right into the bellows and on the lens.

[electricphoto]

Thanks all for the tip. I never thought about the dust effect. Thanks.