A current challenge for proteomics is detecting proteins over the large concentration ranges found in complex biological samples such as whole-cell extracts. Currently, no unbiased, whole-proteome analysis scheme is capable of detecting the full range of cellular proteins. This is due in part to the limited dynamic range of the detectors used to sense proteins or peptides. We present a new technology, structured illumination (SI) gel imager, which detects fluorescently labeled proteins in electrophoretic gels over a 1 000 000-fold concentration range. SI uses computer-generated masks to attenuate the illumination of highly abundant proteins, allowing for long exposures of low-abundance proteins, thus avoiding detector saturation. A series of progressively masked gel images are assembled into a single, very high dynamic range image. We demonstrate that the SI imager can detect proteins over a concentration range of approximately 1 000 000-fold, making it a useful tool for comprehensive, unbiased proteome-wide surveys.