ISO 13656:2000 pdf download
ISO 13656:2000 pdf download.Graphic technology -Application of
reflection densitometry and colorimetry toprocess control or evaluation of prints and proofs.
tone control element, shall be within 1 % of the nominal value.
NOTE 1 For positive and negative polarity film control strips, it is desirable to add control patches with several tone values below 10 % and above 90 %, respectively.
NOTE 2 While it is recognized that the control element is specified as circular and actual work can be circular, square, elliptical, etc., the use of a specific shape enables process control checks across jobs, presses, and companies.
4.3 Preparations for measurements
Ensure that the measuring head and the sampling aperture of the instrument are clean. If necessary, observe the manufacturer’s warm-up time recommendations, then calibrate the instrument to read accurately relative to the perfect reflecting diffuser, according to the manufacturer’s instructions. Set the instrument to the desired mode.
Ensure that the sample is flat and not creased and place it on a flat, black surface which is in conformance with that defined in ISO 5-4 and ISO 13655 (namely a spectrally non-selective, diffusely reflecting material with an ISO visual density of approximately 1,5). Centre the sampling aperture, which should be smaller than the illumination aperture (as defined in ISO 5-4), on the middle of the control patch or spot to be measured. Ascertain that the instrument base and the sample lie in the same plane.
When reading a half-tone, the diameter of a circular sampling aperture should be not less than 15 times the screen width; it shall be not less than ten times the screen width. For the measurement of non-periodic screens the aperture shall be not less than 4 mm in diameter and for image elements greater than 30 pm should be even larger. The area of a non-circular sampling aperture shall not be smaller than that of the circular apertures defined above.
NOTE Where an aperture smaller than that recommended is used a number of readings should be averaged.
4.4 Measurement of reflection density and quantities derived therefrom
4.4.1 Instrument specification
The densitometer shall be in accordance with ISO 14981.
4.4.2 Data reporting
Any densitometric data shall be accompanied by a report specifying the exact conditions used. The report shall indicate conformance with this International Standard and shall include the following parameters:
– Densitometer manufacturer and model name
— Colour channel (K, C, M, Y, or wavelength in nm)
— Spectral response — shall be one of ISO Status I, T, E (as defined in ISO 5-3), DIN I, or DIN E (as defined in DIN 16536-2)
Polarisation (yes/no)
Sample backing (if not black)
Sampling aperture in mm
— Density values relative (substrate density set to zero) or absolute – Not required for values which depend on density differences only
Combined standard uncertainty (ISO 15790)
4.5 Measurement of colorimetric parameters
4.5.1 Instrument specification
The colorimeter, the conditions of measurement and the calculations shall be in accordance with ISO 13655. If a
tristimulus colorimeter is used, the measurement conditions (i.e. backing, geometry, etc.) shall be in accordance
with ISO 13655.
NOTE Some colorimeters also report density which is calculated from the spectral data. They may be fitted with polarisation filters. These filters are not recommended for use in the colorimetric mode of these instruments.
4.5.2 Data reporting
The reporting of colour co-ordinates shall be as specified in ISO 13655 and shall be accompanied by a report specifying the exact conditions used. The report shall indicate conformance with this International Standard and, in addition, shall include the following parameters:
— Colorimeter manufacturer and model name (specify if tristimulus photometric type)
— Sample backing (if not black)
Sampling aperture in mm
— Combined standard uncertainty (ISO 15790)
5 Test methods
5.1 Introduction
Each of the parameters determined from reflectometer data, which are deemed most useful for process control, are described in this clause. Where different methods for defining these parameters are specified the preferred methods are given first and their use is strongly encouraged in order to aid communication between users. Commonly available parameters which have not been defined in this document (such as densitometric hue error and greyness, print contrast and ‘Yule-Nielsen’ dot area) are not recommended as useful for general communication, even if they serve well for specific applications, and are thus not appropriate for this International Standard. Similarly, colorimetric density (usually defined as log (XdX); log (YdY) and log (ZdZ) where X0, Y0 and Z0 normally specify the reflectance factors or tristimulus values of the substrate) is also excluded since the spectral products do not conform to those specified in this International Standard.
Many of the parameters specified in clause 5, particularly those based on densitometry, are useful for process control but tell the user little about the appearance of the print. Many of these are appropriate measures for controlling a production run, others for defining the difference between proofs and prints and yet others for defining variation within a print. In addition clause 5 includes parameters which are used for some specific evaluation of printing performance (such as ghosting). Some of the parameters in clause 5 do have a colorimetric definition specified but densitometry is the predominant tool.
