On the Personal IAS, how are graininess and mottle computed? What is the methodology employed?
Graininess and mottle are both measures of non-uniformity. Simply put, both graininess and mottle are the standard deviation of reflectance values within the area being measured by the instrument. If, in the unlikely event, every point in the image has the same reflectance value, then both graininess and mottle are equal to zero. The difference between graininess and mottle is the size scale or tile size used in the measurement. The mottle computation averages together all of the reflectance data within tiles that are 250m x 250m square. The mottle value is the standard deviation of these tiles values. The graininess computation averages together all the reflectance data within tiles that are 42m x 42m square. The graininess value is the standard deviation of these tiles. However, graininess excludes reflectance variation on a size scale larger than 250m. The math describing this process is defined in the ISO standard number 13660.
Related Questions
- On the Personal IAS, what color filter and density standard should be used when measuring graininess and mottle of different color patches?
- On the Personal IAS, is the graininess and mottle computation according to the ISO-13660 standard and methodology?
- On the Personal IAS, what are the measurement units of graininess and mottle?
