Abstract This paper presents a generalized version of the classic projective reconstruction theorem which helps to choose or assess depth constraints for projective depth es-timation algorithms. The theorem shows that projective re-construction is possible under a much weaker restriction than requiring all estimated projective depths to be nonzero. This result enables us to present a class of depth constraints under which any reconstruction of cameras and points pro-jecting into given image points is projectively equivalent to the true camera-point configuration. It also completely specifies the possible wrong configurations allowed by other constraints. We demonstrate the application of the theorem by analysing several constraints used in ...