Test series 1a with Sigma 17-50 / 2.8 OS HSM on a carbon stative
One Shot AF, Manual AF point selection, mean field
Result: 2 of 10 so sharp that I would be satisfied. The rest pretty much next to it, none of them extremely wrong.
Test series 1b with Sigma 17-50 / 2.8 OS HSM on a carbon stative
One Shot AF, Manual AF point selection, middle panel, dimmed f4.0
Result: all 10 images identical sharp. Not great, but the lens is also not great.
Test Series 2 with Sigma 17-50 / 2.8 OS HSM above the mean field
Result: all 10 images identical sharp despite open aperture
Test Series 3 with Sigma 17-50 / 2.8 OS HSM on a carbon stative
One Shot AF, Manual AF zone selection, middle zone
Result: 2 of 10 unacceptable, the rest could be worse, 1-2 of them halfway okay. Looking at the AF points used in Aperture to varies the 70D field between two elections.
Test Series 4 with Canon 100 / 2.8 Macro, f2.8 on a carbon stative
One Shot AF, Manual AF point selection, mean field
Result: sharpness at all acceptable, the images appear 7-9 "foggy", the rest sharp.
Test series 5 with Canon 100-400L @ 200mm, f5.0 (minimum)
One Shot AF, Manual AF point selection, mean field
Result: very similar images sharp, with good will two "outliers"
https://dl.dropboxusercontent.com/u/...ihen_CBaum.zip
Test series 6a with Canon 50 / 1.8 II,
One Shot AF, Manual AF point selection, middle panel, f1.8
Results: 20 images (10 am, 10 pm) reaches no useful sharpness. Aside from the basic blur the lens at the OB fails here the AF. However, there are a few "outliers", the result is uniformly bad.
Test series 6b
One Shot AF, Manual AF point selection, AF point above the central field, f1.8
Result: all 20 images comparable, slightly sharper than 1a, but not really good. Nevertheless, when using this AF field of the AF hits better and more consistently than in the middle field. Here again, 10 shots in the morning, 10 in the afternoon.
Test series 7
One Shot AF, Manual AF point selection, mean AF, f2.2
Result: minimally sharper than 1.8, with two wild outliers any way bad results
Test series 8
One Shot AF, Manual AF point selection, mean AF, f2.8
Result: 2 desert outliers in total lean sharpness, slightly better than OB, comparable f2.2
After that, I took my Sigma 17-50 / 2.8 again.
Test number 9, Sigma 17-50
One Shot AF, Manual AF point selection, middle panel, f2.8
Result: almost unusable sharpness. But this time at least no outliers, but lean throughout.
Test number 10, Sigma 17-50
One Shot AF, Manual AF point selection, AF point above the middle, f2.8
Result: very similar images sharp, no outliers, significantly better than in the middle field, consistently useful for a cheap lens.
Link to a zip with all the test series:
https://dl.dropboxusercontent.com/u/...6-10_CBaum.zip