Regular cameras used on Earth make pictures by letting light chemically change film. This is important because digital information can be downlinked to Earth in radio waves, whereas regular camera film cannot. In addition to cameras, which record light, there are other ways to make images that record different kinds of electromagnetic radiation. The best example of this on Earth is the special film that can capture heat or infrared rays. DS1 and other spacecraft do different kinds of radiation imaging using a variety of tools.
Photometers are optical instruments that measure the intensity or brightness of light from a source.
Spectrometers are optical instruments which split the light received from objects into their different wavelengths, each one being a different color. For example orange light may contain red, yellow orange and pink light all mixed together. Spectrometers let you see this. Observing a bright white light shining on its surface makes it look like rainbows. An infrared radiometer is a telescope-based instrument that measures how much heat is coming from a target.