Quote Originally Posted by polyglot View Post
That said, enlarger lenses tend to be very much of the older robust designs that are easy to manufacture. While there is some sample variation, they still tend to be diffraction-limited and with little lateral CA; the APO versions have reduced CA. Enlarger lenses are not ultrazooms and they are not complex. While I'm sure you can find an occasional Really Bad one, it's not common and not nearly as bad as the sample variation seen on the really complex new designs.
Real life example to demonstrate the point. I had inadvertently mis-seated one of the rear elements of a HM APO Componon during re-assembly. I'd say it was almost 0.5mm sideways. Six months later I decided to use the lens and was perplexed that the projected image was not side-to-side sharp after the laser alignment. I went and re-aligned the lensboard based on edge-to-edge sharpness with the Peak-1 magnifier. The results were surprisingly good and gave good prints during the printing session. To show how far off it was, laser beam needed to be about one centimeter off center to get the best print. Surprisingly all the prints (about 5x magnification) from the session were sharp, none needed to be re-printed.

My conclusion is that a significantly mis-centered enlarging lens can be used if one aligns the lens so all 4 corners are sharp with the Peak-1, rather than making the lens barrel perpendicular to the baseboard.