A colorimeter and a spectrophotometer both measure light, but they do it differently.

A spectrophotometer measures light intensity across many wavelengths, producing spectral data. Because it samples much more of the spectrum, it can distinguish fine differences in wavelength and is useful for tasks like measuring reflected/transmitted light, profiling prints, or analyzing materials.

A colorimeter uses filters to approximate how the human eye responds to color, typically reducing the measurement to standard color values such as XYZ or Lab. It doesn’t capture a full spectrum; it measures through broad filtered channels instead.

In practical photography terms:

• Colorimeters are commonly used for display calibration and can be very effective there, especially when designed to match human visual response.
• Spectrophotometers are more versatile because they can measure prints/paper as well as some displays.

So the main difference is measurement method: filtered human-vision-style channels vs. full spectral sampling. Neither name simply means “cheap vs. expensive,” “display vs. print,” or automatically “more accurate.” The better tool depends on what you need to measure.