For all the things your camera can manage effectively without any human input - focusing and metering, for instance - there's still a lot it can't do. This is never clearer than when a set of pictures you felt great about at the time turn up on your computer looking indisputably wrong.
White balance is one such area - it's something photographers have grappled with since the days of film. At its most basic, white balance is when your camera decides what light temperature it's working with (which varies depending on your light source) and attempts to compensate for it.
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Even apparently consistent environments, like outdoor locations, can vary depending on factors like cloud cover and whether you're using a flash. If your camera gets white balance right, you won't notice it at all. If it goes wrong, you could get anything from a very slightly wrong photo to an image that bears no resemblance whatsoever to what you saw when you pressed the shutter button.
Incorrect colours, strange looking skin tones - even if the rest of your photograph is technically perfect, with the wrong white balance it will never look quite right.
Luckily, although the concept of white balance may be difficult to grasp, the ability to spot when it's wrong is a knack you'll pick up quickly, and you can correct it in seconds. Keep reading to find out how.
Choosing your shot
Unlike some editing techniques, changing incorrect white balance isn't something you can choose to opt out of. If it's wrong and you leave it that way, people looking at your images will notice that something's off, even if they lack the technical knowledge to describe it.
In the case of the shot above, the camera has chosen a white balance that is well wide of the mark, with the result that snow - which should, of course, be a neutral white colour - has turned light purple instead.
How much you notice incorrect white balance depends on your level of experience - you need to pay particular attention to images that contain people, because we're particularly sensitive to incorrect skin tones. Skin is something we see every day, so we notice very quickly when it's not quite right in onscreen photographs or prints.
That means looking for and correcting white balance should become part of your photographic workflow, in the same way as correcting colour curves or checking for sharpness.
If an image turns up with incorrect white balance, there are no two ways about it - you have to fix it, or people will notice.
What you'll need
Fixing white balance in your shots requires the use of a photo editor. The good news is that because cameras tend to get it wrong so often, virtually every photo editor can make the necessary corrections - often in just a few clicks.
In this instance we'll use Photoshop Elements, but the terminology and tools are standard: the colour picker tool also exists in Google Picasa, which is free and straightforward, as well as in GIMP, which is free, feature-packed and powerful.
Even online editors offer similar tools - Picnik.com, offered as part of Flickr accounts, has a white balance correction tool that takes seconds to apply. As ever, you'll get the greatest degree of flexibility from a tool like Photoshop or GIMP, but for simply correcting colour casts - where the whole image takes on an incorrect colour due to poor white balance - virtually any photo editor will do.
The only thing to remember is that the single-click approaches taken by free software need to be carefully monitored if you're intending to make expensive prints.
In truth, once you've got the hang of spotting incorrect white balance, fi xing it should take a few seconds per photo - it's important to trust your eyes when you're working on your images. You certainly don't need to carefully adjust your image to a precise colour temperature value.
Your eyes are only half of the equation, of course - you'll be looking at your shots on your monitor before you print them. If your display is badly calibrated, or you've never taken the time to find out whether it's set up correctly, you could accidentally make incorrect white balance corrections - or, worse, make changes to images that didn't need it in the first palace.
Before you start, it's worth comparing an image you've already printed with its onscreen version. If they're radically different it'll be worth checking your monitor before you embark on processing. Otherwise, working in RAW has its advantages, although you'll generally be fine even if your camera only shoots JPEGs.
You should consider saving a copy of every image you work on in a lossless format like TIF to preserve image quality. This doesn't apply in non-destructive editors such as Picasa or Adobe Lightroom, which don't change your original image.
How it works
Whenever you take a picture, your camera assigns it a colour temperature, which is measured in Kelvin. A candle, whose light glows orange, has a temperature of around 1,800 Kelvin. Daylight, which is generally more blue tinted, has a temperature of around 5,000 Kelvin. Other light sources - an overcast sky, an electronic flash, or fluorescent or tungsten lighting - have different colour temperatures again.
The temperature your camera assigns to an image is where the white point lies. This is the point at which something that should be white appears that way in the final shot. If the camera gets it wrong, something that's a neutral shade of white in real life will appear to be the wrong colour, looking either too blue or too orange in the shot. Everything else in the image will be too warm or too cold as well.
If you're fixing an image that contains people, the best approach is to look for skin tones and change the white balance settings until they look right - it should usually be easy to tell when you've got it right. If you don't have people to use as reference points, you can either rely on your memory of the scene, or you can identify an object or surface in your scene and tell your photo editing software to use that as the white point for the rest of the image.
When you do this, your software will change the colour temperature of the photograph so that the object you've chosen is rendered a neutral white or grey. The colour temperature of the rest of the image is changed by the same amount, which should bring everything into line and present you with an accurate, fully colour-corrected image.
How to fix white balance in JPEG images with Photoshop Elelements
1. Choose a shot
This snowy scene in north London has been captured well, at considerable risk to the photographer's frostbitten fingertips. However, the huge expanse of snow and overcast sky have conspired to produce an image that's far too cool.
The white point has been set too low, and so the snow has turned blue. Help is at hand though, and Photoshop Elements offers several ways to correct white balance.
2. Try the Colour Picker
The simplest approach is to use Photoshop Elements' Colour Picker, which lets you tell the software which point to use as a neutral reference.
Click 'Enhance' in the menu bar, then click 'Adjust colour' and select 'Remove colour cast'. The cursor changes to a pipette. As long as you leave the preview checkbox ticked, your image will change when you click, letting you make sure you've got things right.
3. Save your changes
This image is easy to correct. The snow should be white, so when we click on it, the rest of the image jumps into line. You can click several times if you're not happy with the result.
Once you're done, click 'OK' and your changes will be applied. If you're still not happy, click 'Quick' in the list of edit modes on the right hand side, then click 'Balance'. The temperature and tint sliders let you make further changes.
How to fix white balance with Adobe Camera RAW
Correct colours in uncompressed images
1. Download ACR
Go to www.adobe.com and choose the 'Downloads' link. On the right you'll find a link to Adobe Camera RAW. Choose the version for Photoshop Elements, then follow the instructions to download and install it.
Once it's done, open any RAW file from Photoshop Elements and you'll see a dialog box that lets you make non-destructive changes to your file before opening it in Elements.
2. Learn the ropes
You can do a huge amount of editing with ACR, and it's worth spending some time with the software to get used to it. For now, we'll restrict ourselves to adjusting white balance.
Since it's commonly used, the white balance tool is the first option in the right hand menu bar. The options available depend on your camera, but in this case there's the option to choose the lighting in which the shot was taken.
3. Adjust white balance
In this case we'll select 'Daylight', which gives us much more realistic colours without the unwanted blue tint. As with Photoshop Elements, you have the option of using the various sliders to create your own custom white balance and tint.
The software isn't going to get the setting right 100 per cent of the time, so be prepared to get stuck in yourself to ensure it looks right.