If you've spent any time shopping for color measurement equipment, you've probably run into all five of these words used almost interchangeably — sometimes even by the manufacturers themselves. They are not interchangeable. This guide untangles what each device actually does, where the names came from, and which one belongs on your bench.
The short answer: they all measure electromagnetic radiation
At the most basic, physics-textbook level, a spectrophotometer, a colorimeter, and a densitometer are all instruments that detect and measure electromagnetic radiation — typically light in or around the visible spectrum. A light source illuminates or passes through a sample, a detector captures what comes back, and the instrument turns that signal into a number. Everything else is a matter of how that light is captured and what the resulting numbers are used for.
Important distinction: most of these devices aren't for measuring color at all
Here's where a lot of confusion starts. Search for "spectrophotometer" and you'll find laboratory instruments used for chemical analysis — devices that shine light through a liquid sample and use the absorption pattern to identify or quantify a chemical compound. Search for "colorimeter" and, alongside color-matching tools, you'll find handheld chemistry colorimeters used to test water hardness, chlorine levels, or nutrient concentration.
These lab and field instruments do detect visible (and often UV or near-infrared) light, and many go well beyond the visible range altogether. But they're not measuring color the way we experience it — they're using the light's interaction with a substance to deduce its chemical composition. A UV-Vis spectrophotometer in an analytical lab and a benchtop color spectrophotometer in a paint lab share an ancestor and a name, but they solve entirely different problems.
Ametra specializes in color measurement, so the chemical-analysis branch of this family tree isn't what we'll be discussing here — but it's worth knowing it exists so you don't end up buying the wrong kind of "spectrophotometer" for a print shop or a paint lab.
In the science, art, and industry of color measurement, the same five names — spectrophotometer, colorimeter, spectrocolorimeter, densitometer, spectrodensitometer — show up again, but with definitions and functionality specific to color work. That's the family we're covering below.
Three ways color gets measured
Before comparing instruments, it helps to know that color measurement itself splits into three categories, and not every device handles all three:
- Reflected color — the color of surfaces: paint, fabric, plastic, printed material, packaging. This is the color measurement most people think of first, and it's the largest use case by far.
- Transmitted color — the color (and clarity) of transparent or translucent substances, such as glass, film, or liquids. Instruments built for this often double as haze meters for measuring optical clarity alongside transmitted color.
- Emitted color — the color of light itself, relevant to lighting evaluation and to displays, screens, and other self-illuminated surfaces. This is where lighting conditions and screen-to-screen color consistency become relevant.
Spectrophotometers vs. colorimeters
These are the two workhorse terms in color measurement, and while the industry isn't always formal or standardized about it, the practical distinction is consistent.
What a spectrophotometer does
A spectrophotometer builds an actual spectrogram of the measured visible spectrum. It does this by splitting the light — emitted or reflected off the sample — into its component wavelengths using a prism, a diffraction grating, or a sophisticated system of multiple colored filters. That split spectrum is then projected onto an array of detectors that measure the intensity at each waveband. Modern color-measuring spectrophotometers typically divide the visible spectrum into 35–40 measured wavebands — enough resolution to reconstruct an accurate spectral curve for the sample.
What a colorimeter does
A colorimeter works differently. Rather than resolving the full spectrum, it's built to mimic human color vision directly, typically using three detectors filtered to respond like the red, green, and blue receptors in the human eye. Three data points are enough to calculate standard color coordinates such as L*a*b* — but not enough to reconstruct a full spectrogram. Some colorimeters attempt to extrapolate a spectrum from those three points anyway; the results tend to be noticeably inaccurate compared to genuine spectral data.
Side-by-side comparison
| Spectrophotometer | Colorimeter | |
|---|---|---|
| How it measures | Splits light into 35–40+ wavebands to build a full spectral curve | Three RGB-filtered detectors, mimicking human vision |
| Output | Full spectrogram + color coordinates | Color coordinates only (e.g. L*a*b*) |
| Best for | Paint/ink formulation and matching, metamerism evaluation, quality control that needs traceable spectral data | Quick pass/fail comparisons, matching to standard palettes like Pantone, high-end display and lighting measurement |
| Complexity & cost | More complex construction, generally higher cost | Simpler construction — ranges from very affordable to specialized/premium |
| Stability | More moving parts/optics can mean more susceptibility to interference | Simpler optical path can mean more stable repeat measurements |
These two device types occupy genuinely different niches rather than competing head-to-head. Spectrophotometers are essential wherever someone needs to work backward from a measurement to a formula — paint and ink matching, where pigment and substrate spectra have to be calculated and adjusted, is the clearest example. Spectral data is also what makes it possible to detect and quantify metamerism — the phenomenon where two colors appear to match under one light source but not another. That said, spectrophotometers are more complex, larger, more expensive, and can occasionally be less consistent in certain conditions precisely because there's more optical machinery that can introduce variation.
Colorimeters have a narrower job description — measuring color coordinates and, for emitted-light versions, light intensity — and nothing more. That narrow focus is exactly why you'll find them at two opposite ends of the market: inexpensive, portable tools for quick color comparison and matching against a predetermined standard (a Pantone palette, for instance, or a brand color standard), and, at the other extreme, high-end, high-accuracy instruments prized for the very stable measurements that come with a simpler optical construction — most often seen in professional display and light measurement.
