White balance questions?

Question

OK, white balance is something I've never fully grasped. I understand that for digital cameras, it's making some sensor adjustment to recognize what's really white, under the current lighting.

My questions are:

1) What is really changed by setting a white balance? Does it cause the camera's exposure meter to shift in some way to compensate, like being a third of a stop over/under? Or is it something else?

2) Does setting a white balance only affect shots taken using the cameras automatic exposure meter, or does it affect shots taken in manual mode, either outdoors on using studio strobes (which to my knowledge are color-balanced the same as daylight)? Would I only change the white balance if changing shooting conditions, like from direct sunlight to fluorescent or shade?

3) Do white balance lens caps work well?

4) Anything else I should know?

Thanks all!

Answer 1

White balance only tells the camera (if you shooting JPG and not RAW) what kind of light you are using.

To understand how it works do this:

a) set your camera to manual mode on a tripod and take a picture

b) don't make any changes to the camera, lens or tripod

c) try all the white balance options and shoot the same picture

d) download and compare all the pictures

You will notice they all look 'identical' except the light color will be different on each.

For the most part I use automatic white balance but when it is really difficult lighting or if I'm shooting products for Ebay or stuff like that then I use an ExpoImage disk to set my white balance.  I even use with off the shelf light bulbs :)

Answer 2

1) The in-camera software makes color adjustments when it creates the jpg file. In automatic white balance mode this happens to a varying degree for every shot. With a preset (sunny/ cloudy/ indoors), a custom white balance setting or a Kelvin setting, you lock in a fixed adjustment.

2) The white balance has no effect on the exposure.

3) I have no idea what you're talking about. If you mean colored filters - that was the way to compensate with film. With digital it's become a software adjustment and no filters are required.

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Aha, I looked up the term & learned something myself. I use the cover of my notebook as a white card. For personal use that's good enough and I'm lazy. When shooting jpg, it can be used to set a custom white balance and when shooting RAW, a picture of it can be used for reference when batch processing. A 5 minute Google search indicates that if you need to nail the white balance, the Epodisc is the preferred tool. Either way, a perfectionist would adjust the white balance for each new lighting condition.

4) The white balance setting only affects jpg files. If you shoot in RAW, you'll have to do color corrections in an image editor.