Focus film distance (FFD) is the distance between the X-ray source and the film in diagnostic radiography. It has recently been superseded due to the replacement of film with computed radiography or direct digital radiography detectors. There are now various possible alternatives: source to image-receptor distance (SID); focus image distance (FID); source receptor distance (SRD); and focus receptor distance (FRD).
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—bell hooks (b. c. 1955)
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