On another blog, I wrote a post about Gaussian blur and what it actually means. This is a pretty widely used function in Photoshop, so I thought it would be useful to describe what's actually going on at the pixel level. Rather than repeat all this, I'll just include the link:
That other blog, by the way, was sort of a precursor to this one, so I may refer to it from time to time, but more often, I'll rewrite and repost any good stuff here.
The Next Step
6 months ago