HIGH ISO

[Brian]

Single point Auto Focus. Either in Continuous Focus Mode or Single Focus Mode. Meaning...you pick the AF point and the camera doesn’t argue / pick something different. With your Sony, even if you pick the AF point, if the camera finds something better to lock on (has more of a contrast swing) it will lock onto that, without you knowing. Hence the reason that the light over the Drummer’s head is in focus. 

Your Nikon lenses are ok but at 50mm and 28mm you are kinda limited. Give this a read:

http://www.dslrbodies.com/lenses/lens-databases-for-nikon/thoms-recommended-lenses-2.html