What is a Rangefinder Camera?

If you’ve spent any time reading about photography, you’ve probably come across reverential mentions of Leica cameras and other “rangefinders” used by a lot of great street photographers like Henri Cartier-Bresson in the mid-20th century. I know I was confused when I first heard about them since they aren’t really around anymore, so here’s what they are.
by Harry Guinness via How-To Geek