A variety of multi-spectral imaging methods are discussed for acquiring spectral information from a scene. We first review conventional multispectral imaging approach. The conventional imaging systems are mostly constructed by multi-band imaging devices with different filtration mechanism at the sensor side under passive illumination. We show some imaging devices, estimation algorithms, and applications. Recently, active spectral imaging attracts much attention as promising technology. The active spectral imaging method has the possibility of recovering spectral reflectance information and estimating tristimulus values of object surface in high speed. We introduce a spectral imaging technology by synchronizing a programmable light source and a high-speed monochrome camera. Two effective applications to spectral reflectance recovery and tristimulus imager are described.