Just got the cam yesterday afternoon.

I mounted a couple of Canon EF lenses but the iris button seems to do nothing, neither does pressing forward/back buttons.

Camera is set to Video/ProRes mode.

Am I missing something or is the camera not working properly? Lenses of course work perfectly on my 5D.

Ha!!!!!

Accidentally solved my problem.

Just as I was putting the camera down I seem to have touched the iris button and noticed a slight change in brightness of the display. So I fooled around a bit more and now I get it - you don't press and hold to change the iris, you sort of jog it - ie each press of a forward/reverse button makes a small instantaneous change in the iris aperture.

Never in a million years would have thought of that and the manual doesn't say anything except "Press the button"

Probably helps with battery life or something - but still seems pretty strange. Regardless - it works.

it's actually adjust using the fast forward and rewind button

I have problem with iris control too, i can't adjust the number, but screen doesn't change
i've tried 17-40, and 24-70 mk1

finally, i put a 70-200 mk2, and i can adjust my iris... so i think if the lenses are too old, they are not compatible on iris ontrol

I think you're right. I checked all my Canon lenses and the only one that doesn't work is the 16mm to 35mm. Which of course is the one that would work the best for what I do.

My 14mm works fine as does my 24 - 105. So I got an 18mm Zeiss and can now do 14mm, 18mm, 24mm - 105mm, which should take care of most of what I need.

I had thought of maybe selling my old 16 to 35 and getting a new one on the assumption that it would work OK. I might buy one and try it and return it if it doesn't work or sell the old one if the new one does work.

i think the Tokina 11-16mm f2.8 and sigma 18-35mm f1.8 are also good for it