It seems as though by putting the paper down
on the easel first i was able to focus a little more
accurately. it's still not 100%, but it's better
-that's for sure.
I read that; the image printed more sharply. The plane for
better focus was lifted ever so little and placed more nearly
at the paper's surface. As I mentioned the paper's 'sees'
light we do not see. IF the enlarger lens is very well
corrected over a very broad spectrum including
the UV then the white light used for focusing
and any color the paper 'sees' are at the
same focus. BUT ...
If color correction is less than perfect then the focal
point of the lens for which the paper is sensitive can lie
above or below the visual focal plane. Because papers
especially VC papers have extended blue and UV
sensitivity mis-focus can occur. Off hand I'm
not sure where, above or below visual, lies
the blue/UV image.
You've tested focus on No sheet of paper print on one;
not so good. Now you've tested focus on one sheet of paper
print on one; better. My next test would be to focus on two
sheets print on one. Better yet? Go for three. If those tests
trend better it is obvious that the blue/uv focal point is
below the visual. Dan