I didn't think you could do this other than with the Restrained Life Viewer, but, by accident, I came across a Torley video that shows how it can be achieved with the conventional viewer (admittedly, it's a bit clunky, but it works).
If anyone's interested, it's at the end of http://vimeo.com/4268756
I've been wanting to make the light a bit softer in my home sim, this little flick explains a lot of stuff!