- From: Gregg C Vanderheiden <greggvan@umd.edu>
- Date: Thu, 12 Jan 2017 16:28:05 -0500
- To: "Patrick H. Lauke" <redux@splintered.co.uk>
- Cc: GLWAI Guidelines WG org <w3c-wai-gl@w3.org>
Read my email, and WCAG glossary definitions. I THINK all your questions are answered there. Gregg C Vanderheiden greggvan@umd.edu > On Jan 11, 2017, at 12:25 PM, Patrick H. Lauke <redux@splintered.co.uk> wrote: > > On 11/01/2017 16:35, Gregg C Vanderheiden wrote: > >> I agree that rewording the animation SC to "1/3 of the viewport” >> rather than referring to web page is better. You will still need >> to make assumptions about screen size, resolution, and viewing >> distance. > > As physical (i'm assuming you mean physical?) screen size, pixel density (assuming that's what you mean by resolution, i.e. the dpi/dppx) and viewing distance are all variables that are essentially unknown/impossible to detect for authors, and impossible for testers to cater for all possible variations, I'm assuming it's ok to make those assumptions? > >> We started with the language direct from research. > > Likely the research had some standardised measurements etc that it was anchored on (a particular screen size, a user sitting X feet in front of the screen, etc)? In that case, the direct applicability of those measures to a fundamentally variable scenario of potentially infinite variations of physical screen size, viewing distance, etc is questionable I'd say. yes it did have standardized measures. No I don’t think it is questionable - because of the structure we used. if you start at a point and set a criterion that is safe where all the variability goes toward more safe views. the only thing not covered is if a person uses a magnifier on the flashing element. But that will fail no matter what you do and the author can’t predict or address that anyway. > >> We then >> translated it into language that were meaningful (pixels) (see Note >> 1) — but no matter what you translate it into - it is impossible to >> evaluate a screen manually and you must use a tool of some sort. So >> we made sure such a tool was available and free. [Note: since Trace >> moved from University of Wisconsin-Madison to University of Maryland, >> College Park the update on the tool broke. We are in the process of >> fixing that. ] > > Does the tool require you to enter the variables like physical screen size, viewing distance, etc? Or does it simply base its calculation on the screen/window size? If the latter, then it's doing nothing different from what I'm proposing, i.e. anchoring any measurement on viewport/screen size and writing out clearly what that ratio is.’ No, If you read the whole email I think you will see that this is covered. > >>>>> Does "visual field on the screen" not, in essence, mean the >>>>> full size of the screen/viewport? >> >> RE viewport — no "visual field on the screen” does not mean the >> same thing as Viewport since what the sentence says is "10 degree >> visual field on the screen” and so the visual field in that case >> in only a 10 degree visual angle portion of the viewport. > > So the answer is actually yes? i.e. "visual field on the screen" as a whole means the whole size of the viewport, and then of that you calculate a 10 degree angle portion? If so, then it is possible to rewrite the "10 degree visual field on the screen" into some relationship that's anchored on the size of the viewport? No - If you read it more carefully I think you will see why this is not true. at least not how it is used in the FLASH SC. > >>>>> And if not, isn't the general flash/red flash definition not >>>>> also fundamentally flawed as it can't take into account >>>>> physical screen size / viewing distance / etc, regardless of >>>>> the existence of a "tool"? >> >> Not flawed. But it is subject to the same problems you are talking >> about with this SC. If you read the rest of the text of the >> glossary definition you will see we addressed them by assuming screen >> size, resolution, and viewing distance. Since (in this case) we are >> talking about things being a problem if they are large— our >> assumptions were based on typical to older screens — with newer >> screens creating less of a problem. So viewing the material on a >> higher resolution screen or on a mobile device would alway be safer. > > But a mobile device screen is usually held closer to the viewer's eye, which in essence means that it occupies the same/similar overall visual field of a user as a larger monitor that's further away, no? While that is true — it is so much smaller that the distance difference is completely overwhelmed by the size difference — and the math still works out. it is safer— so criteria is still met. > >> So our criteria resulted were based on research, were set to >> accommodate most common and older tech at the time, and still held >> (were safer) with newer and mobile screens. > > I think this may need a rethink, or at least a different anchoring, to make it more generally relevant in a world where screens come in all shapes and sizes, resolutions, and typical viewing distances. The animation maybe - but the Photosensitive epilepsy provision still works even as we invent more shapes and sizes and resolutions of screens as long as we are viewing them at typical viewing distances for the different shapes sizes and resolutions > > P > -- > Patrick H. Lauke > > www.splintered.co.uk | https://github.com/patrickhlauke > http://flickr.com/photos/redux/ | http://redux.deviantart.com > twitter: @patrick_h_lauke | skype: patrick_h_lauke >
Received on Thursday, 12 January 2017 21:28:42 UTC