Reason is as I was testing my used Canon EF Autofocus 35-70mm lens on my Canon 650 and the Canon Rebel, While looking from an angle into the inside of the lens to look at the movement of the aperature opening, I do not see it open or close when lens' Autofocus is set and the camera shutter clicked. Is the lens damaged or No good or Do these EF lenses automatically are supposed to be like that as the cmaera automatically set the shutter speed without having to adjust the aperature opening. I am not sure if my lenses are in good working condition or if they are damaged at this point. THANKS for your help. Of course the aperture blades should stop down. Perhaps you did your test with the widest aperture setting. Or you blinked at the wrong time.
Try again, this time on full manual, with an aperture setting of F8, and a shutter speed of 1/4. Look straight into the lens. Simple way to test would be to fix your lens on the rebel, select A mode, set the smallest aperture (f/16?) and then press the dof button. This should basically stop the lens down to the aperture setting set. If the aperture does not reflect this then the lens is probably not working. | 