I finally did a bit of testing using a printed AF target this evening. I have settled on a AF correction of +2 and will try that for a while. the lens is basically bang-on but since the Af will tend to lock onto the front of any object one aims at, some of the available depth of field will actually be wasted in dead space in front of the target whereas I want as much of the target in focus as possible. My new setting will actually result in very slight back-focussing but it's deliberate and I will try it for a while. for small birds at close range it may work but I suspect it will trip me up on larger subjects and longer ranges.
Here's one of my keepers from the other day.
A little bit OT for this thread but Auto FP flash deserves mention... The fastest flash sync speed on D800 is 1/250th. At any higher shutter speed, there is no time at which both leading and trailing shutter curtains are fully open, so using flash at higher speeds would result in exposing only a strip of the image to the flash.
Auto FP Sync flash modifies the flash duration.....it makes the flash duration longer (and consequently weaker) by using "electrickery". The flash starts to light before the shutter opens and continues to light until after it has closed. This way, the entire frame can be exposed to light from the flash.
downsides of AUto FP flash : 1) flash exposure is much weaker 2) long flash duration does not freeze subject motion. with birds, if the flash startles them, its duration is now long enough to capture their reaction (seen this a few times).