Density variations

Density variations between densitometers made by various manufacturers are due to technical factors, particularly the different filters used.

On devices made by the same manufacturer, there are normally only slight differences in readings, but the differences between different manufacturers can be considerable. Densitometers made by different manufacturers can produce different readings, even when correctly set. This also includes spectral photometers. FOGRA has published a report on this subject. Our recommendation is simple: use a color pattern to identify the readings and always state the device used along with the readings. Different devices produce different readings.

grapho metronic uses narrow-band interference filters. Unlike the gelatine filters which used to be used (Wratten broadband filters), glass filters have an almost unlimited service life.
Reproducibility is also significantly improved in the manufacture of glass filters.
Polarisation filters are also used in the measuring system. These suppress surface gloss. The first polarity filter (the polariser) restricts the direction of the light waves, which previously radiated in all directions, to a single plane. Light reflected on a wet or painted color surface retains this wave direction. This light is filtered out by the second polarity filter (the analyser), which lets through light perpendicular to the polariser. The polarised light which penetrates through to the paper is then diffused, which means that the light waves are reflected in all directions. The analyser then lets through only one wave plane of this light. This eliminates the gloss of wet or painted paper.
The polarisation filters also achieve greater linearity between the thickness of the coat and the measured density, which means a change in the coat thickness always produces an equal change in density.

The measuring sensors of the CCI systems are automatically compared at regular intervals to the built-in calibration fields before measurement.

The sophisticated measuring technology of the CCI guarantees high reproducibility. High density means good resolution.

CCI measuring systems have a very low variation between each other. This means that all the CCI systems around the world produce identical readings (within the stated tolerance range). Any greater deviation in a CCI can therefore be directly attributed to a malfunction.