Nope, the measurement was NOT right; back to the drawing board - literally!
Did some further tests this morning and whilst the edges of the mask certainly do not appear in either close or distant focusing, what happens is that at full aperture, there is a clouding at the four corners which yesterday's test didn't reveal.
In yesterday's test, what was revealed was that unless the hood was placed in exactly the right place - parallel to the frame, obvious cutoff occurred - you could see the edges of the mask; however, that positioning resolved, at full aperture you don't see edges but you do see clouding, which is just as useless.
What surprised me too, this morning, is that taking two shots of the same blank, white interior wall, without any hood at all, the histogram varies when the focus is right on or moved right away... I'd have imagined that white is white, in or out of focus. I discount light loss due to extension, because the indicated exposure remains identical.
Any ideas?
Rob C
