The technique is illustrated using blood as the target analyte, using bands of light centered at 395, 415, and 435 nm. Wavelength selection can either be by controlling the illumination (e.g., by using an alternate light source) or by use of narrow bandpass filters.

These latter conditions are more achievable by many 'mid-range' digital cameras.

However, acceptable results can also be obtained under many conditions if non-linear photographs are used or if only two wavelengths (one of which is at the peak maximum) are combined. Best results are obtained if linear images at the peak maximum, at a slightly shorter wavelength, and at a slightly longer wavelength are used. The combination of images is readily performed if the images are obtained with a digital camera and are then processed using an image processing program. If necessary, the photographs can be taken with different exposure times to ensure that sufficient light from the substrate is detected at all three wavelengths. This procedure works best for compounds with absorbance bands that are narrow compared with 'average' chromophores. The combination of photographs taken at two or three wavelengths at and bracketing an absorbance peak indicative of a particular compound can lead to an image with enhanced visualization of the compound.

Adobe image mixer