A 70-200mm f/4L IS lens was used to test the static One-Shot AF performance of four 50D bodies that span both old (initial release date) and recent (as of 21Aug2009) production.

Regarding the AF test fixture, 18 inches on the ruler is at the plane of perfect focus. I've performed the same series of AF tests using my 400mm f/5.6L and the results are identical to that of the 70-200 f/4L IS. Yes, I'm very fortunate to have these two lenses (70-200mm and 400mm) that result in nearly zero AF error on all four 50D bodies (as also do as my 1DmkII).

What I find to be interesting is the near exact performance of four 50D bodies; this means Canon has come up with a camera design "and" manufacturing process that calibrates the 50D's static AF error to near perfection. From the standpoint of static AF performance it appears Canon has come a LONG way from the days of the 10D; back then the static AF performance varied considerably from unit-to-unit.

For anybody interested, here is a link (below) to a gallery that provides a lot more information regarding the static AF test fixture that I built and use. If the direct link doesn't work (they normally do not work on Pbase) just copy and paste the URL below to your browser's address bar and click on "GO".

http://www.pbase.com/jkurkjia/canon_30d