Research on Color Contrast #10
Comments
|
Research list for APCA: https://git.myndex.com/ |
Specific to APCA:APCA Easy Intro
APCA linktree
APCA Reviewed
APCA on GitHubCLICK TO OPEN Links to APCA Related RepositoriesMyndex/SAPC-APCAThe Main Documentation Repository, also reachable as a webpage at git.apcacontrast.com Myndex/apca-w3The Code Repository for code and basic algorithms for use in practical guidelines. See also apcacontrast.com Myndex/bridge-pcaThe WCAG 2 backwards compatible bridge version. See also BridgePCA.com Myndex/deltaphistarDelta-Phi-Star is a simplified general purpose algorithm, that modifies ∆L* (delta-L-star) into a perceptual contrast for higher-spatial elements on displays. See also the seestars repository. Myndex/max-contrastMax-Contrast is a simple algorithm that automatically flips a text color between black or white, based on the background color, compatible with APCA. A11yReadTechInclusive Reading Technologies, the non-profit organization supporting research and development of readability technologies and related guidelines. Myndex/IlluminatedA repo collecting open public research notes and comments Myndex made regarding typography, CSS, color, contrast, and vision. Myndex/colorparsleyA lightweight but versatile mini-lib to parse color strings, objects, or numbers, developed for use with APCA-W3. Myndex/font-x-sizeUnder development, polyfill for setting font size based on x-height. Generally Related to contrast, reading, and impairments:CLICK TO OPEN Short Current BibliographyReading with low vision: The impact of research on clinical management (2011)Jan Lovie--Kitchin PhD School of Optometry Queensland University of Technology Luminance Contrast Using Color In Information Display GraphicsLarry Arend, with contributions from Alex Logan and Galina Havin Human factors design standard (HFDS) (2003)Federal Aviation Administration (FAA) An Engineering Model for Color Differences as a Function of SizeM.Stone, D.Szafir, and V.Setlur Comparing the Shape of Contrast Sensitivity Functions for Normal and Low VisionS.Chung and G.Legge Psychophysics of Reading (I, II, V, VI, XV, XVIII, XX)G.Legge, D.Pelli, G.Rubin et alia Color Appearance ModelsM.D. Fairchild Realities and Myths of Contrast and ColorA.M.Somers Colorimetry: Understanding the CIE SystemJanos Schanda, CIE Does print size matter for reading? A review of findings from vision science and typographyG.Legge, C.Bigelow Model for the spatial contrast sensitivity of the eyeP. Barten Computerized simulation of color appearance for dichromatsH.Brettel, F.Viénot, J.Mollon
|
Color and Contrast OutcomesThis had been posted in the old Silver repo, adding it here as it directly relates. Color, as in hue and colorfulness, is distinctly separate from luminance, which is "colorless" spectrally weighted light. It's convenient to think of luminance as a black & white TV set, and to think of color as just the small amount that's added to that black-and-white signal. Because that's literally how the human vision system processes it as well, and the separate components of luminance and color serve different purposes in our neurology.
NOTE: The fact that contrast sensitivity is dictated by spatial frequency is a matter of peer-reviewed scientific consensus dating back to the 1960s. ⁵Click for additional backgroundLuminance carries the high spatial frequency information such as text, and color (hue) exists in the very lowest spatial frequencies. "...reading speed depends on the spatial frequency and contrast of the text. When text contrast is low, reading speed shows strong spatial-frequency dependence..." ⁴ Visual presentation properties such as line spacing affect spatial frequency and therefore directly affect contrast and readability. Currently they are in a different area, but they belong as part of the overall visual contrast/visual hierarchy group. DataViz and nontext are often at low spatial frequencies, and use of color for data coding is related closely to DataViz, but not particularly related to visual contrast for readability. Meanwhile, reading requires good luminance contrast, without regard to color as in hue. (An exception is rejecting pure red paired with black or dark colors, note that APCA essentially does this naturally anyway, as read on black is actually bad for standard vision as well).
Some of the other adds:Text zoom, Text use-cases, non-text use-cases, text in an SVG, contrast for images of text/logos. Click for additional backgroundThese were some editorial adds made to the Google doc along with comments. I did not delete any lines from the other areas such as visual presentation, but I did leave comment notes at those in the document.
For convenience, here are the tables relating to color and visual contrast from the Google doc as split / combined into these two guidelines: Guideline: Content does not rely on color alone to convey meaning, uses sufficient contrast.
Scope: Item or ViewExpertise Needed:
Guideline: Visually readable content uses ample luminance contrast.
