X-Rite i1Display Pro Plus

Calibrators come in two main types:

Colorimeters - can only read light emitting devices, like monitors. They are generally the best (and most affordable) option for calibration monitors. Essentially these are like simple digital cameras with a sensor and some filters in front of the sensor to separate the different colours of light.

Spectrophotometers - These measure the actual spectral wavelengths of light. They have their own light source so can handle both light emitting devices like monitors and reflective materials like paper. They're very good at print but not as good as colorimeters for monitors generally, as the commonly available models tend to have some difficulty reading deep shadows on monitors.

A third type 'Spectrocolorimeter' - is something Datacolor came up with in their print calibrators. We at Image Science are ...not huge fans.

Here's a more comprehensive overview of the different types of calibrators (paraphrased from the ColorSync mailing list!):

1) Radiometer is a sort of light meter for some assumed spectrum; could be any electro magnetic radiation (EMR). If it is used for photography it's literally called a Light Metre.

2) Spectrometer is a radiometer that can report spectral power distributions, e.g., the EMR contour of a spectra. This is classically about a prism, hot objects and the visible signatures of their elemental constituents. But also could be about any range of EMR.

3) Spectroradiometer - measurement of precise energy distributions across a spectra. This is about knowing not only the spectral distribution, but exactly how much power is being conveyed.

4) Spectrophotometer, is an application of a spectrometer for evaluating spectral power distribution in range of visual sensation. In domain of Colorsync Users, this tends to be optimised for reflective media, but such a distinction is application dependent.

5) Colorimeter, a device that reports tri-stimulus colorimetric (e.g, CIEXYZ) coordinates of spectra; optimised under an assumption of RGB emissive media, i.e. display technologies

These last two are applications most relate to colorimetry, whereas the former three apply to many other EMR domains. So if you're a physicist or chemist or radio engineer, for example, you are generally thinking in terms of first 3, and if you are a colour user/engineer you are thinking mostly in terms of the last two.

Calibrators have filters in them and depending on the characteristics of the displays they are measuring, they may or may not support that type of display.

The display types are:

• CRT - Cathode Ray Tube - these are the older type of screens, the large thick monitors of yore with thick glass over the screen. Almost all of these are retired now.
• LCD - Liquid Crystal Displays - the modern flatscreen monitor. Available with two different types of backlighting technology - fluorescent and LED.
• OLED - An emerging technology, Organic Light Emitting Diode. Not many monitors are OLED yet, although we are now seeing laptops with them coming through. It's expected these will grow in popularity in coming years. Very high end TVs are now often OLED based.
• Plasma - No longer made, these were a wonderful quality display technology used for TVs
• Front Projector - Popular in home cinemas and board rooms everywhere!

What colour temperarture choices for white point does the system allow you to make?

At a minimum, 6500K and monitor native should be offered. 6500K is the standard whitepoint in general use in the photographic world, and lower end monitors don't like having their whitepoint adjusted so monitor native is the best to use in those cases.

However, ideally you can set any whitepoint you like, so that you can, for instance, adjust your monitor to look more like specific paper types.

What gammas can you choose when calibrating?

Pretty much everyone should be using 2.2.

Some might want to experiment with L* in some obscure cases.

How many patches are used (measured) in the calibration process? More (to a point) is better from a quality point of view, although it makes the process take longer of course.

200 to 400 patches is generally enough.

Also - can the calibrator target the reproduction of specific colours, such as specific Pantones?

Uniformity is still an issue with modern LCD monitors, especially lower quality ones. Does the calibrator have a system for assessing the screen uniformity?

(Unfortunately there's no system for correcting screen uniformity issues, other than getting a better monitor!)