Wayne you're out of line Re: A BRIEF ENCAPSULATION OF USER VISUAL NEEDS

Hi Wayne. What are you doing?

No, my information is not out of date.

Wayne, you're referencing things out of context when you don't even know what the context is. It is beyond infuriating, and your assertions are meritless.

The information in my post that you are attacking is based on current international standards, and the most recent research.

But here's the really funny thing (at least I'm trying to laugh as opposed to being angry) the paper that you're claiming is most recent: "Does Print Size Matter” Legge, Bigelow is from 2011 and it is a REVIEW paper of the last 40 years of research and not new experimental research! So please don't try to make some spurious claim that it's somehow superseding previous research, when in fact it is a review of previous research. You're an academic, you should know better.

But here’s the most hilarious part: I read and cite Legge et.al. frequently, INCLUDING this exact paper. I read it over three months ago. In fact It's one of the papers that will end up in the bibliography. And it’s the paper that led to the work we are doing in terms of aligning font metrics based on x-heights among other things. 

I actually read this paper, and I actually understand it. However I’m not sure you do as you made several meritless statements deriding the very rough draft of an outline that I had posted (and which I posted for an unrelated issue). Your statements indicate a misunderstanding of the underlying material. While of course your comments were infuriating to say the least, I am trying to take a proactive approach to explain the body of knowledge to you and hopefully correct misunderstandings for you and anyone else reading. If you realize


I’m Not Researching Printed Books.
And printed material is not really what I am talking about. That posted outline is unrelated to any of your comments. Nevertheless, as I stated in the post, it is a very ROUGH draft and it is NOT a published report. I posted it in response to a user that was making a lot of unfounded assertions.  My intent was to (hopefully) give him a little more information as to what issues are at stake as that user was clearly misunderstanding a lot of things and stirring things up as opposed to being constructive.

And importantly, I was never referring to "16 inches to the stimulus". That is more generally about reading printed words on paper, such as in a book. The research I am doing involves emissive displays (computer monitor) — and 16 inches is not necessarily the appropriate distance for displays, but still that has nothing to do with what I was discussing in that post. 

Again, you are way off base and out of context. At that instant I was discussing comparative acuity levels. That would be the meaning of the line were I say:
Classification of Acuity can be divided into three broad groups:
Notice I did not say critical print size, though we do have original research on that pending.

> Wayne Said: Here is the math. The normal acuity limit at 16 in. is around 4.5pt with really clean eye chart font. Double that an you get 9pt, newspaper size. 2.5 of that is is 11-12pt rounding. Now if you have 20/40 vision your critical print size at 16 in. is 9pt.  Double is 18pt and 2.5 times is 22pt. at 16in. Of course 20/160 requires 8 times that. That is hard to do even digitally, but 4 times at 1/2 distance is effectively 800%. 

??? Did you read this paragraph before sending? Didn't you say you were a mathematician? For a mathematician this paragraph is very unclear. Regardless not only do this and your other paragraphs have nothing to do with my post, it demonstrates a misunderstanding of several key concepts regarding research on reading speed which I hope to clarify below. BTW where did you get the numbers you're quoting? Because those are not from the cited Legge paper, nor are they in my post, and in any event they are not correct so I am assuming they are misreferenced.


LACK OF UNDERSTANDING
I suspect you don’t understand when acuity level is being referenced vs critical print size, because you are apparently confusing the two. You are also misunderstanding the nature of research stimulus sizes vs practical glyph sizes and font metrics. At any rate your math is using wrong values and wrong assumptions.

For the record, I was not using 16” as the stimulus distance in anything I mentioned in my post. That’s something I guess you saw in the Legge paper. Further the cited acuity figures you indicate are incorrect, as are the assumptions regarding increasing the stimulus size, as are your misconceptions of critical print size.

