I think the neutral density suggestions were for gel type neutral density filters to choke the intensity of the flash units.
ah, okay!! never heard of ND filters for flash units..
Do you really want to shoot at f/2.8?
What exactly are these "non-digital" lenses? Why can't you stop them down?
well i love this lens.. it's a really old sigma lens that was build to fit the non digital EOS system (in my case the EOS650). If one tries to fit them on a digital EOS body (i.e. 400D) they will only work in AV or M mode (which doesnt bother me), though you can only use them with open aperture, namely 2.8! there's no way to stop it down, as you'll get an Error99.
Don't your strobes have adjustable power?
Yes they do, but I doubt that I can make them output so little power that I can shoot at f/2.8
But, did you get a kit lens like a 18-55 with you new Canon digital? If so just use that in the studio. Working with this lens at F/8 or F/11 with this lens will net optical quality far sharper than typically needed for images of human beings.
is it really? i have that lens lying around here somewhere, it's just that I thought I could use the Sigma as I really like it.
maybe just throw it onto the 650 body and leave it on there. for those times I will be shooting film...
//edit: I just tried it out. I can indeed reduce the flash power to make it so little that it will properly expose at f/2.8.. amazing 