Topics covered in the white paper include:
1. Contrast is the key
2. Contrast metrics
3. Limits of visual perception
a. Contrast thresholds (large targets)
b. Size matters: The visual angle
4. Watching your display screen from the right distance
5. Evaluation of display screen visual resolution
a. The simple case (RGB stripe sub-pixels)
b. The not so simple case (new sub-pixel arrangements)
6. The updated ICDM measurement procedure
As this report describes, the notion of display resolution is changing from the simple idea of counting RGB sub-pixels to a more sophisticated contrast modulation approach. The debate around this – and the need to develop improved metrology tools – has become more urgent as many new displays using sub-pixel rendering approaches entered the market and inconsistent resolution results were reported using the existing measurement standards.
The preeminent group working on display metrology, SID’s International Committee on Display Measurement (ICDM), has been tackling this issue for the last year – and continues to do so. Last May, the committee working on spatial resolution published a set of editorial comments and explanations to provide a safe basis for those using section 7.2 of the International Display Measurement Standard (IDMS) until a new version 2 is ready. The updated section 7.2 requires reporting of the Michelson contrast for the smallest grille line width to avoid obfuscation by application of thresholds for pass/fail decisions.
As suggested by the updated sections, version 2 of the IDMS will comprise the following details for even more complete and transparent specification of the visual resolution of display screens:
- Replacement of the modulation thresholds by specification of the luminance modulation as a function of achromatic grille line width (a modulation transfer function).
- Extension to grille patterns of primary colors in combination with black.
This paper is meant to introduce the background on the evaluation of visual display resolution and to present the procedure for its measurement according to the May 2016 updates of the IDMS which may be applied to non-standard subpixel layouts in a non-ambiguous way.
The white paper is available for free downloading HERE.