Re: Over 400%

Alastair,

Let's look back at what low vision is.  It is a person whose best corrected
vision in at least one eye can be 20/200.  Vision 10 times lower than 20/20.

As a person whose eyes are degrading (I'm 53)...my vision can still be
corrected to 20/20-ish.  I may be at 20/25.

I'm constantly magnifying by 150%...then 175% and have even found myself at
200%.  Some of this need for magnification is just older eyes too.

If we say 400% is the max, and if you need more than 400%...you should use
a screen reader, I think we are ignoring the reality of what low vision
users benefit from.

I've spoken to many experts over the years (including AT manufacturers)
asking this question, "At what level is magnification no longer effective?"
 The answer I get back (from people who had vision degrade and eventually
switched to screen readers) is...some where above 600% (because 600% is
still a valuable magnification option).

When I do usability testing with people with disabilities, this are the
parameters:

Screen Magnifier User (with visual acuity between 20/70 and 20/200) that
uses 4x to 6x magnification.


For usability testing, I don't go above 6x magnification, because I want to
focus on the 95% of that population (2 standard deviations in a bell
curve)...not the outliers.

G

glenda sims    |   team a11y lead   |    deque.com    |    512.963.3773


*web for everyone. web on everything.* -  w3 goals

On Thu, Jun 8, 2017 at 6:28 AM, Marla Runyan <marlarunyan1@gmail.com> wrote:

> I can certainly provide some additional information here on this topic.
> Will do so later this morning.
> Thank you, Alastair.
>
> Sent from Marla's iPhone 6 Plus
>
> On Jun 8, 2017, at 6:37 AM, Alastair Campbell <acampbell@nomensa.com>
> wrote:
>
> Hi everyone,
>
>
>
> David brought up a point on GitHub that warrants a response:
>
> https://github.com/w3c/wcag21/issues/58#issuecomment-306219839
>
>
>
> “My experience is that once we need more than 400% (4x zoom), we are
> really into screen reader territory.”
>
>
>
> Could someone speak to the advantage of having a linearization method at
> over 400% rather than using a screen reader?
>
>
>
> It isn’t something I have much personal experience with, so I think an
> response from someone here would be better.
>
>
>
> Cheers,
>
>
>
> - Alastair
>
>
>
> --
>
>
>
> www.nomensa.com / @alastc
>
>
>
>