D800 Live View exposure simulation
This is my attempt to summarize and understand the exposure preview function in Live View, based on observations made on a D800E with the new 1.0.1/1.0.2 firmware. Please let me know if I am getting something wrong.
When in Live View mode, the function of the OK button (and other controls) will depend on the exposure mode.
In all exposure modes, toggling the OK button will show or hide the exposure compensation scale along the right edge of the monitor.
When using LV with A, S, and P exposure modes, the lens aperture remains at max (wide open). The monitor presents a simulation of the result that the Live View autoexposure system will produce for this scene. It is a simulation because the monitor image is not produced by changing aperture (or shutter speed, obviously), but by scaling the sensor output. If you toggle the OK button so that the exposure compensation scale is visible in the monitor, the simulated image will include the effect of the exposure compensation setting. When the OK button is toggled to hide the compensation scale, the compensation setting is not applied to the monitor display, but it will still be applied to your shot. Note that in A, S, and P modes, you can't change lens aperture to judge DOF on the monitor. The aperture dial and DOF preview button have no effect.
When using LV in M mode, the behavior is different. The lens aperture can be changed via the aperture control dial, so you can see its effects on exposure and DOF. But the DOF preview button does not work. The monitor presents a simulation of what it thinks your selected exposure settings will produce. The exposure compensation setting has no effect on the LV simulation, or on the exposure that will be used for your shot. Pressing the OK button just shows or hides the exposure compensation scale. The reading on that scale is the difference between your manually set exposure, and what the autoexposure system (including compensation setting) would use.
The simulated LV displays will not always accurately match your shots. Page 46 of the (English) D800/D800E User's Manual lists several conditions where the match may be wrong, including adjustments outside -3 and +3 EV, Active D-Lighting, HDR, bracketing, flash, etc.
Corrections and additional tips?