Originally Posted by glbeas
I know it is a pain, and making the head is not acruate enough.
In your preferred neg size, take a piece of fogged and processed film,ei. black, like the leader in a roll of processed film, before frame number 1.
Scratch 2 lines diagonaly on the emulsion side, with a needl,e or a sharp tool (not a scalpel), do not go through the film, just the emulsion.
You can then easily centre your neg in the negcarrier.
Enlarge this in your enlarger, lens wide open, do not use easel.
you will see a white cross on the baseboard focus as best
move your enlarger head adjustment until best focus is obtained in all corners,
With a ruler and a marker, copy the cross on the baseboard.
Your enlarger is then aligned.
After using your enlarger to correct the perspective, all you have to do is put in the neg with the cross
and match it to the cross on the baseboard.