When
you photograph a subject that features a regular pattern of stitching or weaving,
a strange pattern of stripes unrelated to the original pattern in the subject
may appear in the shot. This is referred to as a moiré pattern. (Colors
may also appear in the pattern.)
A moiré pattern is a 2-dimensional "beat" captured by the camera
as a result of the interaction between the regular pattern on the subject and
the regular pattern of the CCD pickup element in the camera.
Moiré familiar examples of this phenomenon can be seen when two layers
of the green mesh used to shroud construction sites overlap, or when layers of
the lace curtain material used in homes overlap, resulting in patterns of stripes
at widely spaced intervals that differ from the spacing of the actual stitching
or weave in the fabric. The moiré patterns seen in digital images are
basically the same phenomenon.
Moiré patterns only affect digital cameras and do not occur in conventional
film cameras. This is because there is no regular pattern in the distribution
of light-sensitive material on conventional film. |
