You can measure...and level...and test your copy setup over and over again, but still not get crisp, corner-to-corner sharpness in your final image. This is especially true with the Better Light high resolution scanning backs. When viewing the capture at 100% resolution on the monitor, you witness the bitter truth of your focus attempts.
Any view camera body will have less than perfect alignment of the front and rear standards due to mechanical tolerances or age and wear from heavy use. The first step is to use a zig-align mirror system to check the camera for parallelism and make some minor adjustments with the tilt and swing movements. Next, use zig-align to help you position the camera parallel to your wall or copy surface accurately to assure sharp focus on all corners.
The ZV1 and ZV1.1 mirror sets will accomplish both steps, but will require some disassembly of the camera with each change of camera position. Zig-align, by a request from Better Light, developed the ZP2 Rapid Alignment plate which is identical in thickness, weight and balance to the scanning back. When it is necessary to change the camera distance, the ZP2 plate replaces the scanning insert in the spring back of the camera. Since the Ring Module is now on the outside of the camera, disassembly of the camera is eliminated and the re-alignment to the copy plane is fast and accurate.