The crossword solution for the term F AS IN 'F-STOP' is FOCAL. FOCAL is an adjective that describes something that is related to a focus or center point. In photography, the term 'f-stop' is used to refer to the size of the aperture of a lens, which controls the amount of light that passes through the lens and affects the depth of field. Therefore, the term F AS IN 'F-STOP' can be answered with the word FOCAL.