Wednesday, March 9, 2005, 8:31:40 PM, Tom wrote:
TC> I don't quite understand that either... except that if dust is on the
TC> sensor, and the light hitting that portion of the sensor is not in sharp
TC> focus to begin with, it may tend to obscure the dust.
The dust isn't on the sensor, it's on the glass that's in front of it.
There is some difference in distance between that and the focal plane
itself. There is the glass, perhaps combined with antialiasing filter,
then the microlenses, then the colour filter array. With shallow depth
of field, the dust isn't as much focused as with big depth of field.
If the dust was exactly on the focal plane, it would be always in
sharp focus. But it's not. It's like with fisheyes - they have so much
depth of field that you can almost get dust speckles on the front
element in focus ;-)
Good light!
fra
