In Q.-Tuan Luong's "A step-by-step guide to operating the view camera" he mentions:

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# Check for vignetting (optional but recommended). This should be the last step before closing the lens, as vignetting might be due to lack of lens coverage or to obstruction by filters, shade, or bellows, and should be checked at taking aperture

* Through the corner cut-out of the groundglass look at your wide open lens: the aperture will look somewhat like a cat's eye pupil. Now slowly stop down until your the lens opening shape changes into a round opening in which you see all the aperture blades. This is the largest stop at which you will have no vignetting.

* Check top and bottom is you used rise/fall or tilt. check left and right if you used lateral shift or swing. * If necessary, straighten the bellows and take care of sag.

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I have an Ebony 4x5 field camera, and have been disappointed with some shots where some vignetting has ruined the corners of my shots. Unfortunately, my ground glass doesn't have the "corner cut outs" that might make determining whether any vignetting is occuring easier. When I am stopped down to a very small aperature, it is impossible to ascertain how much, if any, vignetting is occuring.

I take alot of pictures of buildings and structures that demand a lot of rise, which means that I need to push my lens close to the edge of it's image circle, but, of course I don't want to shade the corners of my film!

What can I do?