To create a color image, a single exposure is taken, resulting in a sampling of only one of the primary red, green or blue colors at each pixel location. The two
un-sampled colors are then interpolated from adjacent pixels that have values for the color being calculated (note that the other colors do not contribute anything to the color being calculated).
construct a color RGB image from this sampling method, 66% of the intensity values must be calculated. Also note that the resolving element is the 2 x 2 Bayer Filter Pattern that was used to sample the image.
This means that an image captured by a 2048 x 2048 sensor actually has resolution of only 1024 x 1024. How does this happen? Envision that we create a perfectly small ray of red light that falls entirely onto
one red pixel with no other light falling on the sensor. What will the image look like? First, the red pixel that the red ray fell onto, will very accurately record its intensity value, and now the eight
adjacent pixels that had no red light falling onto them will each have a value of red light calculated for them due to the interpolation. The resulting image will actually represent the one pixel ray as being
nine pixel rays. Now imagine if our red ray fell onto a blue or green pixel; the resulting image would show nothing!
Other artifacts also result from this sampling method. Thin white lines and extreme
brightness transition edges in images can appear to have color stripes due to sampling and interpolation errors (see Figure 2).