Background Question

[DavidS]

I would like to try using a background for some of my portrait shots. I will be using a shoe mount flash remotely triggered off camera. I would like to use either a white background or a black background. How do you fix the tendency of the whites to be a light grey and the blacks to be dark grey?

[pathfinder]

You can use a seperate flash or light for the background to add 1-2 stops more light to the background, than the subject, to drive the background to white. Or shade ( think gobos ) the background of all flash, to drive it to black.

Sidelighting with a single light that does not shine on the background and a black vinyl background yields this

http://Pathfinder.smugmug.com/photos/110870637-S.jpg

And a gray background with a second flash directed on the background yields this...

http://Pathfinder.smugmug.com/photos/46165984-S.jpg

[DavidS]

Thanks for the help Pathfinder. I am new to using lighting in this way. When you speak of a gobos are you refering to a devise which will focus the light on the subject?

[pathfinder]

I was describing a flag or opaque sheet that prevents light from shining on the background.. Barn door perhaps?

Wikipedia describes gobo as something that is in front of the light and creates a shadow - kind of like the bat ray that always called Batman:D

Wiki does mention further down the page the use of "flags" as gobos - opaque black curtains to create shadows - that is more in line with my use of the term I think.

Here is Wiki's take on the subject http://en.wikipedia.org/wiki/Gobo_(lighting)

The trick in capturing white or black backgrounds, is that they need to be at least 2 stops lighter than the subject, or 2 stops darker. That is where flags/gobos come in - to prevent the studio lights from shining on the background.

[DavidS]

Thanks Pathfinder. I had read the Wiki definition, but still wasn't certain what you meant. Your explanation makes it clear. Thanks again. I appreciate your help.