Light Falloff allows us to quantify the variation of light intensity along a flat surface in reflectance.
Light falloff allows us to quantify lens vignetting for different apertures as well as uniformity of illumination along a surface if we discount light falloff from lens vignetting.
The study of light falloff is essential before the capture of our charts, to ensure that the light falloff does not affect our chart in an uneven way causing errors when quantifying the OECF or Delta-e.
The fall of light has been represented by isolines, where red represents the average zone, green the zone of less intensity and blue the one of more intensity. The distance between curves is equivalent to a variation of 10 hp, so 5 isolines will be equivalent to a light drop of 50 hp along the image.
The statistics shown on the uniformity are:
- Mean: or average of the scene's pixels
- Dev: the standard deviation
- Max and Min: the maximum and minimum values of the scene
- SNR: the signal-to-noise ratio of the image.
- Non Uniformity: this is in relation to ISO 17957:2015 and indicates in % the lack of uniformity, the more value the more light drop