Touch screen target size

10 Oct 2005 - 3:00pm
8 years ago
3 replies
1884 reads
Norm Cox (sent ...
2005

It's been a while since I've designed a touch screen interface, so... given a 15" LCD display and finger for stylus, what's the general consensus for the size of a discreet target? In the olden days on a CRT, it was typically about 20mm or 3/4". Given the reduction in paralax, improvements in touchscreen technologies, and such, what is a "standard" target size?
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Comments

11 Oct 2005 - 8:34am
Elizabeth Buie
2004

Norm Cox writes:

> Given the reduction in paralax,
> improvements in touchscreen technologies, and such, what is a
> "standard" target size?

Norm, parallax and technology notwithstanding, I don't think that
fingers have gotten any smaller... :-)

3/4 inch is what ISO and ANSI prescribe, with 1/8 inch of separation.

Elizabeth
Norm Cox wrote:

11 Oct 2005 - 11:38am
Norm Cox (sent ...
2005

Elizabeth,

Thanks for your reply, and I certainly understand that fingers aren't getting any smaller. However, there are many products that we're expected to use with our fingers, and that have targets much smaller than the 3/4" per ISO and ANSI--e.g., cell phones, PDAs, calculators, watches, etc. While I understand that there are other factors to consider in the touch-ability of these hardware products, I'm trying to find out if there's any knowledge/research/correlation out there that considers our trend toward smaller touch-input devices and better touch-screen technologies (finer resolution, little/no paralax, etc). Have these recent "advancements" had any effect on standards?

I suspect that standards haven't changed, so I guess I'm looking for any recent evidence that a smaller touchscreen target sizes have been found to be acceptable.

Thanks, Norm

Elizabeth Buie-3 wrote:
>
> [Please voluntarily trim replies to include only relevant quoted material.]
>
> Norm, parallax and technology notwithstanding, I don't think that
> fingers have gotten any smaller... :-)
>
> 3/4 inch is what ISO and ANSI prescribe, with 1/8 inch of separation.
>
> Elizabeth
>
>
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12 Oct 2005 - 6:38am
Elizabeth Buie
2004

Norm Cox writes:

> However, there are many
> products that we're expected to use with our fingers, and
> that have targets much smaller than the 3/4" per ISO and
> ANSI--e.g., cell phones, PDAs, calculators, watches, etc.

I think that these are not particularly relevant to touch screens
because of the way that their buttons work and the unambiguity of when a
button has been pressed.

> While I understand that there are other factors to consider
> in the touch-ability of these hardware products, I'm trying
> to find out if there's any knowledge/research/correlation out
> there that considers our trend toward smaller touch-input
> devices and better touch-screen technologies (finer
> resolution, little/no paralax, etc).

I have recently come off a touchscreen project that used more modern
technology, and from that experience I would not go lower than the 3/4
inch required by ISO and ANSI.

> I suspect that standards haven't changed, so I guess I'm
> looking for any recent evidence that a smaller touchscreen
> target sizes have been found to be acceptable.

We did have a few buttons that were smaller than that (in height, not in
width), but the separation between those buttons and other touchable
objects was at least half an inch. We also made sure that nothing came
within 1/4 inch of the title bar (which we could not eliminate), in
response to users' complaints that they were accidentally hitting the
close box.

It's not so much a matter of parallax or resolution but of how to
determine which object the finger is touching. And of course on a
touchscreen one's finger can move a little and touch a nearby object,
while on a cell phone or PDA that's far less likely. (I restrain myself
from saying "impossible"; as soon as I did, someone would show me how it
was possible. :-)

Elizabeth

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