white balance

Why don’t the colours of your knits always look “true” to themselves when photographed? Here’s a post by Tom for our Allover club, to explain why, and help you to address the problem.

white balance: what it is, how to get it, when to use it

One of the most common things I hear knitters say when they come to share photographs of their latest projects is that the “colours aren’t right in the photo, they look different in real life”. The reasons why colours can look different in photographs than to our eye are varied and complex – from the conditions and equipment used to take the photograph, through the processing of the image, to the final way in which we view the image. But perhaps the most important factor in how a colour looks to us in photography is the quality of the light – what photographers refer to as light’s temperature. So, today I’d like to talk about some of the reasons why colours look different in real life, and how understanding the temperature of light and white balance can help us get us more representative colour reproduction – or a more creative use of colour- in our photography. 

To understand differences in the colour of light and the idea of white balance, our story begins with German theoretical physicist, Max Planck. Planck’s studies revealed that as the temperature of a body increases, it begins to emit light.

Max Planck

At about 1500 Kelvin (K), the human eye sees red coloured light emitted, at 5000 K see white light, and as the temperature rises to 15,000 K blue light is emitted. Planck’s findings were central to the publication of the International Commission on Illumination’s 1931 Color Space Model — a way to illustrate all the colours visible to the human eye and to plot the colour temperature and chromaticity of a given light.

CIE colour model showing Planck’s temperature scale (TcK) of light)

This all looks rather technical, but put simply, thanks to Planck’s research, all light sources can be now be assigned a temperature rating based on the colour of the light they emit. For example candlelight is around 1800K, an incandescent light bulb is around 2700K and a fluorescent lamp around 4500K. A white flower viewed under these 3 different lights would look different – in shades ranging from orange to blue.

The same flowers under different lighting conditions look yellow, blue or white

Our eyes, or rather our brains, are very good at interpreting this kind of information in real life- the colour of the flower may look different when viewed in different kinds of light but we still see it as being white. A camera, however, does not process light and colour information in the same way as human eyes and brains.

From the beginning of colour photography, whether using film or digital, the assumption is that you are shooting in direct sunlight at noon on a cloudless day – that is, in light with a temperature of 5500K. But the majority of photography does not occur under these precise conditions. Thus when we take a photo of a flower positioned under light sources which possess a different temperature to the daylight default, the colours just look “wrong” to us:  everything appears too yellow, or too blue! So how do we deal with the apparently unnatural colour cast created by light sources of different temperatures? Well, that’s where adjusting the white balance comes in.

Here’s one citrus slice, photographed under three different lights. Is it an orange, a lime, or a lemon?
Balancing light: warming up and cooling down

White balance is basically the process of adjusting the colour of an image by changing the temperature of its light. With photographic (and cinematic) film, this was first achieved by using an appropriately coloured filter that sat in front of the lens. Digital cameras have freed us from the need for filters: rather than altering the temperature of the light entering the lens with a filter, we can adjust the colour information of the image itself, increasing its light temperature along a scale of blues, or cooling it down with yellows. But hang on a moment? Blue is hot and yellow cold? That’s right: where Plank’s light temperature scale is concerned, blue really is the warmest colour. (I’m casting my mind back here to Kate’s fugitive colour essay, where she explains that our associations of blue with coldness are fairly recent, in historical terms). 

Using incandescent light to illuminate these citrus fruits leads to a orangey-yellow colour cast – the lemon, lime and orange appear very similar in colour (top panel). When we adjust the white balance, the natural colours are revealed (bottom panel)

So how do you adjust colour temperature to achieve a colour-correct white balance? Here are a few quick tips:

  1. Shoot in midday sun on a cloudless day – it’s most likely this is what your camera assumes you are doing anyway… but this is not a very practical solution for most of us (especially not those of us in Scotland).
  2. Use auto-white balance (AWB) – Most cameras and phones will have an AWB setting – (probably located in the advanced/pro settings). Here the camera will use an algorithm to adjust the balance based on the colours it automatically detects in the image. Results can be very variable, especially in unusual lighting, but it’s a good place to start.
  3. Use a pre-determined setting – Again, most cameras will let you change to a pre-determined white balance setting (e.g. Sunny, Cloudy, Tungsten etc.). These settings will certainly get you closer to a more natural look for your colours, but even with a single light source the pre-determined setting could be quite inaccurate – a cloudy day could be anywhere between 6500K and 8000K.
  4. Use a reference and a custom setting – A reference is something you can use to calibrate your image. The reference can be part of your scene (e.g. a wall you know is white) or a portable reference card (these are usually 18% grey – and are the reason why my dear late friend and photographic mentor, Jim Bamford, always maintained that it is “grey, not white, balance”). In both settings the process is the same. Take an image of your reference card, lit in the same way as your subject. Then use this as the reference image for your custom white balance setting. Colours will be adjusted to accommodate the fact that you have stipulated this is grey. This can be done in camera or using post-production software (the process varies depending on make/model but will generally be found in the advanced settings). Keep in mind though, that light temperature in a given scene, especially outdoors, can be continually changing.
  5. Use a colour card and studio lighting – A colour card is simply a more advanced reference. They come with additional software, which is used to extensively calibrate the colour profile of your image. When combined with a light source with consistent, reproducible temperature of light (e.g. studio lighting), this gives the most comprehensive and accurate representation of colour.
My white balance reference hard at work in the studio
Being Unbalanced

Now we have some ideas about how to achieve a “correct” white balance, the real question is, do we actually want it? The quality and nature of light which illuminates a subject is one of the most interesting, creative and rewarding aspects of photography. So why should we try to normalise everything to appear as if it were lit by the midday sun? Certainly, there are times when accurate colour portrayal is crucial – for example in commercial product photography. But most of us are not taking photographs of products for commercial purposes, and the differing (and always beautiful) colour of light is something that allows us to be creative, expressive and playful in our photography.   

Would you guess from these four images that this jar is actually pale grey?

There is a reason why photographers venture out at the crack of dawn, or hang around till sundown, to take advantage of golden hour . . . 

 . . . or stay up all night for a clear moonlit sky.

Though we often talk about “natural” light, this really isn’t something you could define with Planck’s fixed temperatures – a golden sunset could be 2500K, a dramatic overcast sky could be 8000K or a shimmering moonlit sky 4000K. The light of nature is variable, unpredictable and unbalanced. And of course we want to see these scenes, these colours as they appear to our eyes – as golden or blue – because unbalanced colour can be very beautiful.

So how should you display your knits? I think the word should is a problem in that last sentence, and that there’s probably no one answer to that question. But it’s definitely always good to be aware of the default white balance settings of whatever device you have to hand, as well as the effects of light temperature generally on photographic images. It’s also useful to think about how the colours of things, and the colour of light, relate to one another; to adjust your phone and camera settings as and when that’s necessary to achieve a look that feels right to you . . . and perhaps to occasionally embrace some creative unbalance!

Why not find some light and experiment with photographing your colourful knits today?