If anything, this has been one of the most least understood (and downright enigmatic) element in the cosplay community. As far as I know, its been a self-named category to differentiate itself from other "normal" photographers.
So what is a Cosplay Photographer?
On the outside, and probably the most obvious, is that its a group of photographers who concentrate more into photographing cosplayers. There has been a growing number of photographers posting their photos on their multiply accounts. Some were praised, others were criticized as being "improper" on their subject selections (and some more critical instances, their focus on certain body parts).
