Portraits - how to get a black background

crosmill · Mar 18, 2004

I want to know how to take portraits but with black backrounds.

i think you'd use extra lighting on the face and meter for that, but how many stops difference would I need to make the background compleatly black?

thanks in advance

voodoocat · Mar 18, 2004

Black you would want the background in zone 2. The proper exposure for skin is zone 5-6 so you would need to light your subject with 3-4 more stops of light.

crosmill · Mar 18, 2004

Thanks for the reply

I got the 3-4 more stops. But I don't understand what the zones are?

voodoocat · Mar 18, 2004

When I say zones, i'm referring to a scale of exposure zones from complete black to completely white.
Zone 1 is no shadow detail, zone 10 is no highlight detail. Zone 5 is middle gray (what your camera meter measures) So say your background is already black but you don't want the film to capture any texture and be completely black. You could take an incident reading and underexpose a stop. With a black background, a correct exposure would show detail since it's in zone 3.

crosmill · Mar 18, 2004

Thanks for that it's much clearer now.

I found an interesting article here http://www.srphotography.co.uk/srpzone.html that explains it in a bit more detail.

Can I just check I understand it. I want to expose plus 1 from the meter reading and I want the background to be minus 2 or 3 from the meter? Which would take the background into zone iii or ii and the subject into zone vi?

Have I understood it correctly?

voodoocat · Mar 18, 2004

Yeah it sounds like you got it! I forgot to mention in my scenario that after underexposing to make the background black you would want to need to add a stop more of light to bring the tone back up to natural. Of course, this is assuming you have some sort of studio setup.

crosmill · Mar 18, 2004

excellent! thanks for your help

Now I've got a basis, time for some trail and error............

Galaxy_Stranger · Apr 21, 2004

Howdy!

Are you using flash heads or Ambient light?
It helps to use a wide aperture and low-key your lighting if you're having problems. You have to make sure there's no direct light on the background.

Using flash heads pretty much wipes out a lot of ambient problems, depending on how powerful they are. This, of course, assumes you're not letting any direct sunlight in the room.

A paper background will bounce light back pretty easily. Other materials such as velvet and felt will absorb the light much better. Paper works just fine, though, and back-lit gels come out much better on paper than felt, IMO. When using, say, 2 or 400watt/second flash heads you're aperture is going to be smaller and the exposure time will be shorter, so the light bouncing back off the background is not going to be enough to bounce back onto the film and show up. (The background also has to be 3 feet or so behind the subject.)

P.S. - you don't have to over expose the subject, just under-expose the background. You ALWAYS want to meter for the skin, unless you're going for a specific effect.

P.S.S. - Yeah, he's right about the zone system. So, if you meter for the subject - that's zone 5 and you treat everything else in relation to the subject's exposure. (Keep in mind, this is portraiture.) It's all because film can't record the same range at one time the way our eyes "percieve" everything at once - "perfectly exposed". So, you're choosing which range of zones to use.