why micro focus adjustment ?

I hardly ever use the lens at 70mm, and that's not where I need to eek out the best performance. It's at the 400mm, where I'm often cropping to as little as 10-20% of the frame, that I need the finest focusing I can get.

Not to worry too much, though... The following two images were shot before I started fiddling with the MA at all. This one was shot at 400mm, f/6.3, handheld, and cropped to less than 12% of the A77 frame before reducing for web:

and this one at 400mm, f/5.6, handheld, and cropped to just 7.5% of the full frame before reducing for web:

If you look at the eyes in both cases at original size, you can see why I was in no hurry to mess with the MA for the 70-400G

--
*Jerry*
Sony V1, H5, A350 and A77... Still learning...
'The camera is an instrument that teaches people how to see without a camera.'
-- Dorothea Lange
http://www.pbase.com/icicle50/root
http://www.pbase.com/icicle50/image/88943577/medium.jpg