OK, need some help. Might be getting the 50mm f1.4 in 2 weeks and there is something I'm not sure about with regards to DOF (read a lot about it, but it doesn't seem to clearly answer my question). And after reading my question, you might not be so sure yourself!
If I'm in a large room or hall, with a group of persons on a stage (lined up roughly in a straight line), that is about 10-15m from where I'm shooting from (at f1.4), will I get significant blurring horizontally across the frame on APS-C or will people be reasonable sharp, i.e. does DOF increase relative to distance?
If my DOF is 1ft @ f1.4 from about 5ft distance from my subject, will it increase to say, 10ft @ f1.4 if I'm 50ft from my subject (using the same focal length, with my subject occupying proportionally the same amount of the frame)?
I ask because, I know DOF is the amount of the frame in sharp focus and that areas before the point of focus and after are essentially "outside" the DOF, but if I'm shooting a large enough scene that occupies the same relative area in the frame, could I assume that the DOF will remain the same?
Confusing, but I don't know how else to ask this question.