canon 7D and 300mm f 2.8 combination problems

I posted this recently in another thread:

There is a really simple way to check microadjustment AF accuracy. No need for any software, or any setup. You can do it anywhere, anytime.

Put your camera+lens on a tripod and aim at a flat static subject. The subject should be perpendicular to the sensor plane. Brick walls, very distant tree/house/building, or even the moon will work. You can even do this from a safari vehicle.

Select single AF point (usually center AF).

Focus as normal with the AF point on the subject.

Turn on live view and zoom in all the way on the LCD on the area of the AF point.

Half press shutter button and see if the focus changes.

If focus changes, dial in some microadjustment and test again. In a few iterations, you'll get a feel for how much the adjustment moves the focus and you will converge on the best solution. All this will likely be faster than setting up an exotic test pattern that one purchases or using special software.

I have noticed that with my 300 f/2.8 +2x TC on my 1DIV that I need a little microadjustment when the temperatures are warm, but not when cold. So it is best to test on site.

Roger