Increasing resolution and lower costs of off-the-shelf digital cameras are giving rise to their utilization in traditional and new photogrammetric activities, such as transportation, surveillance, archeological, industrial, and medical applications. This progress is enabling amateur users to generate high-quality photogrammetric products using such cameras. For most, if not all photogrammetric applications, the internal metric characteristics, usually known as the interior orientation parameters (IOP), of the implemented camera must be determined and analyzed. The derivation of these parameters is usually achieved by implementing a bundle adjustment with a self-calibration procedure. The issue of camera stability has been rarely addressed when dealing with analog metric cameras, since they have been carefully designed and built to ensure the utmost stability of their internal characteristics. However, the stability of digital cameras must be investigated, since these cameras are not built with photogrammetric applications in mind. We introduce two quantitative methods for testing camera stability, where the degree of similarity between reconstructed bundles from two sets of IOP is evaluated. The stability of nine amateur and professional digital cameras are checked over 8 months. The experimental result depicts the stability of the majority of these cameras.