All:
Thanks for the useful feedback. Sorry I didn't correspond yesterday, but I drove from Hanksville, UT to San Diego county and was beat when I got home.
I ran a test as suggested by several of you. These photos were taken outside in bright sun at Goblin Valley.
Focused on a sandstone hoodoo in early afternoon. Bright sun, no clouds. Camera NOT on bracketing. Camera in Matrix Mode.
D800 with 24-120mm G ED zoom lens set to 124mm. This is the lens that came with the D800 kit. Ran 3 shots in A mode, f8, ISO400. Shot 1,2 in rapid succession and then third after 10 seconds.
Did exactly the same but set camera up in M mode. Set with f8, shows speed as 1/640, did not change focus or zoom setting. Results from EXIF file are as follows:
A Mode (800, 1250, 1000). M Mode (640, 500, 800).
FWIW I purchased this about 3 years ago as Nikon refurbished camera. It has had only modest use since work has kept me busier than I would like.
Comments?