What is the fundamental difference between a densitometer and a spectrophotometer?
Densitometers are used more for photography – they determine the “density” or saturation (“darkness”) of a color, say the difference in the amount of a pigment between “pink” and “red”. This can be used both with film and with prints (solid objects). There’s also a bone densitometer that determine the thickness of bone using an X-ray to detect early signs of osteoporosis. Spectrophotometers can look at individual wavelengths of light or the entire spectrum, but it measures how much light (light intensity) is able to pass through the medium being tested. These can also test into the infrared and ultraviolet ranges. These are generally used more for scientific analysis (chemistry, physics, medicine). So other than having somewhat different fields in which they’re used, one is more a measurement of pigment while the other is a relative measurement of light.
