Originally Posted by RalphLambrecht
correcting perpective with an enlarger is the same principle as correcting in camera, except that the subject is the negative, and the image your easel.
You correct the perspective by changing the angle of each plane; 1-the negative plane, by tilting the enlarger head; 2-the baseboard plane (if not available on your enlarger, use a piece of wood); 3- the plane of the lens, which would spread sharpness over the whole image.
All planes must meet at the same point. Hard to describe in words, but if you follow the rules of the schimpflung effect as described for large format cameras, these rules are the same for enlargers.
Look up the manual for Durst Laborator 138, it has these adjustments