Upload & Sell: On
There is a hint of truth to this.
Image sensors have an angle known as the "CRA" or Chief Ray Angle" that is the maximum angle that light can cleanly enter the photo-site. Although a much greater issue in small imagers like cell-phones, it does apply to early, front-lit sensors. The outer edges of the image circle provide by some lenses is coming in at significant angle and might exceed some sensors' CRA.
Newer BSI imagers suffer less from the problem since the photo well is less deep.
+1 as well
this is also the reason why the Leica M9 sensor has special micro lenses on its sensor to compensate for this (to redirect the angle light especially in the corners) since the lenses are more tuned to the more tolerant medium known as film.
the micro-four thirds are designed from the ground up as "digital" for the same reason as well...
but, again, as Fred has said...this becomes less of a problem with newer sensors, so those "designed for digital" lenses are becoming more and more of a marketing hype.