Recent developments in digital cameras in terms of an increase in size of the charged coupled device and the complementary metal oxide semiconductor arrays, as well as a reduction in costs, are leading to their use for traditional and new photogrammetric, surveying, and mapping functions. Such usage should be preceded by careful calibration of the implemented cameras in order to determine their interior orientation parameters. In addition, the wide diversity of expected users mandates the development of a convenient calibration procedure that does not require professional photogrammetrists and/or surveyors. This paper introduces a methodology for calibrating medium-format digital cameras using a test field consisting of straight lines and a few signalized point targets. A framework for the automatic extraction of the linear features and the point targets from the images, and for their incorporation into the calibration procedure, is presented and tested. In addition, the research introduces an approach for testing the camera stability, in which the degree of similarity between the bundles reconstructed from two sets of interior orientation parameters is quantitatively evaluated. Experimental results with real data proved the feasibility of the line-based self-calibration approach. In addition, the analysis of the internal characteristics of the utilized camera estimated from various calibration sessions revealed the camera's stability over a long period.