Starting out with printing here, I have a Durst M 600. It has a 50mm lens and I am trying 35mm negatives. I move the enlarger up/down I focus the lens up/down and the sharpest image I can get is not as big as l would like, the biggest I can get is about 5x8? I manage to print an 8x10 but the image is really out of focus. Am I doing something wrong? is the enlarger defective? the enlarger came in a box and I put it together myself, maybe I assembled wrong? Any advice or direction will help here, thanks! Jaime.