My camera body has a small marking on one side, indicating the position of the image sensor. (The manual even makes a point of explaining that this mark exists, and what it means.)

What possible reason would I have for knowing this? Why would I care exactly where the sensor is? It's buried deep within the body anyway, so...?


Macro shooters sometimes need to know the distance between their subject and the image (film/sensor) plane, because that's how the minimum focus distance of a lens is measured. The mark gives you an easy way to determine whether you're inside or outside of that distance.


I often take images of file art for reproduction prints. Aligning focal planes can help eliminate distortions due to improper prospective. Both the target and image sensor should be parallel planes.

  • The marker seems way to small to accurately define a a proper line (let alone a proper plane). How do you use it? – xenoid Jul 26 '18 at 13:29

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