This tool calculates the unsharpness resulting from the change in source size, source to subject distance and source to film distance for radiographic exposures.

The formula for calculating radiographic unsharpness (or penumbra) is:

Radiographic unsharpness = Ug = f* b/a

f = source focal spot size.

a = distance from source to front of the subject

b = distance from the front of the subject to the film

From the formula given above, we can see that radiographic unsharpness can be reduced by:

1. Reducing the size of the radiographic source

2. Increasing the distance between the radiographic source and the specimen and

3. Reducing the distance between the specimen and the film.