Copyright © LightForm Inc, 2011 LightForm Inc: PARISS® Analytical Spectral and Hyperspectral Imaging Changes In Prism Bandpass Compensates For Falling Camera QE Providing Greater Wavelength Range Camera QE versus Prism Bandpass: The “Red” plot line presents the approximate QE of a typical CCD camera commonly used in many laboratories throughout the world.  The camera QE peaks around 460 nm and falls to less than 5% of maximum by ~900 nm.  The “Blue” plot shows how the spectral bandpass, and  resolution, of a prism increases at about the same rate as the camera QE decreases.  The “Black” plot line shows how diffraction grating bandpass also falls towards the near IR, thereby  exacerbating the fall in QE of the camera. Prism Benefit:  This means that a prism can operate over a wider wavelength range than a diffraction grating. The change in bandpass as the wavelength increases may be a problem for some applications, but if a signal cannot be detected bandpass has no relevance. Grating and Prism Characteristics