This problem has me stumped, details as follows. LPL 7700 condenser enlarger 6x6 B&W neg printed onto 8x10 paper enlarger set up as per instructions: light bulb pushed to inner position top condenser removed 80 mm lens with reversed lens mount (i.e. 50mm lens goes in concave, 80mm goes in other way round) The problem is that one side prints unevenly, lighter than the rest. Please note it is not the corners but most of one side - the edge nearest to where we are standing to use the enlarger. The problem is not on the film - it was a well exposed & processed neg of a vase of flowers against a white wall. Wall tonality was quite even on the neg & this is what makes it so obvious when one edge prints lighter. I have seen something like this happen before when using small filters in the filter tray with a cardboard frame to hold the filter, i.e. the frame blocks some light. In this case we had a full size filter in the tray. But the problem looks similar to that, i.e. that something is blocking the light at one edge. For the life of me I can't see what it could be, wondering if this is something anyone else has experienced & overcome.