Quote Originally Posted by Ian C View Post
Here is what I think is happening. The light that passes through the back-illuminated negative radiates in every direction from the bottom surface. Some of it hits the 4 vertical sides of the square opening in the negative stage.

The edges are “lit up” and are slightly within the image pickup circle of the lens at the magnification that you’re using. Recall that the bands disappear at the corners. That’s because the image pickup circle is too small to include the corners.

The lens sees these bright bands and does what all good lenses do. It projects them faithfully onto the baseboard. I think this is the most likely explanation of your observation.

You can cover the edges of the opening in the negative stage with black tape to test the idea. If you cover them with black tape and the bright bands disappear, then you have positively found the problem and can easily devise a permanent fix.

The important things to realize are: there is nothing wrong with your enlarger or lens.

The projected bands, while annoying, are of modest intensity and are well outside of the image area. They won’t affect the enlargement quality and I don’ think they will affect the contrast of the main image.
Ian, Hats off to you for doing the thorough analysis. This makes total sense and I was getting suspicious of this late last night as well. I will try putting black tape around the perimeter of the opening in the negative stage just above the bellows and see if I can get rid of the stray light.

Am I missing something in the negative stage? How come others with LPL 6700 doesn't experience this?