In sensitometry, use is generally made of logarithms to the base 10. Logarithms to the base 10 can be recognized from the generally written shortened form, lg or also log 10 . They form the basis of calculations in sensitometry . A minus sign indicates that the respective figure is a decimal fraction. In the Technical Data Sheets there are many examples to illustrate the advantages of giving sensitometric data in the form of logarithms.
Illumination is measured with a luxmeter.