Two-dimensional color CMOS cameras have become ubiquitous. They promise to support ubiquitous spectrometry. When raw illumination levels can be measured by such cameras, their use for spectrometry depends on using as many pixels as possible and on being able to calibrate images at point-of-use. Stacked, mutually rotated transmission diffraction gratings provide a means to generate multi-order, wide dynamic range dispersed visible spectra suitable for absorption, reflection, and fluorescence spectrometry. The theoretical basis for dispersion, resolution, and normalization of such spectra are derived, and initial characterization is reported.