Spectrocolorimeter: a fading but still-used term
"Spectrocolorimeter" is a term that's slowly falling out of use, and its history explains why it's confusing. Decades ago, colorimeters mostly measured emitted light and were built for lighting and display work. A smaller category of devices used an array of multicolored LEDs to also measure reflected color, effectively giving a colorimeter some spectral-style discrimination — and these hybrids were often branded "spectrocolorimeters."
Today, broadband high-CRI white LEDs and far more capable detectors have made that particular multicolored-LED mechanism largely obsolete. Reflected-color-measuring colorimeters are now common and don't need that workaround — yet plenty of current products, including some in Ametra's own colorimeter lineup like the Basic QC Portable Spectrocolorimeter, still carry the "spectrocolorimeter" name out of convention. There's no hard, universally enforced rule here — it's largely a legacy label.
Densitometer and spectrodensitometer: a different lineage, now merged
Two more terms worth knowing, especially if you work in print: densitometer and spectrodensitometer.
A densitometer is, fundamentally, a different kind of device — it measures optical density, i.e., how effectively a material blocks light, rather than color as such. That said, the line blurs quickly: reflection densitometers use a lamp and a light-sensitive detector, the same basic ingredients as a spectrophotometer or colorimeter. And in printing specifically, measuring ink density has for decades been the standard way to evaluate the quality and consistency of color reproduction on press. That made densitometers the de facto "color measurement" instrument of the printing industry for a long time.
As spectrophotometers became smaller, more rugged, and considerably cheaper, they started encroaching directly on densitometer territory — a modern spectrophotometer can calculate the density of reflective materials like inks and paints from its spectral data using well-established conversion math. That convergence is what produced the spectrodensitometer: a spectrophotometer that reports both full color data and density, giving press operators one instrument instead of two. Ametra's own Print Portable Spectrodensitometer is a good example of exactly this combination, purpose-built for print quality control.
Pure optical densitometers are genuinely rare in the printing industry today — most shops have moved to spectrodensitometers or full spectrophotometers. Some industry veterans still call their instrument a "densitometer" purely out of habit, even when it's a fully spectral device. If you're evaluating equipment, it's worth asking directly what data the instrument actually reports rather than relying on what it's called. (For a deeper technical comparison, see X-Rite's breakdown of densitometers vs. spectrophotometers.)
Quick-reference summary
| Device | What it measures | Where you'll find it |
|---|---|---|
| Spectrophotometer | Full spectral curve (35–40+ wavebands) of the visible spectrum; color coordinates are calculated from it | Paint and ink formulation, metamerism evaluation, R&D and QC labs |
| Colorimeter | Color coordinates via three RGB-style detectors | Affordable field/QC color matching, or high-end display and lighting measurement |
| Spectrocolorimeter | Reflected color, via a colorimeter-style device (legacy LED-array term) | Increasingly just called "colorimeter"; term used less often today |
| Densitometer | Optical density (light-blocking ability) of inks and paints | Legacy print QC; mostly obsolete as a standalone device today |
| Spectrodensitometer | Both full spectral color data and optical density | Modern printing and packaging quality control |
So which one do you actually need?
A few rules of thumb, based on what's above:
- If you're formulating or matching paint, ink, dye, or plastic and need to account for how a color shifts under different lighting, you need a spectrophotometer — check out options like the Ametra Lab Benchtop Spectrophotometer or the portable Ametra Industrial D/8.
- If you need a fast, affordable way to check whether a color falls within tolerance of a known standard, a colorimeter like the Ametra Match will usually do the job for less money and complexity.
- If you're measuring liquids, films, or other transparent/translucent materials, look at transmittance-focused instruments such as the Ametra Clear or Ametra Liquid, which also report haze.
- If you work in printing or packaging and need both color and ink density on press, a spectrodensitometer such as the Ametra Print covers both jobs in one device.
Still not sure which category fits your workflow? Browse the full Ametra color measurement lineup, or get in touch — we're happy to help you match the instrument to the job rather than the other way around.
Frequently asked questions
Is a spectrophotometer more accurate than a colorimeter?
For most color-matching and formulation work, yes — because it captures a full spectral curve rather than three broad data points. But "more accurate" depends on the task: a well-built, purpose-specific colorimeter can be extremely stable and repeatable for the narrow job it's designed for, sometimes more so than a spectrophotometer being used outside its ideal conditions.
Can a colorimeter measure metamerism?
Not reliably. Detecting metamerism requires comparing full spectral curves under different illuminants, which is exactly what a spectrophotometer is built to do. A three-point colorimeter simply doesn't capture enough data.
Is a spectrodensitometer the same as a spectrophotometer?
Nearly. A spectrodensitometer is a spectrophotometer that also calculates and reports optical density values (commonly used in print quality control), typically alongside standard color coordinates and spectral data.
Are "spectrocolorimeter" and "colorimeter" the same thing today?
In most current usage, yes — "spectrocolorimeter" is largely a legacy term from when reflected-color measurement with a colorimeter-style device needed extra hardware to work. Modern instruments do it natively, but some manufacturers keep the older name.
Do I need a densitometer if I already have a spectrophotometer?
Almost certainly not. Modern spectrophotometers and spectrodensitometers calculate density from spectral data, which is why standalone densitometers have become rare outside of legacy print shops.
