Hi Bob,

I tried both without and with zeroing in between runs and it didn't seem to make any difference. FWIW, I did much of my repeatability testing with the 24-105mm f/4 IS, since that's the lens I use most on the 5DII. Generally, though, the f/2.8 lenses gave the most consistent results (and had the tightest point spreads with a steeper curve.

Did you check the analysis info after each run? That avoids the known bug of it reporting no change needed when, in fact, a different value is optimal.