Measured Spectral Response Data
The figure below shows the spectral response of eight different photosensors:
For reference, the ideal response, standard photopic human eye response (CIE Photopic), is also shown. All eight products have similar shaped curves in that they are all broader than the ideal. Two products (photosensors
#2 and #4) have a much higher IR response than the others. Inspection of the photosensors revealed that no additional filtering was provided other than that contained within the photocell component. The similarity
of the curves is most likely due to the different manufacturers using the same types of photocell components. Additional filtering to limit the response bandwidth from about 470 to 625 nm would improve performance.