Test conducted to see if my EF 24-70mm f/2.8L is indeed backfocusing.

First 6 shots are taken with the lens at f/2.8, f/4.0 and f/5.6, at 24mm and at 70mm. What do you think? Magenta dot on number '8' on keypad in 100% original image is the focusing point.

Last 2 shots are taken with EF-S 18-55mm f/3.5-5.6, f/4.0 at 28mm, and 55mm. Cyan dot on number '8' on keypad in 100% original image is the focusing point.

Any ideas if it's the camera or lens that is backfocusing. All images are 100% if loaded at original, big file size. Please advise.