I have a few projection lenses that can be adapted for taking photos with. The catch is these lenses have no aperture control, so they can only be shot wide open. I thought that it should be possible to add an iris either in front of or behind the lens to overcome this problem.
In this article I'll share my results, comparing a lens with a built-in iris, placing the iris behind the lens, and placing the iris in front of the lens. But if you want the quick answer, if you want aperture control then you'll need to buy a lens with a built-in iris.
