After a bit of trial and error, I've just sucessfully set up the autofocus on my second-hand Focomat V35 enlarger. I thought that I'd describe the process which I used since other sources of information don't seem to provide much detail. As Tony Rowland mentioned in an archived post, setting the column height properly is the key to bringing the autofocus into calibration. It is necessary to readjust the column height any time one uses a different easel (or no easel at all). The scale units for the column height adjustment appear to be arbitrary, on my enlarger at least. The autofocus was out of adjustment with the column height set to "0" when using no easel and the correct column height adjustment proved to be 11 height scale units for my 5mm thick easel. I found this procedure to work well: (1) Set the column height to "0" scale units, place the easel on the baseboard, and put a grainy negative into the negative carrier (I used a strip of TMAX3200 film). Open the lens all the way (f2.8 on my enlarger). (2) Bring the enlarger head up to an enlargement ratio of 16 and, with a grain magnifier, bring the image into sharp focus. Set the focus ring detent at this focus. (3) Bring the enlarger head down to an enlargement ratio of 3. Unless you are very lucky, the image will be out of focus. Leaving the focus detent setting unchanged, rotate the focus helix to bring the image into sharp focus at the smaller enlargement ratio. Note which direction (left or right) it was necessary to rotate the helix to achieve sharp focus; best to write this down as well as the column height at that point. (4) Raise the column be about 5 height scale units. Repeat steps (2) and (3). (5) At some point, the direction of helix rotation for sharp focus at the enlargement ration of 3 will have reversed (now turning left when previous tries required turning right). When this occurs, you have gone through the correct height setting and the correct column height setting will lie between the last two column heights used. (6) Now reduce the column height slowly, checking focus at the enlargment ratios of 16 and 3 until you find the point at which sharp focus is obtained at both extremes without the need to readjust the focus. This should take no more than 20 minutes.