But to help us get on the same page, let’s start with stimulus distance. That paper was focused on reading, and mostly reviewed studies of reading printed materials (though some were indeed monitor based). 16” is a reasonable standard distance for a book or magazine, but not for a desktop monitor (22” to 40”), and not for a small mobile device (often as close as 4” to 5” to as far as 24”). 28” is a more useful monitor distance, and a more commonly used length. Since Acuity is based on visual angle, that means the physical font sizes will be different for the longer or shorter distance, etc. 

FWIW The measurement that's important in terms of research is visual angle. The visual angles that we are working with are essentially the same in the cited Legge paper and other research. But visual angle is what defines the CSS reference pixel:

 From W3C:
The CSS reference pixel is the visual angle of one pixel on a device with a pixel density of 96dpi and a distance from the reader of an arm’s length. For a nominal arm’s length of 28 inches, the visual angle is therefore about 0.0213 degrees. For reading at arm’s length, 1px thus corresponds to about 0.26 mm (1/96 inch).



PLAIN LANGUAGE
The outline I posted is up a work in progress for organizing some plain language ideas for functional needs, again, very rough. An idea behind plain language is to use only terms that are common knowledge. Visual angle is not plain language, but “20/20” in the US is fairly well understood as “normal” vision, as are the common font metrics like size. So the font sizes I mentioned are what people commonly know: the full point size, in CSS it is called font-size (in the old days of lead type, called the point body, also referred to as the type size, see left of below diagram).

 

RESEARCH IS DIFFERENT
“CSS font-size” is not what is used in reading speed research. The problem with using “font-size” for research as a way to measure fonts is that it is the entire font height from the top of the capitals to the bottom of a lower case descender, plus whatever built-in leading there may be. For vision research, we need a much more consistent and accurate measure, so we use a specific glyph, and one of the most common, and the one used in the cited Legge paper is called x-height. (See the right of the diagram)  

x-height is the height from the baseline to the top of the lower case x. x-height was mentioned prominently in that paper because nearly all the font measurements for nearly all the referenced experiments indicated size by x-height and not font-size. For Times, a print font used throughout much research including the cited paper, the x-height is 0.45 of the total font-size. The fonts more commonly used on a computers display such as Verdana, tend to have an x-height of about 0.55 of the total font-size.

Using Times as an example, this means that if the lower case x-height is 4.5 points, then the actual font-size is 10 points.


MATH IS FUN

5 arc-minutes is the letter-acuity level for 20/20 — that is the specified definition.

What this means in a practical sense is the entire height of the letter E subtends 5 arc minutes of visual angle.

When we are researching reading speed, we usually are using lowercase letters, then we use the lowercase x-height set to subtend five arc minutes of visual angle for the 20/20 letter acuity level as the baseline reference.

There are 60 arc-minutes in one degree, thus 5 arc-minutes equals 0.08333°
  MATH: 5/60 = 0.08333

At 16 inches, visual angle 0.08333° equals 0.02327” as the x-height.
  MATH simplified method, usable for small angles: (16 * 0.08333) / (180 / pi) 

0.02327” equals 1.68 points or 2.23 px for the 20/20 acuity limit x-height at 16” viewing distance.
  MATH: inches*72 = points or inches*96 = px

Times x-height 1.68 pt equals 3.7 point  font size (20/20 acuity limit)
Times x-height 2.23 px equals 5.0 px  font-size  (20/20 acuity limit)
  MATH: x-height / 0.45

ACUITY TO FONT SIZE CHART (BETA — 16” distance shown)



The "PT" section relates to font size by point, the "PX" section relates to font size by CSS pixels. 

The column under "PT" or"PX" is the x-height, which is at the acuity level (five arc min or 20/20). 


UNDERSTANDING STANDARDS

As a point of reference, the common standards for display minimum text size for readability in ANSI, FAA, and others relates to 22 arc minutes of visual angle. 

As established, the acuity limit is five arc-minutes.

Using our example of Times, a font size of 22 arc minutes would have an x-height of 10 arc minutes.

I don't think you have to be a mathematician to see that 10 arc minutes happens to be twice five arc minutes.

Twice. Well let's see what did that paper say a critical print size was? Oh yeah, two times or more.


