I recently upgraded from D300 to D800 and I was very excited about the new auto ISO feature that automatically sets the maximum shutter speed based on focal length (including an adjustable multiplier). This is really convenient, especially for zoom lenses where focal length can vary rapidly.
However, it seems like when I attach a flash (SB600) that clever logic goes out the window. The flash shutter speed (option e2), which determines the maximum shutter speed while using flash, is a fixed setting buried in the menus and the smallest possible value is 1/60, which is not fast enough for a long lens. I can switch to Manual and set shutter speed myself, and auto FP (which can be enabled in setting e1) definitely helps since it only switches to high speed sync if I go under the flash sync time. But ideally it'd be nice if flash shutter speed were automatically set based on focal length using the same mechanism as auto ISO.
My main question here is:
what is Nikon's motivation for this limitation? And why can't option e2 be set faster than 1/60? Are there other vendors who do something more clever? The final question ended up being more like: what's an efficient way to shoot with flash on Nikon in situations where 1/60 isn't fast enough to freeze motion, e.g. when shooting a closeup with a long lens?