Fleet Submarine Periscopes

[LukeFF]

I want to know if I am understanding something here correctly about the periscopes used in fleet submarines:

The diameter of the exit pupil for both the attack and observation periscopes is listed as being 4mm. Now, if I'm reading the description of exit pupil diameter correctly, (such as from this link), the brightness of an image viewed through a lens will increase as the exit pupil diameter increases.

Now, with that said, given that both fleet sub periscopes had the same exit pupil, does that mean the brightness of the image was the same in both periscopes?