Collinear in Compur

[alexvaras]

Hi all,

I'm going to test this lens and I could attach it to a Compur shutter, the lens its a Collinear III f7.7 N5 and the Compur is f4.5.
Checking the ground glass at max aperture with the lens, I saw less and less light stoping down the lens aperture so my guess is even with the shutter attached, the effective aperture remains f7.7, but before doing the test I wanted to ask you what do you think about this.

Thank you for any help given.
Alex