Painting with light

Photography is painting with light.  This is the light that we use - the light from the sun, seen here through a spectroscope, a device which splits tha light into its component colours.  Sunlight contains a continuum of colours, the familiar rainbow.  Use the spectroscope to look at other light sources and you can often see large gaps in the spectrum, or one or two particularly strong colours, as those light sources produce a more limited range of colours.

Incidentally, this spectroscope has a rather small eyepiece, and it was quite difficult to get a photograph looking through it.  The eyepiece lens was almost touching my camera lens!