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Image/Sensor Size, and 645Z Focal Length and F-Stop Equivalence vs DSLR
See also Format-Equivalent Depth of Field and F-Stop in MSI.
This page discuses the equivalent focal length and depth of field considerations for the Pentax 645Z relative to a full frame DSLR or mirrorless camera.
Format equivalent focal length
The aspect ratios differ, so the question of focal length equivalence is open to debate. For some purposes, matching the same horizontal field of view makes the most sense, because most images are in landscape orientation, and the subject has to fit horizontally. Ditto for portrait orientation. The format diagonal doesn’t relate to those real world uses cases, yet oddly that is the convention.
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