Modern research telescopes do not use film! They use computers with light detectors that are only sensitive to the number of photons that strike, just like our b&w eye cells that respond to intensity and not color. Modern cameras on telescopes don't care about the wavelength or color coming from the object, but only on the number of photons. Then the computer translates the intensity of light into shades of gray. On top is a visible-light image of the inner region of the Crab nebula taken by HST and displayed in shades of gray. However, the astronomer might prefer to look at a FALSE COLOR image, or a negative image instead of black & white. Sometimes color can be used to bring out faint features.

To obtain information about color, astronomers take separate images using various filters. For all our technological advances, we use essentially the same method that James Clerk Maxwell used in 1854 when he produced the first color photograph.