ALREADY BUILT IN

You see Wayne, the paper you cited is not defining anything new. Classical design concepts have essentially used critical print size going back hundreds of years. And it's existed in the standards for a very long time. You seem to think that everything in the past has been based on minimum acuity size, but nothing could be farther from the truth. 

The font standards for displays, and for reading material, etc. are not based on minimum acuity–they're based on readability. In other words the essence of critical print size is already built in as a factor of good design.

And to dispel a final misunderstanding
In the chart above, you’ll notice that some numbers of font size are red — this is because you can't just keep increasing the font size to increase reading speed. At a point, text gets too large and reading speed once again will start to decrease. 

This goes back to what I've been saying for the last several months about how human perception needs fit within the range. And it also points to problems with severe impairments, in that while they may need to text to be made very large so they can discern it, the fact that it is made very large in itself interferes with their ability to read it quickly. This also points to problems where zooming in text to help one person actually can cause problems for someone with a different impairment.


> WAYNE: The sizes suggested in WHO report will definitely result in size induced slow reading and a serious error rate.


What WHO report? I’m not using it. The only reference in my post were the previous WHO categories, and I'm using the older categories because that's where it uses the term "low vision". The new categories for the same 20/70 - 20/200 level uses the term "moderate" I don't know about you but I think low vision works better as a more descriptive term for the general public. The term ”moderate” makes it seem less important, or less impairing. 

The original work we are doing right now in terms of critical reading speed related testing is ongoing, so I will not comment further on CFS. And in the post did I discuss “critical print size” anywhere? No I did not, so I really don’t know why you decided to rip into me about critical print size, which you have just demonstrated you misunderstand. I did discuss critical CONTRAST which is different. 


COMMUNICATION

In the future Wayne, when you want to rip some of my work apart (especially unfinished rough drafts), you might consider asking me first so that we make sure that we're on the same page, or at least so you understand the context, particularly in connection with what is clearly stated as a very rough draft. 

Whenever you have asked me questions in the past, I have given you a lengthy and in-depth response. When ever you asked what was going on a I've tried to read you in and keep you abreast of the status when I was able. 

So why is it that you seem to be interested in interfering, blocking, and disparaging my efforts and research? Because that has been your tone & attitude toward me since your very first post to me in April. Please stop. 



