The color characterization of professional imaging devices typically involves the capture of a reference color target under the scene-specific lighting conditions and the use of dedicated profiling software. However, the limited set of color patches on the target may not adequately represent the reflection spectra found in the scene. We present a solution developed in collaboration with a camera manufacturer for the automatic color characterization of the sensors without the need of a physical color target. The optimal color transforms are computed based on the individually measured sensor spectral sensitivities, computer generated sets of color spectra forming a virtual characterization target and a mathematical model of the camera. The use of a virtual target enables the optimization of the color transform for specific image capturing situations by selective generation of the reflection spectra.