When spacecraft visit other planets, why can they take colour photos?
In order to send pictures back, they are typically digital images transmitted by radio waves. It is my understanding that digital black&white cameras consume less power, are simpler, more reliable, and higher resolution than digital colour cameras. Instead of having two visible-light cameras on a mission, they send one good b&w and a series of filters that can be used to take three filtered pictures and assemble the three component colours back here on earth to create the true-colour image. So, in a very real sense, they do take “colour photos,” they just do it one colour at a time. A little more background: a colour CCD (a CCD is a “charge-coupled device” which is capable of measuring and reporting the amount of light that hits it) for a digital camera has three different kinds of photoreceptors for each picture element (pixel) – they could be red, green and blue, but I think they typically use one for luminance and two for colour differencing. With a B&W sensor they have only one kin
