help with background?

[angeleyes]

hi I was wondering in anyone could tell me what lighting I need to use to get a completely black background behind a subject???? thank you!!!!

[jerrymeola]

It is not the type of lighting that causes the background to go black. It is the lighting ratio.

The light that hits the subject is the correct exposure and the light that hits the background is much less causing extreme underexposure on the background, i.e. black.

In a portrait setting indoors the artifical lighting can be controlled to illuminate the subject and avoid lighting the background. In addition the subject can be placed within 6-8 feet of the lighting and the background can be 18-25 feet behind resulting in a 2 f-stop (3/4 of the total light missing) reduction in light. If the light on the subject is angled to totally miss the background then only the available light will illuminate the background and you may be 5-6 f-stops underexposed and get a totally black background.

Outdoors with flash your background will usually be much further behind the subject and the lighting ratio will usually give you a black background.

when this is not possible you can use editing software to select the background and darken it to the effect you want.