Nikon D300 Complete Manual page 56

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between the "effective megapixels" and actual megapixel

count in an image that is produced: extra photosites along the

edges of the sensor array (white in the following illustration)

are there solely to provide data for the interpolation routine to

look at in order to calculate the pixels that end up at the edge

of your image (gray in following illustration):

Interpolation has several serious consequences:

Green data are the most accurate. Because the Bayer

pattern repeats green, the camera has more data from

which to make its guess. It also helps that the photodiodes

in the sensor are most sensitive to the green bandwidth.

Moreover, subtle differences in green values actually

make for larger perceived differences in colors, especially

skin tones (yes, there's some green value in skin colors).

Red and Blue data generate the most "noise." Since both

the red and blue photosites aren't repeated in the Bayer

pattern, there are fewer of those color data points from

which to predict each pixel's value. Worse still, when the

light hitting a red or blue photosite is low, noise becomes

a significant possibility in the photosite's value (see

"Noise," below). For example, you'll sometimes see noise

in the red channel of a blue sky, or noise in the blue

channel for a skin tone. Since the blue photosites are the

least sensitive to light, indoor lighting can be a real

problem for a sensor, as very small amounts of blue

wavelength light is produced by incandescent lighting,

Thom Hogan's Complete Guide to the Nikon D300

Troubleshooting