Back in the day, a 35mm film camera (same size frame as a FF dSLR) came standard with a 50mm lens. That is because it produced a similar perspective as the naked eye. On a crop frame (DX) a 50mm is like a short telephoto producing a somewhat compressed perspective and is great for portraits but not so great for groups and general photography. The 35mm lens on a crop frame (DX) produces the same perspective as the naked eye just like the 50mm does on a FF. A 35mm on a crop frame is the lens I would choose if I could only take one lens on a photo shoot.