The colour of light is covered in my Technical Foundations course, and it’s something you need to understand from fairly early on, but let’s recap it here, since it’s one of the 4 characteristics of light.
The rule is – all light has a colour. This colour (with a couple of very rare exceptions which we’re not going to worry about) fits onto the Kelvin Scale of colour temperature. Lower numbers on the scale (1000K – 3000K or so) are very warm, with a yellow/orange tone, and very high numbers (7000K -10 000K) are very cool and blue. Each light source will be only one colour, and your camera can only be set to one colour temperature (called white balance in camera) at a time.
So this is no problem if you are shooting in daylight, and your camera is set to daylight white balance. Everything will look normal. Likewise, if you’re shooting indoors in tungsten light, and you set your camera to tungsten white balance, everything will look normal. The problem occurs either if you’re set to the wrong white balance, or if you’re shooting with mixed light sources.
This is important because you want to render colours accurately. There’s a time and a place for being wildly creative and having odd colours all over your images, but you’re generally better placed to get things right in the first instance, and then play around afterwards. It certainly matters if you’ve been paid to shoot anything – a client won’t be too happy if their perfectly white building comes out bright blue!
Getting accurate colour
The best way to get accurate colour in your images, is to shoot an image with a grey card in, or a white balance card of some type. These give you a neutral tone as a reference point. The grey, black, or white in these devices should be “perfect”, with no colour cast in it at all. They’re so useful because our eyes aren’t great at judging colour accurately. We tend to normalise colour casts, particularly when they’re subtle. This can be a problem in photographs, as of course “white” won’t come out “white”, and things like skin tones will start to look odd too.
Using a grey card or white balance card is really easy. Simply place one in your shot, take an image, and then either set your camera to this white balance (exactly how you do this will vary from camera to camera, check your manual), or adjust the image afterwards in whatever software you use. As long as your lighting remains consistent, you’ve now got a neutral, accurate colour tone that you can work to. You don’t of course need these in every shot, just remember to shoot another image with them in if and when you chance the lighting conditions.
To keep my colours consistent, I tend to avoid using auto white balance as a camera setting. Whilst this can usually do a perfectly decent job, it can vary quite a lot from frame to frame, and this can get frustrating. The reason for this is that auto white balance functions in much the same way as automatic exposure. The camera looks at everything in the frame, balances everything up, and chooses a white balance that fits it best. If the subjects in the frame change, but the lighting doesn’t, there’s a decent chance the white balance will change, as the camera will be fooled by the appearance of different coloured parts of the frame. The way I choose to work is to select whichever white balance is closest to the light I’m working in, and then shoot a reference frame with a white balance card for each lighting condition I’m under