EN12543 is a standard with the general title
Non-destructive testing – Characteristics of focal spots in industrial X-ray systems for use in non-destructive testing
This standard has been prepared by Technical Committee CEN/TC 138 “Non-destructive testing” (Secretariat: AFNOR, France).
The responsible German body involved in its preparation was the Normenausschuss Materialprüfung (Materials Testing Standards Committee), Technical Committee NA 062-08-22 AA Durchstrahlungsprüfung und Strahlenschutz.
First publishing was in the year 1999, in 2008 was an update done. In 2020 shall be the next update.
This thread shows the status of the standard in 2019.
EN12543 contains at the moment 5 different parts:
Part 1: Focus-Scanner method
Part 2: Pinhole camera radiographic method
Part 3: Slit camera radiographic method
Part 4: Edge method
Part 5: Measurement of the effective focal spot size of mini and micro focus X-ray tubes

The five methods are introduced in the standard:
"In order to cover the different requirements for focal spot size measurement, five different methods are described in EN 12543-1 to EN 12543-5.
The scanning method (EN 12543-1) is dedicated to those applications where quantitative values for the intensity distribution and spot size are needed, i.e. calibration and image processing purposes.
The radiographic methods (EN 12543-2 and EN 12543-3) describe the traditional techniques and are dedicated for certification purposes and for field applications. A digital detector not only provides focal spot length and width, but also the user with quantitative values for intensity distribution. The digital method may be used as a reference method as in EN 12543-1 *
Where no pinhole or slit cameras are available in the field, the edge method (EN 12543-4) may be applied. It represents a very simple method for field application.
For micro focus systems, see EN 12453-5.

*This text was added in the update of 2008

Please have in your mind that these standards measure the focal spot size only in the "center". The size and shape will differ outside of the center. For details, please read the post about the .