Back Focus problem of Canon 5D Mark 3

[Kidboo]

Hi

I bought a canon 5d mark 3 recently and have coupled it with a Tamron 70-200 f/2.8 Di VC USD lens. I tested this for micro focus adjutment. My finding is that the lens and the camera are focusing accuratly when the setting is set to single shooting mode but continously back focusing in AI servo mode mainly at the telephoto end. I have done the testing in an ideal lighting condition and on a tripod with a self timer on. Any suggestion as to what is the problem and what need to be done to correct this.

Thank you

[Waddizzle]

I doubt if drive mode is making a difference. If it you say it focuses accurately in One Shot AF, then I doubt that AI Servo mode is back focusing.

[ebiggs1]

User error.  You did something wrong in your testing.  Redo it.