Here, the delay results from the charging of the charge-coupled device (CCD) image sensor and relatively slow transmission of its capture data to the circuitry of the camera for processing and storage.
The comet-tail artifact that early CCD sensors suffered from was significantly reduced by the invention of the pinned photodiode (PPD).
One can either manually set exposure and focus, or use automatic exposure and autofocus, then fixing the settings so they do not change; this can often be done by holding the shutter release halfway down, or by using a separate "AE / AF lock" button (useful if taking multiple photographs that are not in a burst), and means the subsequent photographs will be taken faster.
Typically, prefocus + EFCS results in the shortest shutter lag (see the following individual sources with measurements for all available modi).
In the case of follow-up versions of cameras (Mark II, -N, -s, ...), it is usually save to assume identical performance unless explicitly stated otherwise in press releases or comparisons.