The digital camera, colour perception and
A work in
The digital age has brought us ever cheaper and more wonderful cameras. Now just about everyone can
own an advanced digital camera with more features than we know what to do with.
At the same time we now have new methods of lighting: A range of compact fluorescent lamps (CFLs), which have
much lower heat dissipation than incandescent lamps, light-emitting diodes (LEDs) of various kinds, and
probably more to come.
However, these newer lamps do not produce a continuous spectrum of light, such as we get from the sun or from
incandescent lamps. Instead, they produce light at very sharply defined wavelengths, and it is only by
judiciously combining the various wavelengths available that we get light which approximates our "normal" daylight
or white light. We can trick the human eye into thinking that the spectrum is continuous, but as we will see
that is not true and there are some interesting consequences.
At the same time, the modern digital camera also performs some interesting tricks in order to capture colour.
The most common scheme is to detect the colours in a scene by means of three sets of sensors, corresponding to
three primary colours: red, green and blue. If we then reproduce the scene using these three colours, again
we trick the human eye into perceiving colour... but we are not actually seeing the original colours in the
scene. Sounds complicated?
Let's look at the whole sequence, where we use a new artificial light to illuminate a scene, capture the scene
with a digital camera, and then display it on a pc screen:
||Reflects all wavelengths of light
|Illuminate with CFL lamp
||Reflects only certain specific wavelengths
|Observe with human eye
Eye/brain trick #1
|Capture with digital camera
||Capture specific wavelengths into 3 categories: red, green, blue
|Display image on CRT / flat screen
||Display in RGB - Eye/brain trick #2
These pages are an exploration of the above themes. It will be interesting, and may even provide some
Next: The visible spectrum