Measurement Types

There are many conditions under which measurements can take place, and these conditions affect the measurement results in various degrees. For those taking measurements, it is important to have a record of what was going on when the measurement was taken, in case failed measurements can be traced back to inconsistencies. For those designing standard operating procedures, a thorough knowledge of what conditions are likely to change the results of measurements is essential.

M-series Conditions

Among the conditions under which measurements are taken, we record any filtering that is used according to ISO 13655-2009. The industry commonly recognizes 4 measurement modes:

• M0 - Illuminant A (UV is included) (Unfiltered tungsten) most historical instruments

• M1 - Non-polarized light Illuminant D50 (CIE D50) (300 - 780 nm)

• M2 - Any non-polarized light with UV-cut

• M3 - Any light that is polarized and is assumed to have some UV-cut

Reflective and Transmissive

Reflective color measurement measures color as reflected off of the surface of a medium (ie: ink on paper).

Transmissive measurement measures color on a clear or semi-opaque medium as light is passed through it. Much back-lit signage features transmissive color and can best be measured using a transmissive-measuring instrument, like a Barbieri LFP/qb.

Aperture Size

The aperture of a measuring instrument is the opening through which light passes into the sensing elements. The aperture size of a measuring instrument can greatly affect measurement results. For media with a flat, even surface, a relatively small aperture is sufficient to achieve a uniform sample. Larger aperture sizes are preferred when measuring color on canvas and other fabrics, as well as other uneven surfaces. The larger aperture size ensures that a large portion of the material is sampled and the true color is correctly represented.

Popular instruments and their aperture sizes:

Note that the minimum patch sizes required for all measuring instruments are significantly larger than the aperture size.

Scan Instrument Functions

Single Patch

Some instruments allow for the measuring of a single patch, either for grabbing single samples, doing spot checks or for measuring an entire chart with great precision.

Strip Hand Scanning

Instruments like the i1Pro 3 or the Spectrodens are made for hand-held use. The instrument is slid across a row of patches by hand, sometimes with the aid of a ruler to aid in tracking.

Sheet-fed Scanning

The MYIRO-9, Swing and iSis measure an entire sheet of color patches at a time. The sheet is fed into the front of the instrument and it takes over the advancing and measuring of each row automatically. Sheet-fed scanning is generally considered to be more accurate and consistent than hand-scanning. Some sheet scanners also recognize bar codes printed with the target patches, aiding in gathering meta data and routing measurements.

Full-page Table Scanning

Table-style instruments like the I1 iO and the Barbieri LFP/qb have flat page holders and move either the measuring head (iO) or the entire page (LFP) to measure patches or regions from the page. They’re often the better choice for measuring flexible or flimsy targets such as thin plastic films and fabrics or thick / rigid samples.