@Michelle -

without extension tubes, for this test,

I wasn't planning on extension tubes of macro work -- just indicating how R/F could happen

normal

Aaaaahhhh, I love normal ... and seek it every waking moment.

DOF by changing aperture will effect color

I was thinking that changes in DOF within a scene or between
2 emulsions would affact our evaluation of color.

IOW, consider two shots of a scene made with 2 different
emulsions and therefore 2 different exposures ... If I use 2
different f/ stops, the out of focus areas will be different
and therefore harder to compare than if I keep the f/ stop
constant and vary the shutter speed.

But, how much would that (different f/ stops) affect our eyeball evaluation?

MGD