Optiphot EPI: CF PL 2.5X projection to Canon EF sensor

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Since Nikon CF objectives are nominally free of chromatic aberrations,
these CF photo relay lenses are candidates for use in other microscopes which employ eyepieces without corrections.
Nikon made several revisions to CF PL optics.
@Scarodactyl compares several CF PL and afocal configurations in these EPI images.

Using a male M42-T2 coupling ring and M42-EOS AF confirm adapter with a bellows,
determined additional spacing wanted for Canon EF sensor parfocality:

about 6 cm (98mm camera flange to chimney top)

… implemented by helicoid and extension tube:

17-31mm M42 helicoid + 31mm EF extension tube

Magnification to 35mm sensor nearly matches parfocal eyepiece:

Canon 6D parfocal CF PL 2.5X … centering needs attention..

CFWN 10x/20 by afocal iPhone Se

As expected, APS-C sensor crops/magnifies:
Canon 90D parfocal CF PL 2.5X