hi,i was just perusing work by helen levitt and walker evans and realized that for a number of shots both these photographers used a mirror mounted to the front lens so as to photograph scenes at a 90 degree angle from where they were facing. i know there were such devices in the past for 35mm cameras and i believe also for some old graflex cameras. i am wondering if this could be possible with large format and if so if anyone has experience or suggestions regarding a