Kinds of vignetting to distinguish:
vignetting, micro lens
A kind of vignetting which occurs exclusively with digital cameras.
In many sensors above the pixels so called microlenses are located, trying to capture and direct the light towards the light-sensitive parts of the sensor surface. This is but only up to certain angles with which the light passes to the sensor (eg 12 degrees off the vertical axis ). This can vary from sensor type to sensor type.
Micro lens vignetting can be avoided by a lens with a small angle of incidence (CRA Chief Ray Angle). Optimal is an image-side telecentric lens.
Some manufacturers try to avoid Micro lens vignetting by micro lenses that are shaped differently on the edge of the sensor than in the center.
To use such sensors with image side telecentric lenses, will result in (maybe unexpected) micro lens vignetting.
Some sensors have built an electronic correction of vignetting! (especially SOC (System on a Chip).
Using the software you can get rid of vignetting by so-called shading correction. However, this correction costs computing time and you may lose image dynamic by this correction.