I am going to post my question here, before I go over to classic enlargers and ask Harry. I have an Omega D2 with the variable upper condenser, which I believe makes it a D2V. I recently fiddled with the bellows adjustment that controls the distance between the neg stage and the lensboard. This caused some vignetting when printing 4x5 with the 135 mm lens, which I have resolved by removing the upper condenser as you would with a 150 mm lens. My question is twofold: 1. What the heck is the name of that adjustment and control (it even has a scale)? 2. How do I dermine what value on the scale should be set to for any given situation? I suspect it is some combination of neg size, focal length and enlargement factor. Thanks in advance.