Un-mounting lens while stopped down

Hi!

I'll be working on a film set this weekend and we'll be using SLR lenses on our camcorders.

The problem with EOS lenses is that the aperture is only controllable electronically;
so in order to use the lenses at smaller aperture, I will have to set the aperture on the camera, press the 'Preview DOF' button and detach the lens to keep it stopped down.

I'm only wondering if this practice could be harmful to the lenses in any way.

thanks!

It'll be just fine :)