Originally Posted by Joe O'Brien
Thank you very much, this has made my decision rather clear. do you know what the 18mm extension tube between the lens and the body would do for image scale?

Joe
I'm assuming the lens focal length is indeed 80 mm, not 81.6 or something like that (which it usually is - never the exactt nominal focal length).

With the lens set to infinity, 18 mm of extension added, the scale is about 1:4.4, i.e. the smallest field of view will be about 25 cm square.

To calculate the scale and field of view with the lens set to the cose focus limit, i would need to know the minimum focussing distance. Which i don't.
So i'll assume (as i have done earlier) that it is about 90 cm/3 ft, i.e. an extension of just short of 9 mm.
Then, with the extra 18 mm, the scale will be about 1:3, the minimum field of view about 17 cm square.

By the way: assuming that minimum focussing distance of about 90 cm, the scale will be about 1:9 , the minimum field of view about 51.4 cm square.
So there is a leap from a field of view of about 51 cm to one of about 25 cm when adding the 18 mm tube. A gap you could bridge by using a tube of 9 mm length (if there is such a thing for the SQ-A).