Yesterday I downloaded FoCal Pro to calibrate my new 5D3. It was an utter pain trying to focus by 600mm on the centre of the target using my cheap Manfrotto tripod, and we don't have concrete floors etc. The repeat runs were somewhat erratic. Today, I adapted the FoCal system to work under suboptimal conditions, which I recommend. First, find a sturdy cardboard box the size of A4 paper or its US equivalent.
1. Print the Reiken target, and glue it to the face of the box.
2. Put a screw or a nail in the side of the box at about 2/3rds of the height at the back.
3. Rest a ruler with horizontal lines facing you so it slopes towards you at about 30 deg.
4. Focus on the Reiken target. Shoot a couple, and vary the AFMA so you see when the line level to the face is the best in focus.
The results were within the spread of the semi-automatic method using the program.