Scope: Item or ViewExpertise Needed:
Thank you for reading. A general reference for a crash-course in color and contrast: The Realities And Myths Of Contrast And Color Footnotes
6) Click for refs & discussion of text use casesText Use Cases
NON Text Use CasesRegarding nontext use cases, one set is:
So another idea for non-text use cases is: Semantic, Symbolic, DataViz, Container SEE: 7) Click for refs & discussion of characters per line"80 characters per line" is a somewhat unsupported value pulled out of thin air. The history of 80 characters has much to do about the economics of IBM's equipment back in the day, than it has to do with any actual readability research. In other words, asserting lines should be 80 is pseudoscience. Lines of code can reasonably be much longer and there's a number of arguable reasons to not have line breaks in code. But 80 characters is usually too much for columns of body text, which should be much shorter, and this varies per language and writing system. "...The 66-character line (counting both letters and spaces) is widely regarded as ideal...." It could be non-normative and informative. the best practices recommendation for columns to have an average line length of 50 to 70 characters (for latin-based).Other languages need an expert typographer in that specific language to work on certain international outcomes. 8) Click for discussion of body-text justificationFor web content, columns of body-text must be:
It's important recognize that full-justification requires the judgment of the eye of a skilled typographer in order to make it work. Web content is responsive and interactive and changes position. Like all automatic adjustment systems it does not benefit from human intervention, and the automated systems for things like text reflow in a browser are not nearly at the level they would need to be to accomplish appropriately set full justification. That said, central justification of body text is even worse for reading, because the beginning of each line is that a different place that makes it very difficult for the eye to scan back to the beginning of the next line. And also, all of this is for body text. These rules do not and should not apply to two or three lines of much larger headline text as an example. On that note, the use case for body text is very different from the use case for any other form of text on a page. 9) Click for refs & discussion of line-heightThis is from another unsupported SC which originally says something like "must be 1.5 times the line height". This is practically meaningless in CSS, because what's important is the distance between glyphs, and for Latin alphabet for instance, that's going to be between lowercase Lines, and the x-height ratio to font-size is vastly different depending on the font family, by as much as ±50% or more. It could be non-normative and informative.While I revised it for now to be 2.5 times the x-height, i.e. This goes for paragraph spacing as well, is there a number of ways to indicate paragraphs including indenting out outdenting, and it is out of scope for a law to say that you must use paragraph spacing as opposed to indenting as an example. These arbitrary values are really notwithstanding, as the reality is much more nuanced. Nevertheless, it is well known though is that the spatial frequency and the effects of crowding are very important readability, but you can't make a blanket statement on how much letter or line spacing needs to be added, as that is a function of every individual font design and every individual font design is going to need something different. Blanket arbitrary values do not work hereEspecially not in a guideline that is intended to become law at some point. Some related references: D.Pelli et alia Crowding and eccentricity determine reading rate
|
Partial BibliographyThe following references are selected early work product Organized into clickable sections to keep it more manageable. CLICK FOR Key References
Key ReferencesBrightness function: Effects of adaptation Brightness Perception in Complex Fields A Technical Introduction to Digital Video Gamma and its disguises: The nonlinear mappings of intensity in Color Appearance Models In color perception, size matters An engineering model for color difference as a function of size Adaptive luminance contrast for enhancing reading performance and visual comfort on smartphone displays The CIE DE2000 Color-Difference Formula: Implementation Notes, Supplementary Test Data, and Mathematical Observations Effects of chromatic and luminance contrast on reading. Psychophysics of reading. XI. Comparing color contrast and luminance contrast. Colour and luminance contrasts predict the human detection of natural stimuli in complex visual environments CLICK FOR Neurological / Visual Cortex
Neurological / Visual CortexThe Empirical Characteristics Of Human Pattern Vision Defy Theoretically-Driven Expectations Chromatic And Luminance Losses With Multiple Sclerosis And Optic Neuritis Measured Using Dynamic Random Luminance Contrast Noise. First- and second-order contrast sensitivity functions reveal disrupted visual processing following mild traumatic brain injury Representation of Surface Luminance and Contrast in Primary Visual Cortex CLICK FOR Monitor Technology Related
Monitor Technology RelatedHuman factors design standard (HFDS) Using Color In Information Display Graphics Color Usability On Air Traffic Control Displays Perceptual Display Calibration Electronically / Optically Generated Airborne Displays A Multiscale Model of Adaptation and Spatial Vision for Realistic Image Display CLICK FOR Psychophysics
