Parallel back to parallel wall -- how do you know? OK, can't see this on old posts. I was shooting a window, I was parallel (back s tandard to wall in front) -- well now I suppose just a bit off. I can't see that close on the line on the ground glass. Is there something as objective as a bub ble level for knowing you are parallel? Measuring tapes wouldn't tell you becaus e the camera is only a foot wide. Maybe an orienteering compass? There must be a way? Thanks Dean