LensAlign MkII Gen 4 is a precision reference tool that enables photographers to accurately measure and then adjust the Auto Focusing accuracy of their DSLRs. It also reveals the performance of the camera's manual focus system. A few years ago, photographers started to notice front/back focusing problems with their DSLRs. For example, when their camera's AF system was locked on a person's eye, the person's nose or ear was actually the sharpest part of the captured image. In order to allow hundreds of lenses and bodies to be interchangeable, the tolerances within the manufacturing process can cause any specific body/lens combination to potentionaly exhibit these front/back focus anomalies. To compensate for this condition, most new professional and enthusiast DSLRs have an Auto Focus Adjustment within their menu system. LensAlign was created as a focus system measurement standard by which photographers can accurately measure and improve the performance of their cameras' focus systems. Like its industry standard LensAlign PRO predecessor, the LensAlign MkII features our exclusive and patent pending True Parallel Alignment (TPA). TPA verifies perfect parallel alignment between the camera sensor plane and the target surface of LensAlign, a requirement for consistent and precise Auto Focus adjustment. LensAlign MkII comes standard with a 10.5 Focus Display Ruler containing 2 alternate display patterns, one on each side. A 24 Long Ruler add-on option will be available in early February. LensAlign MkII is shipped flat in a Priority Mail postal envelope to reduce shipping costs. The MkII can also also be disassembled for travel or storage. Note: Ships flat. Simple assembly required. (Under 5 minutes with no tools).