ISO TS 20793:2019 pdf free download – Photography一Lenticular print for changing images – – Measurements of image quality.
For the standard conditions, hemispherical illumination shall be applied. The illumination spectra shall be a stable and spectrally continuous broadband visible light source, for example, an incandescent lamp defined as CIE Standard Illuminant A.
5.4 Light measuring device (LMD)
The light reflected from the lenticular print shall be measured. Illurninant D50 shall be applied. The following requirements are given for measurement instrument:
a) The spectroradiometer shall be capable of measuring spectral radiance over at least the 380 nm to 780 nm wavelength range, with a maximum bandwidth of 10 nm for smooth broadband spectra.
Care shall he taken to ensure that the LMD has enough sensitivity and dynamic range to perform the required task. The measured LMD signal shall he at least ten times greater than the dark level (noise floor) of the LMD, and no greater than 85 % of the saturation level.
b) The LMD shall be focused on the image plane of the print and aligned perpendicular to its surface, unless stated otherwise.
c) The relative uncertainty and repeatability of all the measuring devices shall be maintained by following the instrument supplier’s recommended calibration schedule.
d) The recommended measuring distance is between 35 cm to 60 cm. The measuring distance shall be noted in the report.
The precise alignment of the lenticular lens and the printed lenticular image is essential. The procedures for the printing of high quality lenticular images are described in Annex B.
7 Measurements and calculations
7.1 General
This document specifically describes the measurement methods of the density and the evaluation methods for the following critical attributes of lenticular prints for changing images:
a) cross-talk of lenticular images;
b) viewing direction angle range of a lenticular image;
c) divergence from the designed viewing direction angle of the main lenticular image;
d) uniformity of the image within the printing area.
These attributes are critical for high quality lenticular prints for changing images. These items are measured by changing the angle of the print to the plane of the light measurement device (LMD).
7.2 Measurements of angular dependence
The measurements of the viewing direction dependence of density shall be done using the measurement system described in Clause 5.
For black and white images, all white patches, all black patches, and patches with a micro-striped pattern that are illustrated in Figure 4 and Tables 1 or 2 shall be measured. For colour images, the black striped pattern shall he replaced with a primary colour, i.e. yellow, magenta, or cyan, or with a secondary colour, i.e. red, green, or blue.
The reflected light from the lenticular print shall be measured from the normal direction of the print. Then, the print shall be rotated as shown in Figure 1 or Figure 2. The reflected light shall be measured in intervals of 2° from —45° to +45°.
The visual density shall be calculated with Formula (3), in accordance with Iso 5-3 and ISO 5-4.