If you don't have a Samyang and want to use the dumb adapters with your electronically controlled lenses, there is an often described work-around to set the aperture. It goes like "Mount the lens to your camera, set the aperture, turn off the camera: Aperture will stay in position. Unmount the lens and remount it with the adapter." Some even recommend to set the aperture and unmount the lens without switching off the camera. I actually tried the first one with my 5D Mark II and an EF 1.4/50 USM. It didn't work (neither M mode with long-enough time exposure nor holding the preview button would work - the camera will simply reset the iris during shut down). The second one works, but is risky to the electronics. When using DSLRs you are dealing with hi-tech electronics. Both body and lens are equipped with chips to control all functions. Unmounting lenses during operation can't be recommended at all!!
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