Coaxing a completely black background out of my portraits

[colin_miller3]

I am going to be doing some tests/portraits with T400CN, an Elan IIe, 50 and 85 f/1.8, 2 550EX wireless via the ST-E2 transmitter on light stands. I would like the dark colored background to all black but *just* black not past it. Should I externally meter the ambient and underexpose 2 or 3 stops? How bout choosing my aperture and shooting at 1/125th in manual mode?

[twmeyer]

Your concern should be with keeping spill light from the flash units

off the "black" background. (Black is Black, dude, unless you're

talkin' anti matter). Three stops down from midtone (zone V) is

minimum, unless "just" black really means dark grey. I mean do you

want tone in this "just" black or not? In which case you mean regular

plain ol' black, i.e. no tone, no detail (zone 2). Some African

American photographers in Atlanta have organized a group they call

Zone Three (Black, with Detail), which would indicate that 2 stops

down might be what <i>you</i> call "just" black. hmmm.<p> The best

way to keep your "artificial" light off the background, is to have it

(the background) a long way behind your subject and employ the old

inverse square law. If you have a short studio, like I do, use what's

called a gobo or flag to block the lighting on your subject off the

background. I use black foam core clamped to a light stand or black

"Cinefoil" near the flash itself. Cinefoil is like really heavy duty

aluminum foil and comes in black and silver, about 30$ a roll and

doubles nicely as a black jack (it's <i>really</i> heavy). Let me

also caution you against light in the lens, it will cause flare and

make solid (real not "just") black impossible. Use a good shade or

make a gobo for the camera, too. Have fun and lets see what you

get... t