International hydrographic organization specifications for chart content and display aspects of ecdis
Set-up for measurement Important -
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S-52 Appendix 2 - IHO
| Set-up for measurement Important - These measurements are very sensitive to stray light entering the experimental area, and inaccurate results will occur if special care is not taken. All measurements should betaken with the measurement area properly shielded against stray light. The measurements are best taken with light absorbers in place around the monitor and measurement apparatus. A black felt drape over the measurement area works well. Care must betaken by the operator that his clothing does not reflect light back into the measurement area. B Monitor setup The monitor must be adjusted to its calibration conditions. (See section B. This means the controls are set to its calibration position i.e. black (CHBLK) on the screen is 0.52 cd/m² or below and a white square (CHWHT) on the screen has a luminance of 80 cd/m² (note that if the tolerance of luminance is 20%, then the acceptable range of CHWHT is from 64 to 96 cd/m²). This ensures that the monitor is setup as closely as possible to its factory settings, and the colours will be as close to calibrated values as possible. B Principal colour producing element chromaticity measurement The Chromaticity (colour coordinates) of the principal colour producing elements is measured using the procedure outlined in BB Luminance/radiance meter setup The luminance or radiance meter should be secured so that it measures the same part of the screen for all measurements. A suction cup with hanging bracket works well. The measurement area of the luminance meter should be well within the square of the test colour. B Measurement procedure This procedure is well suited for automation. Under software control, the test patterns can be generated, and the output of the luminance meter recorder, and colour x, y, and L data calculated 66 S, Edition 6.0 March 2010 1. Setup the software so that it generates the test patterns and colours. The test pattern should be a square of size approximately 5 cm per side. The software should cycle through the colours in the particular colour table being verified. The Red, Green, and Blue colour components for each test colour should be sent to the monitor separately. 2. Measure separately the luminance of each of red, green, and blue for each colour of each table to be tested. In the crudest sense, this is accomplished by disconnecting the two colour channels that are not being currently measured. Under software control, this can be more elegantly controlled, where the computer that is creating the colour test square will send only the individual colour components to the monitor screen one at a time. 3. The luminance of each colour is calculated by using the calibration factor for each colour that is derived under section B above. 4. Calculate the x, y, and L for each colour measured using the procedure outlined in section BB Measurement verification The measurements must be within required limits of each colour, as specified in section 5.2.3 of this document, "Colour Conversion Tolerance. The following colour pairs of the BRIGHT_SUN colour table have a E of <20. In order to allow for measurement errors, which might put them outside the tolerance limits, they are exempt from the colour separation tolerance test which requires a ΔE* of >10. Download 0.98 Mb. Share with your friends:
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