Nikon D810: What You Need to Know
ISO 32 - 51,600 (sort of)
Although ultra high ISO sensitivity settings tend to get the most attention, for many photographers it's the D810's new 'base' ISO of 64 which is a bigger deal. Lower ISO sensitivity settings reduce the need for ND filters when shooting wide open in bright light or during deliberately long exposures like the image shown above.
For videographers, an extra lower ISO option is also hugely valuable since when shooting movies, you don't want to be changing shutter speed constantly because it greatly changes the appearance of motion in footage. As such, videographers don't have the option of simply using higher shutter speeds to compensate for brighter environments as stills photographers do. When shooting in 24p for instance the minimum shutter speed you can use while still getting attractively 'smooth' footage is ~1/50sec. With shutter durations much shorter than that, footage becomes fidgety and motion takes on a 'freeze-frame' appearance.
The D810's nominal absolute base of 32 (equivalent) is an extension setting and comes at the expense of reduced dynamic range, so we'd suggest using it with caution.