Regards, 

Andy






> On Sep 19, 2019, at 3:14 PM, Wayne Dick <wayneedick@gmail.com> wrote:
> 
> Hi Jim,
> 
> This information is out of date. The report may have been published recently, but the background research is old.
> 
> The critical print size is about 2 times to 2 and 1/2 times the acuity limit. [legge, Bigelow, "Does Print Size Matter"]. This is true for normal and low vision. This means that 20/50 requires about 250% enlargement. 2/60 requires 300% etc. for critical print size. If the person has central retina damage the magnification factor is greater. 
> 
> Here is the math. The normal acuity limit at 16 in. is around 4.5pt with really clean eye chart font. Double that an you get 9pt, newspaper size. 2.5 of that is is 11-12pt rounding. Now if you have 20/40 vision your critical print size at 16 in. is 9pt.  Double is 18pt and 2.5 times is 22pt. at 16in. Of course 20/160 requires 8 times that. That is hard to do even digitally, but 4 times at 1/2 distance is effectively 800%. 
> 
> The critical print size is the minimum size a person can read at optimum speed and error rate.  The sizes suggested in WHO report will definitely result in size induced slow reading and a serious error rate. These numbers look like the kind of pre-digital data that was used for 1.4.4. We need to stop that old data. When print was on paper, 200% was all anyone could achieve. A pamphlet enlarged to 400% would become a small encyclopedia. We can do lots better today with digital data in markup language. 
> 
> Best, Wayne
> 
> On Thu, Sep 19, 2019 at 12:51 PM Jim Allan <jimallan@tsbvi.edu <mailto:jimallan@tsbvi.edu>> wrote:
> This comes from the AG (WCAG) list. Passing along for consideration.
> 
> ---------- Forwarded message ---------
> From: Andrew Somers <notifications@github.com <mailto:notifications@github.com>>
> Date: Tue, Sep 17, 2019 at 9:08 PM
> Subject: Re: [w3c/wcag] Proposal for color and contrast (1.3.1, 1.4.1, 1.4.3., 1.4.6, 1.4.11) (WCAG 3.0) (#901)
> To: w3c/wcag <wcag@noreply.github.com <mailto:wcag@noreply.github.com>>
> Cc: Subscribed <subscribed@noreply.github.com <mailto:subscribed@noreply.github.com>>
> 
> <snip>
> A BRIEF ENCAPSULATION OF USER VISUAL NEEDS:
> 
> Visual Acuity deficits:
> 
> Acuity is essentially the ability to resolve a stimuli in the eye and perceive it in focus. “Blurryness” is the plain language way to describe poor acuity.
> 
> A _primary_way to assist visual acuity is corrective refraction (glasses/contacts) which is outside scope. In terms of display or design, and for all other things being equal, acuity is assisted by the appropriate _SIZE_which needs to be within a range (not too small but also not too big) for best perception. 
> Some causes of acuity loss, such as cataracts, require surgery to correct.
> Classification of Acuity can be divided into three broad groups:
> 20/10 thru 20/63: normal through near-normal. Existing standards tend to be built around this range, which relates to a font size of 12pt on the printed page. This serves as a “baseline” or foundation from which stronger accessibility needs can be defined. 20/30 is the lowest acuity for a private pilot, and 20/40 is the lowest for non-commercial drivers in most states.
> 20/70 thru 20/200: Low Vision, per the WHO definition. If a font at 100% size is good for 20/63, then if you double the size to 200% (24pt), you accomodate 20/150. To accomodate 20/200, then increase size to 275% (33pt).
> Above 20/200: Legally blind. 20/400 needs 550% larger size (66pt).
> Discuss size adjust (user) and design minimums. And accommodating user changes without breaking content, etc. (methods).
> Contrast Sensitivity deficits:
> 
> Contrast Sensitivity Function (CSF) can be impacted by poor acuity, by retinal disease such as AMD, retinal migrains, by degraded ocular media (cataract, etc), and by neurological problems (MS, neuropathy). VERY ROUGH (to be written):
> 
> CSF deficits caused due to poor acuity (blurry vision) is typically helped best by addressing the acuity issues when possible. 
> CSF is directly linked to spatial frequency (i.e. size), especially closer to threshold.
> Increasing stimulus size will increase perceived contrast (within a range).
> A key aspect of stimulus size is the stroke width of a font (i.e. font “weight”) — Increasing a font’s size increases perceived contrast, but largely due to the increase of stroke width as rendered to the screen. Stroke width is the aspect of a font that most closely follows Michelson Contrast (gratings).
> Aging ocular media (lens, cornea, vitreous) can affect contrast, but moreover these can cause problems with glare which reduces perceived contrast, while simultaneously being made worse as stimulus contrast increases.
> Intraocular glare reduces or obscures perceived contrast, but contrast perception is improved by _reducing the contrast _of what is being viewed. 
> Put another way, higher contrast objects cause more glare which reduces the “contrast legibility” versus lower contrast objects that cause less glare. The extreme example is headlights from an oncoming car at night.
> TBD Discuss: luminance contrast, threshold vs supra and critical contrast levels. Discuss design contrast. Discuss display luminance adjust (user). Discuss polarity.
