Do you want your whites their whitest? Use Tidy Det…. no, wait, wrong commercial. Do you want your whites their whitest? Use White Balance. That’s better. OK, I’ll stop with the bad humour now.
In this instalment of the ongoing Photo Basics series, we’re going to look at a camera control that can be confusing but really shouldn’t be: White Balance. In very simple terms, white balance is used to keep white things white. Or grey things grey. And all other colours their ‘proper’ colour too. Note that I’ve highlighted the word ‘proper’. We’ll come back to that later in the article. Essentially white balance is used to maintain a ‘neutral’ colour balance. Light has many different characteristics. A future article on light will discuss in more detail. But for now, what you need to know is that light has colour. It can be warm yellow/orange. It can be cool blue. It can be many different colours. But one thing that’s rare to find is true white light. We think of a lot of different types of light as white light. But in reality, there is very little true, white light in the environments we work in. This colour of light has an impact on photography. How?
Your eyes do a pretty good job of compensating for different colours of light. You perceive a red apple as red in warm tungsten light and cool fluorescent light. You perceive the leaves of a tree as green in noon daylight, in shadow and in sunset light. This ability of the human visual system to compensate for lighting differences and perceive colours as the same is called colour constancy. This constancy of colour isn’t absolute and it can break down in extreme lighting conditions. But in large part it holds true. Digital camera sensors (and film) don’t exhibit colour constancy. Quite the opposite, in fact. Colours will take on very different hues in a photo depending on the colour of the light source. You need to tell the camera what the light source is so that colours appear ‘proper’. There’s that word again. With film cameras this is done through the use of film that was made for different lighting conditions (e.g., daylight, tungsten, fluorescent) or through the use of filters on the lens that alter the colour of the ambient light hitting the film to create the proper colour balance. With digital cameras this is done with the white balance function.
Using the white balance function of your camera, you tell the camera what lighting conditions you’re shooting in. With this information, the computer in the camera then knows what colours ‘should’ look like under that lighting condition and makes any necessary compensations to bring you back to a ‘neutral’ colour balance.
What is ‘neutral’? In the simplest sense neutral means no bias to one colour or another. It means that if you’re measuring a white target it measures as R=B=G at 255, 255, 255. If you’re measuring a middle grey target it measures as R=B=G at 118, 118, 118. What it means is there is no colour cast or colour bias in the image. In this sense the colours in your image are ‘proper’ or correct.
Most cameras have several white balance ‘presets’. These presets are programmed to certain types of lighting conditions and the ‘average’ colour of light under those conditions. A Daylight white balance preset is typically programmed to a setting of around 5000K which is the colour of light under daylight with a clear sky (no clouds) and the sun high in the sky (i.e., not early morning or late afternoon). A Cloudy preset is programmed to about a colour temperature of 7000K which is a much cooler, bluer light. A Sunset white balance preset will be programmed to a colour temperature of around 3500K. This is a much warmer, yellow/red/orange colour of light. Other presets such as Tungsten, Fluorescent, Shade and the like are similarly programmed to the typical colour of the light in those settings. Most advanced cameras also have a Custom setting which allows you to calibrate the camera to the specific colour of light you are working in. Check your camera manual for how to set a custom white balance. Typically it involves taking a photo of a white or neutral object in the light you’ll be working in. The camera then reads the colour of that object and makes any necessary corrections to get the object back to white or neutral.
Most cameras also have an Auto white balance setting. In this setting the camera reads the conditions you’re shooting in and makes assumptions about the colour of the light. It then makes adjustments to the colour balance to try and bring things back to neutral. Auto white balance can work well but it can also get fooled. In general, Auto white balance will work reasonably well in daylight conditions. When the colour of light becomes heavily skewed in one direction or the other such as under tungsten or fluorescent light, the auto setting typically doesn’t work as well and will leave a colour cast in the image. Auto white balance may also fall down if there is an abundance of a single colour in the image that will skew the light reflected by the subject. Auto white balance will also fall down in mixed lighting conditions. A classic example of this is a room with warm tungsten light in the light fixtures and cooler daylight coming in the windows. You’ll end up with a colour cast in one direction or the other and sometimes both. In the images below, the first was shot with an Auto white balance setting. The lighting was mixed with tungsten bulbs in the bedside fixtures and daylight coming through a large window to the camera left. In the Auto setting, the camera took the white balance of the larger light source and the tungsten lights impart a very warm colour cast. In the Tungsten setting, the light from the bedside tables is now neutral but the rest of the shot is very cool due to the difference in light colour temperatures. These types of mixed lighting conditions can be very difficult to deal with.
In the next example, the image of the tree bark was shot under somewhat cloudy skies. But it wasn’t a really deep cloud cover that would result in a very blue light. Using the Auto white balance setting, the bark came out pretty much as it should. Generally grey with some hints of yellow/brown and green. Using the Daylight preset; however, renders an image that is far too warm/yellow. These are otherwise untouched RAW files, just as the shots of the hotel room above are.
Auto WB will also often cancel out a desirable colour cast. Shooting, for example, in sunrise/sunset conditions we have the beautiful ‘golden hour’ light. It’s warm light and there are lots of reds, yellows, oranges. Using the Auto setting will generally negate much of that desirable colour. But using a Daylight setting will give us back that warm glow and rich colour palette.
Can you use white balance creatively? Sure you can! There’s nothing in the ‘rulebook’ that says there’s only one possible white balance setting and it’s the one that exactly corresponds to the light you’re shooting in. You can be very creative and adjust the white balance to give any number of variations to the colour balance in an image. Going back to the image of the bark, what I was most interested in was the texture. The colour was less interesting because it was basically just grey. But all that texture and shadow/highlight contrast had lots of appeal. As I was looking at that shot back in my office after the fact I wondered what I might get if I played with the white balance a bit. Warmer? Nope, I knew what that looked like and it wasn’t anything appealing? Cooler? Oh! Wait a second. These really interesting blues started to come out and the greens that I knew were there really began to become vivid. With a little more adjusting, some judicious cloning/healing of unwanted detritus and sharpening, I ended up with the version below. Realistic? No. But interesting to me. You may not like it and that’s fine. But it shows how we can get creative with the white balance setting and how white balance can be used creatively to set an entirely different mood for an image.
There is a caveat. Of course there’s a caveat. There always is, right? The caveat is that to have this level of flexibility you have to shoot RAW. Since raw images are not a fixed file format the white balance setting is only a tag in the image metadata. It’s not hard coded. If you shoot JPEG the white balance is locked in and changing it in editing will most often lead to some very unpleasant results. Trying to adjust the white balance to a cooler setting on a JPEG of this bark image illustrates this. Lost are the verdant greens, reds and other interesting colours that are in the image. The entire photo has just taken on an unpleasant blue colour cast.
What this example should also illustrate is that if you are going to shoot JPEG, you really need to nail the white balance in the camera otherwise it’s going to be very difficult to fix after the fact.
That concludes this article in the Photo Basics series. Are you using the white balance settings creatively in your photography? Feedback most welcomed.
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