How Colour Photography Works… and, yes, it’s as clear as black and white.

Remember back in junior school art where you learned the primary colours are red, blue and yellow? Yeah, well, scrap that, rewind and prepare to have your mind well and truly blown.

For where light is concerned, the three primary colours are red, blue and… drumroll, please… GREEN, with secondary colours of yellow, magenta and cyan. And, combined, these three primaries create white light.


Everything digital – photography, TV, film – works on the R/G/B basis. And we have Scottish physicist, James Clerk Maxwell (aided and abetted by photography innovator, Thomas Sutton) to thank for this. It was Maxell who hit on the fact that every colour that exists can be successfully reproduced through the correct proportional mix of the RGB primary colours… and that this knowledge could be applied to photography to create colour prints. Under Maxwell’s direction, Sutton took three individual monochrome photographs – each with a different coloured filter – of a piece of tartan ribbon. Combined, the three resulting images created the image and, with it, the three-colour process that has been the bedrock of colour photography, ever since.

And if you thought that was batshit crazy, well, hold onto your hat. Because we don’t actually “see” in colour; what we do is “perceive” in colour. Putting it really simply (because, frankly, this is as much science as I can take in in an afternoon, so I need to dumb things down so I can keep up) photoreceptor cones in our eyes pick up on the relative brightness of wavelengths of light and send that info’ on to our brain to process.  There are three types of photoreceptor cones that do this and, yep, you guessed it, they are each most sensitive to one type of light wavelength: red, green or blue. And, just like Thomas Sutton’s combined processing, the brain gets hold of all this info’, whacks it together and goes, “Thanks very much, that’s gonna be mustard, teal and cerise… Say what? Mustard, teal and cerise? Girl, I don’t care if it’s Orla Kiely; £50 for this car-crash of a cushion cover? Are you for real?” or something to that effect. And that’s when you know it is time to leave the home furnishing section of TK Maxx.

Without those photoreceptor cones, we’d see everything in varying shades of black and white (and successful interior-design would be so much simpler). And that’s exactly how a camera collects information. It doesn’t record colour, it simply records the levels of blue, green and red light reaching the sensor; so three variations of a black and white image.


It is the camera itself that transforms the image into colour, and it does this by using a colour filter array (CFA) or colour filter mosaic (CFM). Like our eyes’ photoreceptor cones, a camera’s CFA/CFM is made up of red, green and blue receptors: a mosaic of tiny colour filters placed over the pixel sensors of the image sensor, that capture the colour information and, ultimately, transform it into the infinite array of colours that we see in modern photography today.

The most common RGB filter: the Bayer Filter.

The most common RGB filter, the Bayer filter, has a ratio of 50% green to 25% red and 25% blue photosensors – designed to mimic the physiology of the human eye which is more susceptible to green light. These sensors are now better known as pixels. Each pixel is only able to record one of the three primary colours; so there is still information missing at this point. This is where algorithyms come into play to invent and add this missing information to the final raw image  – either in-camera (resulting in a Jpeg or Tiff file) or externally, using an editing platform such as Camera Raw. (Hence the fact you have a sharpening tool on camera raw.)

But regardless of whether or not you have a bit of editing to do, it’s still pretty incredible that the whole spectrum of colour that we perceive/see comes from these three primary colours. And if the secondary colour names sound familiar, that’s because they’re the colours your printer uses. Indeed, if you were to look very, very closely at, say, red print – magnifying-glass-closely – you would see that it was a mixture of yellow and magenta pixels; ditto yellow + cyan = blue, and cyan + magenta = green.

PRIMARY COMBINATIONS                                                   COMPLIMENTARY COLOURS

RED + GREEN         = YELLOW                                                   GREEN + MAGENTA  = WHITE

BLUE + GREEN             = CYAN                                                    BLUE + YELLOW       = WHITE

BLUE + RED          = MAGENTA                                                  RED + CYAN                = WHITE

It’s these combinations that we use in white balance adjustment. If a photo needs to look colder, we reduce yellow to boost blue. If a photo needs to look warmer, we reduce blue to boost yellow. If shooting in raw, this can be done in the edit, so there isn’t much point faffing about with it on the shoot. It can all be sorted once the shot is in the bag.

At edit stage, Hue refers to actual colour depth – and this too can be altered.

Colour contrast – the use of complementary colours to attract the eye – is a well-known advertising and photographic trick.
258sThe IKEA and Lidl logos are prime examples.This is because the human eye has to readjust to view yellow, which makes it more prominent a colour than any other we view. Yellow is THE most powerful colour – that’s why it’s used for warning signs. No doubt, that’s why nature uses it similarly (think wasps for starters).  Complimentary colours pop out – my Red Barn photo is a case in point and it is the yellow of the rapeseed field that is most dominant. This probably also explains why so many photos of daffodils make it onto Instagram.

The use of certain colours next to each other create colour harmonies; something worth remembering when composing shots; contemplating props or in the final edit – but whether you go high or low, it’s all down to personal preference and purpose. Tom Hunter’s use of “cold” colour, for example, helps to portray detachability, conflict, isolation and works to remove the viewer and push them back from the image.

It’s fair to say, this colour-shebang has left me with quite a lot to think about. But I will leave you with one question that I’m still pondering…

If we only perceive colour, we don’t actually see it and it is all the work of our miraculous, extraordinary brain, does it even really exist?

Are we actually living in a black and white world?


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