The SB800 is more flexible and can support different TTL modes along with manual modes. So it can be used on a film body, an early digital body like the D1, or a modern digital body. But the SB400 is a stripped down consumer flash, it does not support the legacy TTL modes, and only works on more modern digital bodies, so it cannot be used with a film body.
Thank you for clearing that up for me.
Steve without the 'n'
Warning!! Handling a Hasselblad can be harmful to your financial well being!
Nothing beats a great piece of glass!
I leave the digital work for the urologists and proctologists.