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SID versus OID
Long SID and short OID mean less magnification and sharper edges.
The terms
SID is source-to-image receptor distance, measured from the focal spot to the receptor. OID is object-to-image receptor distance, measured from the part to the receptor. A third distance, SOD, is source-to-object distance, which equals SID minus OID. Together these set how much the image is magnified and how sharp its edges are.