> Contrast Sensitivity Function is typically measured with a Pelli-Robson style of chart, which measures the “just noticeable difference” or threshold of visibility.
> A Pelli-Robson score of 2 indicates “perfect normal vision contrast” which equates to a contrast of 1% (i.e. 1.01 to 1 )
> A score of 1.5 is a noticeable degrading of CSF, and equates to a contrast of 3% (i.e. 1.03 to 1)
> A score of 1 is a serious contrast impairment, and equates to a threshold contrast of 10% (1.1 to 1)
> These are a measure of the point where a stimuli becomes visible, which is useful in a clinical setting for detecting disease, but do not indicate the level of “critical contrast” where an item is “most readable.”
> Visual Field deficits:
> 
> Closely related/essentially part of contrast sensitivity impairments are those relating to visual field.
> 
> Central vision loss is a loss of vision in the fovea (central vision) forcing these users to learn to read using their peripheral vision.
> Peripheral blindness, or narrowing of the visual field (aka tunnel vision),
> Makes it harder to notice changes in content (i.e. a warning message) outside of the area the user is looking directly at.
> Color Vision deficits:
> 
> Color Vision Deficiency (protan, deutan, tritan CVD types) is primarily helped by ensuring there is enough luminance contrast between items (i.e. between text and a background, or between roadways on a map and geographic features on the map). 
> 
> Also, ensure that color is not used as the sole means of providing information (that is, don’t rely on “red” as a color that means “stop” — descriptive text of symbols are also needed to communicate meaning.)
> Protanopia (red deficient) may have problems with some monitor types (such as UHD/Rec2020) the red primary is close to the cut off for the green cone and is perceived much darker.. (need plain language for this)
> sRGB monitors are recommended for Protanopia as the red primary is within the green cone sensitivity. The protan will see this red a little darker, which should be considered in calculating contrast.
> The rare monochromats are also aided by luminance contrast, though may need to set the display to a monochrome mode, and have control over luminance and ambient illumination (such as for rod monochromacy).
> Cognitive/Neurological related Visual Deficits:
> 
> 62% of the brain is involved in visual processing. Over 20% of the brain is dedicated to visual processing, and of 42% processes visual in conjunction with other senses such as auditory and tactile. 
> 
> The other impairment types above are mostly associated with the eye itself, these are associated with processing the signals from the eye.
> Someone who had a stroke, and the stroke damaged some part of vision processing may have a problem with only that aspect of vision. For instance, if the motion detection part of the brain is damaged, they may see a car that is parked, but when the car moves it “disappears” in that the brain ignores it/it is nor “perceived” (“ visual neglect ”)
> With agnosia, the visual pathways and brain are capable of _seeing_objects or people, but cannot _recognize_them. 
> Cognitive impairments, brain damage (from stroke or other incident) can also cause some of the functional problems normally associated with ocular impairments, such as  blurred vision, field loss, light sensitivity, hallucinations, etc.
> Ocular migraines can directly interfere with vision by introducing “blockage” to vision, such as with ocular migraines auras, which can appear as zig zags in the vision, “seeing stars”, etc. 
> In Closing
> 
> Some of things you mention in your initial issue are fairly well understood, and in fact making their way into either SC extensions for 2.2, or new standards and guidelines for Silver. (One example is font weight, as those proposed SCs are already being created).
> 
> However, you make statements that are not supported by research, your codepen notwithstanding. Visual perception is not binary logic, so "absolute" statements don't really fly in a field where there are no absolutes. Human perception is far more complex than can be determined by some examples at maximum contrast.
> 
> I have listed references and footnotes to authoritative research supporting most of my posts in #695 <https://github.com/w3c/wcag/issues/695> and elsewhere, and I do suggest reading through those references to gain a better understanding of the underlying concepts. In particular you might want to read Legge's book Psychophysics of Vision.
> 
> And please keep in mind these standards are ultimately about the functional needs of a very wide swath of users & impairments. It is needs that should be considered, not so much the abstraction layer methods.
> 
> Regards,
> 
> Andy
> 
> Andrew Somers
> WAI Invited Expert
> Color Science Research
> Silver Task Force
> Low Vision Task Force
> 
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> -- 
> Jim Allan, Accessibility Coordinator
> Texas School for the Blind and Visually Impaired
> 1100 W. 45th St., Austin, Texas 78756
> voice 512.206.9315    fax: 512.206.9452 http://www.tsbvi.edu/ <http://www.tsbvi.edu/>
> "We shape our tools and thereafter our tools shape us." McLuhan, 1964