Measuring Color

MEASURING COLOR

While there is an art to designing for and selecting the right colors, there is definitely a color science, and that means color can be measured. Scientific measurement of color output enables greater control in the print production process.

Translating color into mathematical calculations based on data generated by measuring devices eliminates the need for a press operator to “eyeball” the press sheet to see if it looks approximately right.

Color measurement instruments are able to receive color data in the same way our eyes receive color -- by gathering and filtering light that is reflected from an object, whether that object is a flower or a sheet of paper printed with offset inks or toner.

The measurement device; however, transforms the color into a numeric value that allows us to scientifically analyze the quality of a specific color object.

There are three different devices used to measure color characteristics, and each has its role during the color workflow and production process.

These devices are colorimeters, spectrophotometers and densitometers.

Colorimeters

Colorimeters measure colors using filters to determine the nature of the color. In the world of graphic communications, colorimeters are most frequently used to calibrate output devices, including monitors, printers and even LCD projectors.

A colorimeter can sometimes be used as an alternative to a spectrophotometer, but it is not as accurate. In scientific fields the word generally refers to the device that measures the absorbance of particular wavelengths of light by a specific solution.

Colorimters are far more useful in the chemistry of color, such as formulating inks and toners, than they are in the practical color management of your print devices.

Spectrophotometers

A spectrophotometer measures wavelength reflections. A light source shines through or on the item being measured, such as a printed sheet, and a detector detects how much light has been absorbed by the area of the printed sheet being measured. This absorption is then converted into a number, which can be analyzed by a computer.

A spectrophotometer (also called spectroreflectometer or reflectometer), takes measurements in the visible region (and a little beyond) of a given color sample. If the custom of taking readings at 10 nanometers (billionth of a meter) increments is followed, the visible light range of 400-700 nm will yield 31 readings. These readings are typically used to draw the sample's spectral reflectance curve (how much it reflects, as a function of wavelength). Spectrophotometers are considered to be the most accurate technology available for measuring color characteristics.

An example of a spectrophotometer is the EFI ES-1000 spectrophotometer.

Another is the iPublish Pro 2.




Densitometers

A densitometer measures color ink or toner density. Densitometers are usually used in offset printing. Because inks are known standards, a densitometer helps in controlling the amount of ink on a page and the resulting color.

Color standards, such as the standards delivered by Pantone, include ink densities as part of the color specification.


XRite makes a fine densitometer.

BabelColor has a fun online densitometer that you can play with, or use for serious color management purposes.

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Email me at reilley4color@gmail.com