Plant life depends upon photosynthesis, which starts with absorption of light energy by the green pigment chlorophyll. The chlorophyll concentration in a leaf can be inferred from its colour.
PhotoFolia uses a colour standard and proprietary algorithms to provide a calibrated measurement of leaf spectral reflectance, from which chlorophyll and nitrogen concentration as well as SPAD value can be inferred. Photofolia allows users to select the particular plant species to give the best possible meausrment. Results are stored in the cloud, and can be viewed on a web browser at https://colourworker.com/apps/photofolia/showmeasurements