What is White Balance?
In a nutshell, white balance changes colour of the white tones in your photograph so that they appear white. This can often change the ‘temperature’ of your whole photograph, shifting it towards cooler blues or warmer yellow tones. This temperature scale is known as the Kelvin scale, and you can learn more about it in Ben Lucas’ in depth article, Hot Pictures: Better White Balance With the Kelvin System.
Quite often, an auto white balance set on your camera will work out fine. But if there’s something to skew your colours, like fluorescent or tungsten lights for example, or you’re pushing your image creatively, then you might want to make adjustments to offset this.
As well as choosing from white balance options within your camera settings (including the ability to choose manually from the Kelvin scale) you can also make adjustments while post-processing.
We’ll take a look at how you can do that in Adobe Camera Raw, here.
Adjusting White Balance in ACR
I'm going to demonstrate with this unprocessed image as it’s quite well exposed already but has definite areas of highlight and shadow, and larges blocks of colour so you can more easily see changes to the white balance.
Open your image in Camera Raw: drag it into your linked editing program like Photoshop or use ‘open with’ on the image after a right-click.
White Balance Presets
If you’ve shot in a compressed format, like JPEG, the only preset options you’ll have under White Balance are Auto or Custom. If you’ve shot in RAW, you’ll have similar options to those on your DSLR. I’ve done a quick demo of each so you can see the effects, first, Auto:
And here are each of the other options:
From top left to bottom right: Cloudy, Daylight, Flash, Fluorescent, Shade and Tungsten.
You can see each either warms or cools the image down to varying degrees. Their names are indicative of what’s being offset, so for example both Cloudy and Shade will be assuming darker, greyer days and so shift towards warmer tones.
Custom White Balance
You can choose a custom white balance in two ways. Either drag the Temperature slider along the (Kelvin) scale until you get the desired effect, or use the colour dropper tool on the top toolbar to select the colour you want the software to recognise as white or neutral.
In my example image, if I was to click on the light part of the clouds – which are my closest ‘white’ – then the temperature won’t shift much.
The idea is the software picks the opposite colour on the spectrum from the one you’ve chosen in order to make a balance. We can see that more clearly if I click on the green grass as my neutral:
You can see there’s a definite shift to purple. If I clicked on the blue sky, we’d get a shift to yellow/orange, and so on.
Understanding Your Histogram
While you don’t need to be able to read a histogram to adjust your white balance, you can get a better understanding of the whole picture by doing that, so it’s worth touching on here. In ACR you’ll see your histogram in the top right corner.
A histogram – the graphical representation of tonal values in your photo – might look complicated, but once you know what it is you’re looking at, they’re really easy to read at a glance – and very useful!
In your mind, if you split your histogram into three sections vertically, the furthest to the left are your shadows, the middle your midtones, and the right your highlights. How the information is displayed in those sections can tell you at a glance, without even seeing an image, how the exposure will be on a photograph.
Looking at my histogram, you can see the information is fairly nicely spread across the whole graph, but with most of the data grouped into the shadows and midtones section. We know that’s right if we look at the image – the photograph has few true highlights, just a few clouds. If we saw a large peak at either end of the image, we'd know that was a photograph with high contrast—dark shadows and bright highlights. Information mostly grouped to the middle would be quite a flat, or low contrast image.
If information is peaking too high (and in danger of clipping) at either end of the graph, then you might have an under or over exposure problem. On my histogram you can see one small peak at the far left.
Clipping Visualizations
As I have Clipping Warning turned on, ACR draws my attention to overexposure with red shading, and underexposure with blue shading. The peak to the left corresponds to the blue area we can see shaded on the image.
As a better example, if I drag the Exposure slider up so that everything is too bright, this is the result:
You can see from the histogram that the information on the graph has shifted right, towards the highlights and now large sections of the image are shaded red to tell me there’s a loss of information there – they’re just solid colour rather than genuine information.
Adjusting the shaded parts by sliding the Highlights and/or Shadows sliders will let you adjust this, but only so far as the information that was collected when you shot – so again, if your output is a compressed format, you’ll have less to play with than if you shoot in RAW format. Of course, it’s always best to get it as right as you can in camera.
Now you know how the exposure is distributed across the histogram, you can look at the colours (channels). They're displayed as RGB, with yellow, magenta and cyan appearing where they overlap and grey where all three (RGB) overlap.
Here's the histogram again. Looking back at my example image, it’s easy to see which channels are primarily making up the photo, where they’re placed and if they're close to being clipped.
If we look at the sky, it’s pretty obvious it’s blue. We know it’s also in the lighter part of the image, so we can ascertain from that that the blue showing to the right of the histogram is representing the information in the sky.
If I flip across the menu to the fourth option along, HSL (Hue, Saturation, Luminance) Adjustments, and choose Saturation, and lower the blue slider until it’s at -100, that would take all of the colour out of the sky, and we’d be able to see that reflected in the histogram on the far right—most of the blue is now in the shadows and has gone from the highlights (though remain in the cooler tones of the grass towards the left/shadows).
It’s an extreme example that you’d likely never want to replicate, but it’s useful to demonstrate how to read the information in a histogram and how changes you make, might illustrate. You can use the histogram to inform changes you make to your photo. For example, a picture with rich and smooth colours would have pixels distributed across each 'section' of brightness with a gentle fluctuation rather than jagged peaks.
In Summary
While it’s always best to try and get everything right in camera, it’s not always possible, or we can change our minds later and want something a little different. Adjusting the white balance in Adobe Camera Raw gives you plenty of options, whether that’s ridding yourself of an accidental colour cast, or just making small tweaks to get the look you’re after.
For most images, ‘auto’ will usually do just fine, with the occasional adjustment using the dropper or slider for a more refined result. Keep an eye on your histogram to help you understand what it is you’re doing when you manipulate the information available in your image, and remember, you can only move around information that has been captured, as soon as you start to push things too far in one direction or another, ACR and your histogram will certainly let you know about it.
If you'd like to learn more, and see some processing in action you can check out this video. It's for an older version of ACR, but everything still works the same way:
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