I understand mirror slap can introduce unwanted vibration. But what about the closing of the aperture ring, especially with a telephoto lens? I'll be using exposure delay mode with a tripod. When does the aperture ring close, when the mirror is raised or just before the shutter is released?

  • 1
    \$\begingroup\$ It may depend on the camera, but on my Canon 5D Mark III, the aperture closes when then photo is taken (even when on a timer delay), unless the Mirror Lockup function is on. When the Mirror Lockup Function is on, it closes when the mirror locks up. \$\endgroup\$
    – Mike Dixon
    Oct 31, 2017 at 17:25
  • \$\begingroup\$ It will depend on the lens. An entirely manual lens (without an auto-aperture mode) or a fixed aperture lens (such as a catadioptric) will not have any aperture movement and that is a sure-fire way to avoid the possibility of a problem. \$\endgroup\$
    – user50888
    Oct 31, 2017 at 18:14
  • 2
    \$\begingroup\$ as the aperture's mass is negligible, and it closes symetrically, it's extremely unlikely that its movement effects any vibration. \$\endgroup\$
    – ths
    Nov 1, 2017 at 20:27

1 Answer 1


It can conceivably vary by camera model and lens model, but for the most part most SLRs with mirror lockup stop down the aperture at the same time the mirror is raised. I've never noticed one capable of mirror lockup that didn't.

Many of Nikon's older SLRs (and some of their not quite so old DSLRs) use the same mechanical lever to drive both the mirror and the aperture control linkage, so the action has to be performed at the same time. Even cameras/lenses that have electronic aperture control normally do it the same way. My Canon EOS cameras all stop down the electronically controlled aperture via the servo motor in the lens at the same time the mirror is raised when mirror lockup is enabled.


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