The rationale for duplicating original aerial negatives in Alberta is investigated. Duplicating films produced by Kodak and Agfa are compared. These materials used in photographic duplication are `one step direct duplicating' films which produce a duplicate negative from the original negative. Kodak's duplicate negative has a typical greenish cast to the image, while the Agfa product is neutral. The contrast of the materials is markedly different, the Agfa PD1p provides a much higher reproduction contrast than the Kodak 2422. Both materials perform sluggishly in contrast changes with respect to development times. the sensitivity of the two products differs slightly. Exposure times are approximately twice as long with Agfa material. For short exposure times this difference is not crucial, but when long exposure times are required, the geometric increase in the differences can be significant. The spectral sensitivities of both materials are `blue sensitive' or orthochromatic. Interpreter evaluations showed higher preference from prints produced from the Agfa duplicate negatives rather than prints from the original negatives. Photogrammetric evaluations indicated that diapositives produced from the duplicate negatives were as acceptable as those from the original negatives.