Fade in: Objects first appear at the same time regardless of HD, but with HD enabled, objects are fully faded in after 40% of the AR window (so on ar10 with 450ms, it's faded in after 180ms). Without HD enabled, fade-in time is a static 400ms.
Fade out: With HD enabled, objects start fading out at 40% of the AR window (so as soon as they're finished fading in) and finish fading out at 70% of the AR window. Sliderbodies start fading at the start of the AR window and finish when the slider is over.