They’re good for what they’re designed for, calibrating screens of known types.
A colorimeter has 3 filters (roughly red, green and blue) and measures the amount of each, then using a precomputed matrix for the type of screen, allows calibration to occur. It’s no good without the matrix.
A photospectrometer measures the power across the visible spectrum (the more expensive, the smaller the steps it measures) and allows you to measure the colour and luminance of anything it’s pointed at. It’s more accurate, can be used for more things, but significantly more expensive.
One use may be to measure a test chart under LED lights and then measure how accurately a display is showing those colours. Or to define the matrices for colorimeters.
As a (retired) analytical chemist I was quite curious about this post, then quickly learnt it was an inappropriate use of terms: a spectrophotometer is a type of instrument used in chemical analysis. As is a spectrometer.
What is needed appears to be a form of colorimeter, like a SpyderXPro for example.
That is where I got confused because I have spent the last five weeks teaching undergrad students how to use a spectrometer to measure blood analytes based upon absorbance and transmission. So I presumed the initial conversation was about color calibration for monitors.
Nope, spectrophotometers are also used for display calibration. So what is requested here is really a spectrophotometer, and not a colorimeter. Look at the ColorChecker Studio link which was given above. This is a spectrophotometer, not a colorimeter.
Colorimeters are actually quite limited. Not only are they less accurate and may not work as well on all types of displays and technologies (especially future, yet un-commercialized, screen technologies), but they can’t be used to calibrate printers, projectors… unlike spectrophotometers (which are therefore more versatile). Also colorimeters don’t grow old that well (especially because that’s often technology using filters which get bad with time; though there might be other technologies too, not sure), unlike spectrophotometers which should last you for years (unless you drop it on the ground, I guess! ).
Research labs do also use spectrophotometers, which are usually much bigger and more expensive (from what I saw), thus likely more accurate or maybe for even more specialized usage (I guess? I don’t really know, I never needed to use these, only assuming from seeing much higher prices), but computer graphics for sure also use spectrophotometers.
Different industries, so slightly different use of terms.
In graphic arts “spectrometer” typically means an instrument capable of measuring the visual range spectrum from media such as paper, as well as emissive sources such as displays and lighting. Media/reflection measurements will typically be 0/45 degree geometry using an equivalent of D50 light source (not often an actual D50 light source, but the measurements transformed to be as if it were.) Emissive measurements will typically be narrow angle for measuring displays, while a cosine adapter allows measuring ambient spectra from light sources. In graphic arts context a “spectrophotometer” typically means an instrument dedicated to measuring emissive only. A colorimeter on the other hand only measures XYZ values, by virtue of filters that mimic the standard observer spectral sensitivities. Since such filters are rarely perfect, it is normal to apply a calibration matrix when measuring a 3 primary additive display with known spectra.
The original question was about a spectral measurement instrument, not a colorimeter.
I’d say significantly different use of the terms. The wiki entry on spectrophotometry makes mention of a “spectrophotometer” being used in the graphics industry (and even has a picture of one in use!), but doesn’t discuss them much at all. Given that in chemical analyses, a spectrometer/spectrophotometer operates using transmitted light to perform a quantitative analysis, and the device mentioned in the wiki appears to be working on reflected light (and I doubt very much has a monochromator inside it), the two devices are clearly different. I can’t imagine why the term has been appropriated for two different things, but there you are.
One thing is certain: my Google searches didn’t yield anything in the first few pages that made reference to the devices used in the graphics industry, just the instruments used for chemical analyses.
I’ll let things lie as they are, I don’t wish to get embroiled in an argument here.
Lot’s of beers required after teaching Beer’s Lamberts law to student’s all day. And then to top it off after a full day of practicals on a Thursday I would do an evening class teaching students how to use Darktable. I get home about 9.30pm and beer is definitely on the menu.
The use of terms is the same, what changes is the exact capabilities of the instruments. A (light) spectrometer is any instrument that can measure a spectrum, i.e., measure light intensity vs. wavelength. It doesn’t matter the source of such light or the way the light is collected. A spectrophotometer is a spectrometer dedicated to measure transmission and/or reflectance (and in physics, for example, few would make the distinction, they’re all spectrometers).
So what is discussed here is really a spectrometer (when used to measure the spectrum emitted by the display) that can work as a spectrophotometer (when used to calibrate a printer).
The instrument in that picture can perfectly have a fully working spectrometer and light source inside.
In the lab we have grating spectrometers (without light source) significantly smaller than that with nanometer resolution over the full visible range. Unfortunately for the current topic, they’re research-grade instruments that cost above 5k USD…
Lab grade graphic arts/paint/material spectro’s certainly have scanning monochromators inside them. Lower cost, portable instruments use other technology - fixed diffraction grating spectrometers, discrete filter spectrometers (i.e. DTP-41 etc.), even reflection only mode instruments that use multiple narrow band illumination for the same overall function of measuring spectral response.
Because they all do spectral light measurement ?
[ As someone who once worked on scanning monochrometer and polychrometer optical emission chemical analysis instruments, I don’t find the use of the term to cover instruments with common underlying functionality all that surprising. ]
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