I have a H5D, but the question should apply across the board. Are there any favorite simple methods out there for blocking off the viewfinder to prevent light leaks with extremely long exposures? Is this really necessary with MF? I have only had an issue with fogging once or twice with long exposures (30+ seconds). My Nikon 810 has an eyepiece shutter, but no such thing exists for the H5D. One photographer I know simply puts his baseball cap over the camera.