ISO 13656 pdf download – Graphic technology – Application ofreflection densitometry and colorimetry to process control or evaluation of prints andproofs.
3.15
mid-tone balance control patch
a hail-tone control patch, contain4ng all three chromatic process inks, used for assessing the balance between the
inks; the cyan tone value is normally in the range between 40 and 60 and the magenta and yellow tone values are
selected to approximately prockice an aclvon,atic colour
3.16
non-periodIc halt-tone
image in which the elements composing it do not have a regular frequency
3.17
OK print
OK sheet
during production printing the production prwit singled out as reference for the remaining production run
[ISO 12647-1J
3.18
overprint
condition where two or more layers of colorant, usually Ink. are printed on top of another
3.19
print substrate
material bearing the pnnted image
[ISO 12647-1)
3.20
process colours (for four-colour printIng)
yellow, magenta, cyan and black
[ISO 12647-1)
3.21
reflectance factor
ratio of the measured reflected flux from the specimen to the measured reflected llux from a perfect-ref lecting and perfect-diffusing material located in place of the specimen Unit: 1
[ISO 5’4J
3.22
reflection density2)
reflectance factor (optIcal) density3)
logarithm to base ten of the reciprocal of the reflectance factor. Unit: I
3.23
ref lectometer
photometer for measuring quantities pertaining to reflection
[International Lighting Vocabulary 845-05-26]
The control str shal contain doubling5Iur patches as well as 5sngIe-colour and overprint patches for the process colour solids, namely K, C. M, V. (C.M). (C+Y). (M÷Y) and (G+M.V). In addition it shall contain at leasi 3 well-defined single colour half-tone control patches, labelled with their nominal tone values, fr each of the process colours K, C. M and V. One shall have a tone value between 20 % and 30 %. another shall have a tone value between 40% and 50% and the third shal be between 70% and BO %. There shall also be a well-defined half-tone control patch for the measurement of mid-tone balance and an area close to, or within, the control strip tor measurement f the unprinled substrate. The complete control strip should be repeated as frequently as possible across the whole width of the press sheet.
The halt-tone dot shape of the image elements used for process control shall be circular and the screen ruing should lie within 10cm 1 of the screen frequency of the subject Images. All tone values. Including those of the mid- lone control element, shall be within I % of the nominal value.
NOTE 1 For positive and negative polarity tilm control slrs, Ills desirable to add control patches w,lh several tone vatues below 10% and above 90%, respectively.
NOTE 2 While I Is recognized that the control element e specified as circular and actual wed can be circular, s,iare, ellçtical, etc., the use of a specific shape enables process control checks across jobs, presses, and comparwes.
43 Preparations for measurements
Ensure that the measuring nead ana ;l-.e 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. tfusely 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 Im should be even larger. The area of a non-circular sampling aperte shall not be smaler than that of the circular apertures defined above.
NOTE Where an aperture smaller than that recommended is used a n..inber 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 condeions used. The report shall indicate conformance with this International Standard and shall include ttie following parameters:
Densitometer manufacturer and model name
— Colour channel (K. C, U, V. 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).
ISO 13656 pdf download – Graphic technology – Application ofreflection densitometry and colorimetry to process control or evaluation of prints andproofs
