- From: Patrick H. Lauke <redux@splintered.co.uk>
- Date: Wed, 11 Jan 2017 17:25:35 +0000
- To: GLWAI Guidelines WG org <w3c-wai-gl@w3.org>
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. > 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. >>>> 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? >>>> 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? > 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. 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 Wednesday, 11 January 2017 17:26:04 UTC