Experimenting bird close ups with the 600/5.6 = tube:
Both female and male with V1 + FT1 adapter + PK13 + Nikkor 600mm f5.6N ai-s EDIF + tripod, ISO 1600, f/8; ~4m of distance.
See that the rule - "push to the right" for better noise control in high ISO - definitively worked better for the female (above) than for the male, both at the noisy ISO 1600 of the V1 tiny sensor.
