A system and method for measuring a substrate edge signal for image sensor phasing. An intermediate transfer substrate edge signal can be effectively mapped by a substrate edge sensor and recorded for at least one complete revolution. A substrate edge signal from an inter-document zone sampled from any region of a substrate in runtime by a process sensor can also be recorded. A comparison or cross-correlation can be applied between the bare intermediate transfer substrate edge signal and the substrate edge signal sensed in the inter-document zone. A cross-correlation algorithm returns a maximum peak value when the two signals are registered in-phase with one another. This information can then be used to register the bare belt process sensor signal and the process sensor signal over the region of interest in-phase with one another. A flat-fielding algorithm can also be applied to the phase-aligned process sensor data to remove artifacts and compensate for substrate (e.g., belt) induced non-uniformities.