I believe the following description on the page http://en.wikipedia.org/wiki/Image_sensor_size is false: "However, the larger area does not imply a better low-light sensitivity or higher signal-to-noise ratio. While the light collecting area is larger, this is canceled out by the fact that the same total light from the scene is spread out over a larger area, that is, the light flux per square mm is lower, for a fixed aperture diameter. Larger sensors can still be advantageous for low-light applications because typically lenses for them exist with larger apertures than are possible for smaller sensors."

The following was my attempt to correct this information:

"A given lens will provide the same density of light on any sensor at a given aperture. For sensors with the same number of megapixels (MP), a large sensor will have proportionately larger pixels. The pixels on a 10 MP Full-Frame sensor will be more than twice as large as the pixels on an APS-C (2.3 times for Nikon, and 2.6 times for Canon). The larger pixel size is one of the reasons that full frame sensors typically have both superior sensitivity and reduced noise in low light in comparison to smaller sensors.  The smaller sensor is equivalent to a cropped section of the larger sensor but with smaller pixels, therefore much of the light from a full frame lens will fall off the edges of the smaller sensor and is "wasted." Theoretically, a 10 MP (Canon) APS-C sensor should perform the same as a 26.3 MP full frame sensor, all other factors being equal.

Although a given lens will produce the same depth of field (DOF) regardless of the sensor, in practice DOF is also affected by the sensor size. This is because at a given focal length the photographer must stand further away from the subject in order to frame the same shot when using a camera with a smaller sensor. Since the DOF increases with the focal distance (distance between the lens and the subject), a photograph taken with an APS-C camera will have a deeper DOF than the identical photograph taken with a full frame camera using the same lens and aperture setting. The photographer can alternatively select a wider angle lens for the APS-C camera and stand at the same focal distance as with the full frame camera to frame the same shot, however the DOF will be affected in the exact same way since DOF also increases with wider angle (shorter focal length) lenses."

However it was deleted with no counter argument or explanation of the facts. I believe my description was clear, but I will leave the false information in place as I see no way to make the explanation any clearer than this.

-Etienne B