The ergonomics are entirely different from the Yashica 124G I am used to. I've got the shutter release, shutter cocking, shutter speed, and focus knobs/controls down. Hopefully I'm just brain farting, but I can't figure out how to adjust the aperture to save my life! I have the manual from Butkus, but it shows a different lens. That lens has an aperture control knob...what am I missing?!

The only thing I can think of is to physically move the arrow that indicates the aperture. But it doesn't seem to want to budge and I don't want to force it until I confirm this is the correct way to adjust the aperture.

I've attached a picture of the taking lens...

TIA!