RE: Study: The effect of serifs and stroke contrast on low vision reading

Dear all

Indeed, the effect is called visual stress, so if you're looking for research papers on the topic then that is the term to search for. It affects some people more than others, and the effect depends on the colour of the text, but the colour that causes the least visual stress is different for different people. I have worked with Arnold Wilkins on several projects and he has done lots of research in the area, like this
https://www1.essex.ac.uk/psychology/overlays/2021-262.pdf

Lowering the lightness contrast reduces the excitation that causes visual stress, but that's in a relative sense reducing it from pure black on pure white, down to some intermediate level of contrast. Obviously there is a trade-off here because if you reduce the contrast too much you then get eyestrain because of visual system is working too hard to perceive the text. It generally helps to have the text a little bit larger and the contrast a little bit lower, but then there is another trade-off because if the text is too large then the characters per line reduces, and the eyes have to spend comparatively more time tracking backwards and forwards, which reduces reading speed.

I believe the APCA guidelines suggest Lc between 60 and 90 for body paragraphs of text, and the font-size should be pretty close to 16 px, and the font-weight should be normal (400) (for a font with a well behaved x-height, and stroke thicknees, like Arial / Helvetica). I wholeheartedly support this as being a pragmatic recommendation that offers a reasonable middle ground between the extremes.
Of course, some people need to customise the appearance of text so that the contrast is perhaps higher, or indeed lower, and use a particular colour combination. I currently believe that supporting Windows high contrast mode is a better approach than attempting to offer custom colour combinations within a particular website. Although the default settings of windows high contrast mode are somewhat garish, they can be customised, and I have customised mine to my own personal taste, so it's no longer particularly high contrast.

Happy to chat further on this topic, it's a shame that the project to write some better guidelines on this topic appears to have been abandoned.

Best wishes

Sam Waller (he, him)
University of Cambridge, Engineering Design Centre
01223 332826

From: Jon Avila <jon.avila@levelaccess.com>
Sent: 02 January 2023 23:23
To: public-low-vision-a11y-tf <public-low-vision-a11y-tf@w3.org>
Subject: RE: Study: The effect of serifs and stroke contrast on low vision reading

Hi Andrew, I understand what is being said about low contrast stroke.

When I speak to people who prefer low contrast (lightness) text - I believe it's not about recognition of the text but about the impact that high contrast has on the visual system.  Some people report that high contrast patterns can cause migraine like symptoms.  So it's more about the impact which prevents them from staring at high contrast lightness text.

Jonathan

From: Andrew Somers <andy@generaltitles.com<mailto:andy@generaltitles.com>>
Sent: Monday, January 2, 2023 3:04 PM
To: Laura Carlson <laura.lee.carlson@gmail.com<mailto:laura.lee.carlson@gmail.com>>
Cc: public-low-vision-a11y-tf <public-low-vision-a11y-tf@w3.org<mailto:public-low-vision-a11y-tf@w3.org>>
Subject: Re: Study: The effect of serifs and stroke contrast on low vision reading

And to follow up my previous post I wonder if misunderstandings relating to the meaning of "font-stroke-contrast" versus actual "visual contrast" is what led to this weird myth that seems to persist on the internet today, claiming that "some people need low contrast text".

???

I have been searching for credible research that might affirm the assertion "some people need lower contrast" but I'm not finding much relevant ... And I am increasingly thinking, that some may have read "low contrast font" in some paper but are misinterpreting it to mean low contrast colors, when it actually means having a font with a more uniform stroke width.



On Jan 2, 2023, at 11:40 AM, Andrew Somers <andy@generaltitles.com<mailto:andy@generaltitles.com>> wrote:

Thank you Laura, that's a very interesting study, and directly echoes my personal viewpoint on this particular subject.

I want to make a note here for anybody that reads this study:

The study uses the term "stroke contrast". It's very important to recognize that in the context that they are using it, stroke-contrast relates to the variation in stroke within a particular glyph.

And the effect is exactly opposite of the actual visual contrast.

In other words in the context of font contrast as in the stroke-contrast within a glyph, e.g. Times New Roman has very high stroke contrast.

But the visual contrast of Times is lower than that of Helvetica. Helvetica, having a uniform stroke width therefore has a low stroke contrast but (perhaps counterintuitively) that results with its visual contrast as higher.

Here's an example:

<Screen Shot 2023-01-02 at 11.35.14 AM.png>



On Dec 27, 2022, at 8:17 AM, Laura Carlson <laura.lee.carlson@gmail.com<mailto:laura.lee.carlson@gmail.com>> wrote:

Fyi:
https://www.sciencedirect.com/science/article/pii/S0001691822003250<https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS0001691822003250&data=05%7C01%7Csdw32%40universityofcambridgecloud.onmicrosoft.com%7Cf377848b27cc4f2ac1a108daed1845e5%7C49a50445bdfa4b79ade3547b4f3986e9%7C1%7C0%7C638082985753551240%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=aUfnwXnjIOkgxEk45AVmP2gWmUePtVKSxisNsUypdpk%3D&reserved=0>

Kind Regards,
Laura

--
Laura L. Carlson