User talk:GregDowning

Largest photographs in the world
Regarding your comment at Talk:Largest_photographs_in_the_world, you have a good point, GregDowning. With a 100 mm diameter lens, the resolving power for visible light is diffraction-limited to 2 arcsec or 9.7 radians for a full-colour image (or 1 arcsec for only violet light), corresponding to a spot of 7.4 steradians. As a whole sphere has only 4π steradians, there can be at most 1.7 distinguishable spots, i.e. 170 gigapixels. Unless an enormous lens or specialised image processing techniques are used, claims of 200+ gigapixels should be taken with a pinch of salt... (Note that the number of spots square with lens size, so a 1 m lens can potentially give 17 terapixels.) 86.30.200.63 (talk) 23:04, 22 February 2013 (UTC)