This standard is based on the but there are some improvements:
- beside film also digital technique is allowed (CR and DDAs or radioscopic detector)
- recommends to use a proper E2002 Platinium duplex wire as edge
- takes the influence of SNR into account and
- gives a formula for optimal magnification M:
. . . . . . . . . . Moptimal = 1 + 1.1*SNR(P/ Soptimal)
. . . . . . . . . . with S = focal spot size; P = pixelsize; SNR = unattenuated Signal-to-Noise ratio outside the object
- calculates the unsharpness "Klassens-conform" from 2* (50% -> 84%)

- uses the correct formula for calculation of the focal spot size

- provides a statement on the repeatability

If you have the choice - use the ASTM version for measurement of the effective focal spot size of your µ-focus tube.