Understanding camera lens and sensor compatibility When a lens is specified not just by its focal length, but also the sensor format for which it is intended, what compatibility limits does that place on the sensors it can be used with?
For example, if I have a CCD camera with a 1/3-inch sensor, must I use a 1/3-inch lens, or will a 1/2 inch lens (or anything greater or equal to 1/3 inch) do just as well?
If I took a pair of test images using a fixed camera and target scene, one image using a 1/3-inch 16mm lens and the other using a 1/2-inch 16mm lens, would the images be virtually identical to the casual observer? What differences should an expert observer see, if any?
 A: A lens intended for a 1/2 inch sensor should work fine. Camera lenses
normally produce a circular image called “image circle”, and you want
the diameter of this circle to be larger than the diagonal of the
sensor. In large format photography, it is quite common to have image
circles significantly larger than the imaging medium, as this allows for
camera movements.
It is also quite common, in digital photography, to use lenses intended
for a “full frame” sensor (meaning 24×36 mm), on DSLRs with smaller
sensors.

If I took a pair of test images using a fixed camera and target scene,
  one image using a 1/3-inch 16mm lens and the other using a 1/2-inch
  16mm lens, would the images be virtually identical to the casual
  observer? What differences should an expert observer see, if any?

They should be practically the same. The 1/2-inch lens should probably
deliver less vignetting. It
may also have slightly less resolution, as it is intended to be used
with a larger sensor, with presumably larger pixels. If the lenses are
of good enough quality, however, it will be hard to notice any
difference.