Psychophysics“Symmetry and constancy in the perception of negative and positive luminance contrast” Psychophysics Of Reading II. Low Vision Color Improves Object Recognition in Normal and Low Vision Perceived image contrast and observer preference I. The effects of lightness, chroma, and sharpness manipulations on contrast perception Spatial-Frequency And Contrast Properties Of Reading In Central And Peripheral Vision Edge-Aware Color Appearance Perceived contrast in complex images Tone Mapping Algorithm for Luminance Separated HDR Rendering Based on Visual Brightness Functions Viewing distance requires large characters to ensure legibility on TV-set. The effect of font and line width on reading speed in people with mild to moderate vision loss The Effects of Font Type and Spacing of Text for Online Readability and Performance Recognition versus Resolution: a Comparison of Visual Acuity Results Using Two Alternative Test Chart Optotype Luminance contrast sensitivity for achromatic and chromatic parafoveal stimuli under mesopic conditions (Mesopic visual function in healthy and Aged-related Macular Degeneration (AMD) subjects: relating structure to function) Spatial Contrast Sensitivity Vision Loss in Children with Cortical Visual Impairment Spatial-frequency bandwidth of perceived contrast **Psychophysics Of Reading: XI. Comparing Color Contrast And Luminance Contrast ** CLICK FOR Clinical And Experimental
Clinical And ExperimentalReading in low vision Determining magnification for reading with low vision Effect of room illuminance on monitor black level luminance and monitor calibration. Rethinking ADA signage standards for low-vision accessibility Spatial-frequency and contrast properties of reading in central and peripheral vision Human Computer Interaction: Legibility and Contrast Letter case and text legibility in normal and low vision Psychophysical contrast calibration Guidelines for Using Color in Voting Systems Contrast sensitivity of the human eye and its effects on image quality Positive and negative polarity contrast sensitivity measuring app Visual Calibration and Correction for Ambient Illumination CLICK FOR Color Vision Related Resources
Color Vision Related Resources**A Clinically Accurate Color Blind Simulator** using the peer reviewed Brettel/Viénot Model. This is a simulator of Color Vision Deficiency (CVD, sometimes inaccurately called "colorblind"). It allows processing your screenshot and shows multiple types of CVD at once. Site includes a biblipgraphy and additional discussion and explaination. Spectral Sensitivity of Color-Blind Observers and the Cone Photopigments Response Functions for Types of Vision According to the Muller Theory CLICK FOR Interesting Concepts in Improving Accessibility
Interesting Concepts in Improving AccessibilityAccessibility for Individuals with Color Vision Deficiency Improving Discrimination in Color Vision Deficiency by Image Re-Coloring Enhancing Color Representation for the Color Vision Impaired Increasing Accessibility for Map Readers with Acquired and Inherited Color Vision Deficiencies: A Re-Coloring Algorithm for Maps Information Preserving Color Transformation for Protanopia and Deuteranopia Contour Enhancement Algorithm for Improving Visual Perception of Deutan and Protan Dichromats |
Some key graphicsThese graphics were developed to help explain some of the concepts involved in vision, contrast, and readability. Visual PresentationContrast Sensitivity CurveThis is the human contrast sensitivity curve. The grey sample fonts are all at the exact same color of CVD aka colorblindThis shows standard vision upper left and then different forms of color insensitive to demonstrate the colors that they can see and not see. Dark Mode ComparisonThis comparison shows WCAG2 text on the left and APCA on the right, with minimums in dark mode, only the APCA text is easily readable. Font-Smoothing can be badin this graphic a thin font is shown with WebKit font smoothing antialiased or in auto, an anti-aliased, much of the font is subsumed into the background making the font thinner in weight and therefore lower in contrast. In auto the contrast is improved because the weight is not damaged as much, and it is still smooth because default anti-aliasing is more than sufficient for small fonts. Font-size is inconsistentThis graphic shows the font Verdana at 14px and the font Times New Roman also at 14px, showing that even though they are both set to the same exact font size, Times new Roman is substantially smaller as rendered to the screen. Screen Pitch at CSS Ref pxThis chart indicates the screen pitch for the CSS canonical measurement px to equal 1.278 arc minutes. WCAG to APCAThis shows the functional similarity between WCAG2 contrast values and APCA Lc values, measured near center contrast. Critical Font Size TableThis is a table that indicates the critical font size for best readability at different levels of visual acuity. Critical Print SizeThis graph from research of Lovi-kitchin shows the contrast reserve and critical contrast. |
|
Thank you for highlighting and centering the disabled perspective with this issue—it is really appreciated. I've been doing some research on the academic end of things, and am in the process of performing outreach to individuals whose domain expertise may be applicable for this concern. I am posting this to communicate that work is occurring here, with the hope that it keeps this issue open until I can either make introductions or come back with no interest expressed from the people I am reaching out to. Part of this is the translation layer, where these individuals may not be aware of/participate in GitHub or WCAG. I am hoping my outreach communication helps with this aspect. |
This issue is to gather research on color contrast. If you have links to color contrast research or are aware of individuals working in this space, please note that here.
Peer reviewed research studies on readability by people with disabilities are particularly valuable.
Please keep this issue clear of discussion and debate. It is meant to collect resources.
The text was updated successfully, but these errors were encountered: