I'm embarking on a largish project which will include two different types of interior portrait. Before these new LF days I have been an exclusively natural light photographer, preferring to use faster film indoors and available light. So much so that I only know the rudiments of using flash. As my LF lenses are rather slower than I'm used to I'm looking into buying a small flash (probably a Metz 45) to blast a bit more light on my subject.

The first situation would be portraits on well lit interiors. think shopping mall well lit. There I would probably only need a small amount of fill, and is less of a problem. My second situation is home interior portraits. For these, even with the fast film, and even on the brightest day (here in London, there aren't that many of those), I would need to add some light.

I have two questions really. Firstly I'd like to have a relatively even exposure across the subject and the room. Obviously I can use a longer shutter speed to expose for the ambient light and control the flash with the aperture. I'm worried though, that the longer shutter speed will allow the subject to blur slightly around the blast of flash. Do any of you have experiencing balancing interiors like this and if so, have any tips?

Secondly, I'm wondering how best to soften the blast of the Flash. Do those clip-on diffusers do much in this regard? Or should I look into a softbox. Ideally I want a portable "window" of light. But that may be pushing it without a bigger set up.

I'm really keen on keeping the setup as simple as possible. Dragging a large format camera into a stranger's house will be intrusive enough and I don't want to have a massive lighting rig to go with it. I should say that I'm looking at shooting colour negatives (probably 400 ASA) using a Wista 45 field. Really I want a natural and spontaneous look, not rigid, upright sitters.

I'm going to start another thread in a minute too, about famous others' techniques. Kind of complimentary to this thread really as I'd love to know how some things are achieved.

Thanks for your help.