Buy article online - an online subscription or single-article purchase is required to access this article.
research papers
Given a photograph of small crystals, it is often desirable to determine the face indices. This paper describes a straightforward iterative method, incorporated in a computer program, by which the azimuth and polar coordinates of the optical axis of the photographic camera are computed from: the lattice parameters a, b, c, α, β, γ; the assumed indices of the three faces intersecting at a point; and the angles between the zone axes to which the faces belong, as measured in projection on the photograph. This optical axis is required to satisfy two conditions: it should be consistent with the assumed indices, and it should be constant with respect to intersection points throughout the photograph. Using these conditions as a criterion, one can eliminate the uncertainty in the assignment of face indices.