Tri-Elmar 28-35-50mm - automatic iris compensation?

[Dante_Stella]

Is it my imagination, or does the aperture open and close slightly as you change focal lengths? I imagine it would have to do this to maintain a constant f/4 aperture, and that's what it looks like it is doing.

Cheers
Dante

 

[Michiel Fokkema]

Yes,
Being a constant aperture lens it has to close the aperture a bit when going from 50 to 28.

Cheers,
Michiel Fokkema

 

[JNewell]

I had not noticed that - very cool!