Smartphones are attractive instruments for low-cost spectroscopy because they incorporate at least one megapixel image sensor and are embedded in a high-performance computing device, with connectivity, a familiar user interface, a standard software environment, and the ability to add key metadata to spectral data. Several research groups around the world are exploiting all these capabilities to bring colorimetric- and fluorescence-based clinical assays to low-resource areas, and there is also activity in the use of smartphones for "citizen science" and educational purposes. Now, a key advance in the field of "smartphone spectroscopy" is presented in the paper “Standardized spectral and radiometric calibration of consumer cameras” by Burggraaff et al.

Although colorimetric assays have been demonstrated, some key problems have remained—questions regarding the accuracy and precision of the spectroscopic data and what processing is done by these devices before we can get hold of the data. In general, the cameras’ hardware properties are not disclosed by the smartphone manufacturers, and it is left to those performing "teardowns" to uncover this information. This paper gets to the fundamentals and presents a standardized methodology and database for spectral and radiometric calibrations of consumer cameras. The authors did find linearity in the RAW, but not JPEG, format data, although limited to 8-bits, but also found that results in general varied widely among cameras. In addition, the spectral response varied among the cameras, especially in the long wavelength cut-off of the R filter in the RGB Bayer set.

This is a thorough piece of work and is highly recommended for all those seeking to use smartphones, and other consumer cameras, for spectroscopy.

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