Tips and tricks: Vignetting
by Stéphane Moniotte
The term vignetting describes the dark border appearing around the pictures when the size of the camera objective and the scope eyepiece are not strictly compatible. This can be avoided by using the maximal zoom offered by the camera, as shown below. For bird shooting, a simple rule: put the zoom in 3X zoom position and leave it there forever ! Most of us also use "Spot metering" as standard focusing choice and do not move from there.

How to avoid vignetting: on the left, a picture taken with the zoom at 28 mm; on the right, the same bird viewed with the zoom at 110 mm.