Weichold
Hello
It is possible to determine the effective speed of a film using a spot meter (i.e. by placing the film on a light table, positioning the spot meter and measuring the transmitted light). Is it also possible to convert these light values into density values?
Wolfgg
Hello Weichold,
Exposure values are on a base-2 logarithmic scale, whereas density values are on a base-10 logarithmic scale. One exposure value therefore corresponds to 0.3010D (= the base-10 logarithm of 2).
Example: You measure a difference in exposure of 4 between two points on the film. This results in a difference in density of approx. 4 × 0.3D = 1.2D.
Best regards, Wolfgang
