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White Balance
You will often see definitions of white balance such as "making sure that things that are white appear white in your photograph". This is a rather over simple view as if the white balance is set wrongly, it affects every colour in your picture.
It would probably be better to have called it 'colour balance' however white balance has stuck since the calibration of this setting (either in camera or in post processing) usually involves a white piece of paper or identifying an object that is white in the scene, and then the camera can apply the appropriate correction and all colours should then appear correct.
For photographers switching over from film to digital, the white balance setting on the camera will be something new, although if you shot slide (transparency) film, the concept should be familiar. When you chose which film you wanted to use, you could pick between 'daylight balanced' film or 'tungsten balanced' film. This referred to the white balance of the film.
So What Is It?
All objects in your picture will have a particular colour - however how they are seen by the human eye as well as the camera will depend on the properties of the light illuminating them. The human eye/brain is very good at compensating for these differences so that you don't really notice huge colour shifts when you move from inside the house (lit with an incandescent/tungsten bulb) and outside into the daylight. You brain is processing the signal from your eye and create something that looks natural.
The image data from the sensor in your camera also needs to be processed to get the colour balance correct. If you are shooting JPEG files, then this will be done by the camera and the colour correction will be applied before the JPEG file is created. If you shoot in RAW format, the camera only stores what it thinks the correction should be - it does not actually apply it. When you process the RAW files on your PC, you can choose to use this setting, or select you own.
Lets consider an example. In the evening, the light is usually more orange than around midday. The camera must compensate for this by adjusting the bias on the seperate red, green and blue channels to give a more balanced colour. In the evening light the camera will correct the image by increasing the amount of the blue channel and reducing the red (since the natural light already has plenty of red). In the midday light, it is the blue channel that will be boosted.
<pictures to illustrate>
The white balance within the camera (or in the RAW processing sioftware) is usually controlled by 2 different settings:
- colour temperature (measured in Kelvin)
- tint
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Colour Temperature
The colour temperature of a light source is determined by comparing its chromaticity (it's quality of colour without taking account of the brightness) with that of an ideal black body radiator (an object that absorbs all light that falls on it). When a black body radiator is heated up to high temperatures, it starts to give off light - the colour of which is dependent on the temperature.
Temperature in Kelvin = Temperature in Celcius (Centigrade) + 273
The temperature at which the heated black body matches the colour of the light source is called the colour temperature of that light source. At temperatures of 1000-3000K the body glows red - but as the temperature increases, the becomes white, and then at very high temperatures it glows blue.
A major source of confusion is that lower colour temperatures are red, higher temperatures are blue. However photographers still often talk about warm light as having a red cast and cooler shades being more blue. So when someone talks about the warm light, make sure you know which they mean. |
Some Approximate Values
| Source |
Approximate Temperature |
| Candle Flame |
1850K |
| Incandescent (Tungsten) Light Bulb |
2600 - 3300K |
| Studio lighting |
3400K |
| Daylight - at sunrise |
2000 - 2500K |
| Daylight - early morning / later afternoon |
3500K |
| Daylight - mid-day |
5500K |
| Overcast sky |
6000 - 7000K |
| Electronic Flash |
5500 - 5800K |
| In the shade |
7000 - 9000K |
Getting the White Balance Right
Getting this right is one of the most important factors in getting high quality digital images from your camera. There are four options available to you:
- Use the cameras 'Auto White Balance' setting (icon is usually 'AWB').
- Use a preset white balance setting.
- Set the colour temperature manually (if supported).
- Use the custom white balance calibration facility on your camera (if supported).
- Shoot in RAW format and select your white balance on the computer in post processing (if supported).
The last of these can be used in conjunction with the first three, so we'll look at this first.
Shoot in RAW
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There are many advantages to shooting in RAW format rather than in JPEG (assuming your camera has a RAW mode), but probably the most compelling reason is that the camera does not apply any colour correction to the image data - you do this when you process the RAW images on your PC.
The white balance setting on your camera are stored in the RAW file as metadata (information only) so that when you bring up the file on your PC, you can see what white balance correction the camera would have applied had you been shooting in JPEG. However you are free to change this, or have your RAW processing software analyse the image and suggest it's own white balance colour temerature.
Something that most DSLR photographers have done at one time is to change the white balance setting for a particular photo, and then forget to change it back. You can end up with a whole string of images with either a red or blue cast on them which can be very hard to fix if you use JPEG. Shoot in RAW however, and you can just move the colour temperature slider in your software and voila! (how's my French?)
Image right shows the basic parameters in Adobe Camera Raw. |
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Auto White Balance
This is the mode that most photographers tend to use, and even if you don't, it's always a good one to return it to after shooting just in case you need to grab the camera in a hurry. If shooting in RAW mode, you can just leave it in this mode most of the time.
How Does Auto White Balance Work?
Every camera is most likely going to have its own set of algorithms to work it out from the image data. There is a lot of debate on this on the internet, so we are not going to add to it here. There are some sites that talk about the cameras white balance sensor. Most cameras do not have a dedicated white balance sensor, but derive the settings from the image data from the main sensor after the picture is taken.
The best thing to do is just accept the most of the time, the AWB setting gets reasonably close, but occasionally it can be fooled (another reason to use RAW mode!).
Preset White Balance Settings
Personally I don't use these very often, although there are two circumstances when they are useful.
- Under lighting conditions at the extreme end of the temperature scale, the auto white balance often plays it a little safe (e.g. in low power tungsten light when the colour temperature might be around 2650K, the camera will select 3300K). Likewise with heavy shade where the actual colour temperature can be as high as 9000K.
- Panoramic pictures. If you plan on stitching together multiple shots to create a single picture, you must select a preset white balance otherwise you will find that the colour balance changes from one picture to the next and the end result won't look convincing.
Setting the Colour Temperature Manually
If you have a dedicated meter for this, then this may be something you will want to try - but for most people, one of the other options is generally more suitable. The only time we can think when this might be useful is if you are shooting at the extreme ends of the colour temperature scale and the preset values seem a little conservative. For example, some Canon DSLR cameras use a setting of around 7000K for shade. It can be much higher than this under heavy shade conditions.
In general, we would advise use the custom white balance function, and shoot in RAW.
Custom White Balance
This may work in slightly different ways depending on your camera, however the basic idea is that you take a photograph of a piece of white paper or a grey card, and you tell the camera to calculate the correct white balance settings based on this image. By doing this, you are tuning the camera to the exact lighting conditions present.
Although neither of the authors use this very often (as we both shoot in RAW mode), it can be useful for photographers that use JPEG or are shooting in slightly unusual lighting conditions.
White Balance Bracketing
Some cameras may give you the option of bracketing your shot. This means it will take three pictures instead of one - with the second and third pictures using a white balance setting either side of the first shot. This may be something you will want to use if shooting in JPEG mode but is not needed if you use RAW.
One Last Point
Don't rely too much on the cameras LCD screen when checking to see if the white balance looks good. The quality of the colour rendition on these screens is variable.
Actually one more last point ...
If you like using filters (the glass ones that go in front of the lens, not the big list of effects in Photoshop) you may think it's a good idea to use one of the 81-series filters for warming up an image. These were traditionally used to correct for different lighting conditions on film cameras where the white balance was fixed, but on a digital camera you can do this in the menu, so these filters become pretty pointless.
If you must use them though - remember to turn OFF the Auto White Balance and set it to the Daylight preset. If you don't, the filter will warm the image, and the auto white balance will 'correct' it back the what it thinks is neutral.
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