Re: notes on 320 CSS Pixels to inches

And this specific discussion is why I have such a hard time understanding why we don't define the user's perceived physical, on screen size of the button as the minimum in the SC.  The majority of the research (and I've spent the past few days looking at over 500 pages of research studies on touch and target size) describe the stimulus used as the target in millimeters (aids replicability of research).  The human engineering design guidelines used in aerospace or the accessibility design guidelines for elevator controls define button size as a physical measure.  These are precise and meet the needs of the user.  When we talk about CSS Pixels, and define minimum target size in terms of pixels in a world of many display sizes and true pixel densities, there appears to be a broad acceptance that, yes, there is a fudge factor... the true measured size will vary, and that's okay.  I tested a number of devices and saw that variability.    Does that serve the user?   That the concept of CSS Pixels is hard to describe (as has been noted in many places), makes this SC problematic without also stating clearly the physical, measure on-screen physical minimum in an international unit of measure (mm).

On 1/18/18, 5:33 AM, "Patrick H. Lauke" <redux@splintered.co.uk> wrote:

    On 18/01/2018 05:12, Gregg Vanderheiden GPII wrote:
    > *Can someone check the thinking - calculations here? *
    > *thx*
    > *Gregg*
    >
    > *
    > *
    > *RE 320 pixels*
    >
    >     A CSS pixel is .26 mm

    I'll stop you right there to point out that on screen devices,
    everything is anchored on the ideal pixel. So when you start talking
    about converting CSS px to a measurement like mm, inch, etc, that still
    doesn't actually mean "as measured on the screen with a ruler", as
    devices/browsers do not actually know/care what the actual physical size
    of their display is.

    >       x 320 CSS pixels = 83.2 mm  = 8.32 CM = 3.275591 inch

    Case in point: most mobile phones, in portrait orientation, have a width
    of 320 CSS px. Now, there are a large variety of phones out there with
    varying actual physical dimensions...but they all have the same CSS
    pixel width. Take an actual ruler, measure the actual width of your
    phone's screen...and you're likely never to hit that exact measure in
    mm/cm/inches.

    > *RE 40 CSS Pixels *
    >
    >     and 40 CSS pixels would be  10mm or 1 CM
    >
    >     that would be a HUGE button on a phone

    Even assuming that this was always an actual 1cm as measured on screen
    (but as pointed out above, the actual dimension really varies), look at
    the actual size of a fingertip. Look at the area it covers when you tap
    somewhere. Look at the area it obscures while on a screen. While yes,
    the active "tip" of a finger can - with a lot of dexterity and control -
    touch a relatively small area, it gets tricky. Particularly if you then
    add any further factors like tremors or similar.

    >     and it would be hard to put many of those on a screen -  or much
    >     content on the screen with many links / buttons

    Which is why, if you look at native apps on mobile for instance, you'll
    notice that indeed they usually don't feature such a high density of
    controls as traditional mouse-driven interfaces.

    P
    --
    Patrick H. Lauke

    https://na01.safelinks.protection.outlook.com/?url=www.splintered.co.uk&data=02%7C01%7Cmhakkinen%40ets.org%7C852beeb1e1644c87d58108d55e5ee268%7C0ba6e9b760b34fae92f37e6ddd9e9b65%7C0%7C0%7C636518683982846994&sdata=%2FGPkLn%2BkxDXo34HB50If6gwucro7Rc4QtLtadw7O1bQ%3D&reserved=0 | https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fpatrickhlauke&data=02%7C01%7Cmhakkinen%40ets.org%7C852beeb1e1644c87d58108d55e5ee268%7C0ba6e9b760b34fae92f37e6ddd9e9b65%7C0%7C0%7C636518683982846994&sdata=n%2FnYZYoQ3S2%2FX%2FDTnPDS2a5qcqkXWaVIGjad6fl5EOo%3D&reserved=0

    https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fflickr.com%2Fphotos%2Fredux%2F&data=02%7C01%7Cmhakkinen%40ets.org%7C852beeb1e1644c87d58108d55e5ee268%7C0ba6e9b760b34fae92f37e6ddd9e9b65%7C0%7C0%7C636518683982846994&sdata=BaaOMx%2FfcaDfSYyccjzmtBSQavkOvhQaVgjAt3Ws6DA%3D&reserved=0 | https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fredux.deviantart.com&data=02%7C01%7Cmhakkinen%40ets.org%7C852beeb1e1644c87d58108d55e5ee268%7C0ba6e9b760b34fae92f37e6ddd9e9b65%7C0%7C0%7C636518683982846994&sdata=D58blesCvMwE6scpReUO%2FGwz889p4jJw5mfvN3%2BUTrA%3D&reserved=0

    twitter: @patrick_h_lauke | skype: patrick_h_lauke




________________________________

This e-mail and any files transmitted with it may contain privileged or confidential information. It is solely for use by the individual for whom it is intended, even if addressed incorrectly. If you received this e-mail in error, please notify the sender; do not disclose, copy, distribute, or take any action in reliance on the contents of this information; and delete it from your system. Any other use of this e-mail is prohibited.


Thank you for your compliance.

________________________________

Received on Thursday, 18 January 2018 14:45:12 UTC