Why is the background purple and not white ?

[Khaled]

Hello everyone.

As some of you may know, I just got my set of AlienBees strobes.
I connected the AB1600 into the octabox, the AB800 into a shot through ( thru ) umbrella, and the other AB800 isn't attached into anything ( acting as a hair light ), as shown below in the image.

I set my camera ( 350D ) into Manual Mode, Shutter Speed 1/200, Aperture f/8, and ISO 100.

I set the AB1600 into 1/4, the background strobe into its maximum power, and the hairlight into 1/2 as well.

I know that I need to read about 'the lighting ratio' if this term is correct, but at the moment my problem is that every time I take a picture, I get the background in grey/blue colour instead of the bright white ( I use white material background )

It'd be appreciated if you could guide me through the right steps to get my images as good as possible.

Thanks :)

The Image

http://img155.imageshack.us/img155/1927/img1300sy8.jpg

The Setup

http://img138.imageshack.us/img138/5063/lightingsetupoh2.jpg

[Emenresu]

you need to set a custom white balance with a grey card

[SkipD]

You need to get the white balance set correctly. There are several ways to do it.

The simplest thing to try is setting the white balance to daylight - that's the setting that comes closest for my AB lights.

For a studio setup, there are a couple of ways you can modify the white balance. One is to do a "custom white balance". Read your camera manual for this. The other is to shoot in RAW mode (which I would suggest anyway) and place a standard 18% gray card in the scene for one shot. When you do the RAW conversion, you can click on the gray card with an "eyedropper" tool and that process will determine the "color temperature" of the lighting. Then, just transfer that value to all the rest of the conversions (which can be done in a batch, saving effort).

NEVER try using AWB if you care about the white balance. It doesn't work worth a hoot in my 20D.

[mpoole]

I use the colour temperature setting on my camera when using studio lights. Start at about 5600K and some minor adjustments should get you there. Each light set is a bit different.

[joemoreland@cox.net]

If you elect to use a manual color balance make certain you obtain a "target" that is balanced for exposure and color. Kodak grey cards are accurate for 18% exposure settings, but not necessarily accurate for color balance.

[Wilt]

1. The color balance of the light, in combination with the camera's color balance setting, accounts for the off-color background rather than gray.

2. The light intensity on the backdrop, since it is inherently less than the light intensity on the subject due to Inverse Square Law of light falloff, is gray rather than pure white. Normally you need to light the background separately with another light, to get its intensity high enough to register white as white, without overexposing the subject. And to accomplish that you normally need more space between the subject and the backdrop.

[ccp900]

would it really be white balance or just the backgroud lights lacking enough juice to send it over 1.5 stops from primary subject?

what i mean is, your background lights should pop somewhere like 2 stops over the main light....you can try using 1 stop over then adjust if youre still not satisfied.

[chtgrubbs]

White background material isn't reflective enough to go completely white unless you put more light on it than on the subject. In Photoshop it takes just a few minutes to correct and balance. I did two Levels correction layers. The first I used the middle gray balance sampler to correct the background color. In the second layer I set the background to white using the highlight sampler. This raised the brightness of the toy, so I used a layer mask and masked out the toy so it would be unaffected by the brightness increase.

[Khaled]

Thanks again guys for you support..
I'll start reading about adjusting white balance in my camera.

Regards :)

[MrScott]

so I used a layer mask and masked out the toy so it would be unaffected by the brightness increase.


Great info, can you please describe "your" process for masking.

I've been messing around with channels, levels, hand painting and copying the selection to a layer mask, but it seems rather time consuming.

Is there an easier way???

Thanks...