Sigma dock AF tuning

[Mr Badger]

I've recently bought a Sigma 100 - 400 contemporary zoom and plan to fine tune the AF as it's front focussing slightly at about 25 feet at 400mm. I understand how to fine tune at the relevant focal lengths and distances, except when it comes to the infinity position. Has anyone done this bit successfully, if so, what's the expert opinion on how best to achieve spot on focus at infinity, or to tell if it's front or back focusing at that sort of range?

 

[Brazo]

Don’t sweat infinity too much. Chances are the changes you make lower down (mfd for example) will also correct infinity.

To test infinity just aim at a building or sign that’s very far away and take a shot and then compare it to a live view shot. If the two images are close enough leave it as chances are when you focus at infinity it will be for landscapes or when manual focus or even live view focus will work fine.

If they aren’t the dial in some adjustments until the pdaf view matches the live view.