I am sure this question has been asked a million and one times before, but hopefully those of you who aren't ameteurs like me, don't mind answering it for a million and second time I have a 50mm 1.4 pentax lens, and was taking some portraits of my dad, and once I got them up on my comp noticed ALOT of blurring of his face. I had the aperature open all the way on most shots, and had a quick shutter speed and also I've had trouble with my diopter being off before, so I'm not sure what the prob is. So my question is, when you have your ap. set at say between 1.4 and 2.8..... what is the maximum distance you should be away from you subject??? Thanks to all who respond.