Colour

September 2012

Does colour really exist? It’s an interesting question. Different surfaces absorb and reflect different frequencies of light (as light travels in waveforms) and different frequencies are perceived by us as different colours as we have 3 different receptors (cone cells) in our retinas which respond to 3 different ranges of frequency hitting them; red, green and blue. These receptors fire off different signals to our brain which in turn perceive them as colours and thus it can be argued that colours are actually a function of our brains and not the “real” world as much as it can be argued that color should be spelt without a “U”!
The colour digital camera responds in a similar way to the human eye as different sensors are allocated to respond to varying ranges of light frequency. This is done by employing the use of colour filter arrays or by splitting the light entering the camera into its component RGB with the use of a prism. The corresponding sensors then output the level of light hitting them without any actual colour information. It is actually only it’s designation that tells us what colour it is. The information from all three sensors are then combined to give us an overall colour representation.
Colour film works in a similar way utilising different layers of a photosensitive salt (a chemical sensitive to light) called silver halide. These crystals are dyed so they are not affected by any other colour than which they have been designated to. Different brands and types of film use layers of emulsion with different types of dye so each type of film has its own unique look and feel.

Before colour film was invented the effect of colour was recreated using various cruder methods. One method called Technicolor required 3 different film strips to be used, each corresponding to red, green or blue. That is why older colour movies often look rather fake as if they had been painted. In fact in the very early days of film, the developed film strip itself was hand coloured, frame by frame, a laborious and costly process!