In some cases, the patterns can be even more subtle. For instance, imaging devices have special digital fingerprints. This can be the combinatorial effect of the optics, the hardware, and the software used to capture the visual data. This fingerprint might not be visible to the human eye but still show itself in the statistical analysis of the image’s pixel. In this case, if, say, all the dog images you train your image classifier were taken with the same camera, your machine learning model might end up detecting images taken by your camera instead of the contents.