The present paper realizes multiband spectral imaging with high spatial resolution for omnidirectional estimation of scene illuminant in a simple measuring system. To overcome the mirrored ball problems, we propose a multiband omnidirectional imaging system using a high-resolution trichromatic digital camera, a fisheye lens, and two color filters of commercial use. The spatial resolution of omnidirectional imaging systems is analyzed based on an optics model in detail. We describe a practical spectral imaging system. Use of the RGB camera with each of the two color filters allows two different sets of trichromatic spectral sensitivity functions via spectral multiplication, resulting in six spectral bands after two image captures with each color filter. An algorithm is developed on the statistical estimation theory for estimating illuminant spectra from noisy observations of the sensor outputs. The feasibility of the proposed method is examined from the viewpoints of spatial resolution and omnidirectional illuminant estimation.