Why is colour appearance device-dependent?

Colour on screens

When we look into our surroundings or into nature, we can see a myriad of colours. The way we perceive colour is complex: the basic principle is that light enters our eyes, and the information carried by light is decoded by our eyes and brain to give us the perception of a specific colour. (However, even that statement is too simple, as the environmental context also plays a critical role in colour perception, as well as our experiences and memories.)

When we try to capture colours that we see in our world using a camera, phone or tablet, the way that the camera processes the light that enters it is different from the way that our human eyes and brain process light. As well, each type of device and each manufacturer process the light differently from each other. When we then display a digital image captured by a camera, the device displaying the image will try to match the way we perceive the colour of the real-world object, but the match will not be exact. So when we compare the colours we see in the real world with the colours we see displayed on a device (like a phone, tablet, laptop, TV), they may be very close in appearance, but not an exact match. There are even variations from one type of device to another (e.g. a phone vs. a computer screen) and within specific devices themselves (e.g. different brands or models of phones).

Printed colours

Many people have experienced the disappointment of a vivid digital design coming out of the printer appearing darker and more muted. Why does a print of an image look different from the same image displayed on a screen?

Colours on a display are self-luminous: they are made up of tiny light-emitting pixels. Red, green, and blue pixels can combine their emitted light to form very vivid colours. These vivid colours can appear brighter than the corresponding colours printed on a page, which are only reflecting light, not emitting their own light.

Furthermore, while cyan, magenta, and yellow-coloured inks each reflect light from different portions of the spectrum, this means they absorb the rest. So, when those inks are layered on top of each other to mix new coloured areas, their light-absorbing abilities are combined. Since more light is absorbed, what we perceive as the mixed colours tends to appear darker.

Computers try to manage these differences between the appearance of a screen and the appearance of a printed page, often by shifting the appearance of colours on the printed page. For example, the appearance of greens, blues and purples become lighter. To lighten a printed colour, more of the underlying white paper shows through between the dots of ink, and the colour therefore appears less vivid than its digital version.

Find out more:

The way various devices process the light they receive and display images is extraordinarily complex. Professor Steve Westland, at the University of Leeds, discusses Colour Management and Fidelity of Digital Systems in a lecture for undergraduates (some background required).