[IxDA Discuss] 'Transparent' Apple Devices

[Will Parker]

On May 16, 2007, at 6:57 AM, pauric wrote:

> Will: "it should be possible to distinguish between 'touch' and
> 'press' events based on the area covered by the fingertip."
>
> That leads in to the problem of calibration.  A fat fingered
> Neanderthal such as myself is going to have a smaller footprint
> spread compared to someone who looks after their fingers.

Actually, there are two different sensor issues, depending on whether  
the touch-screen uses capacitance or optical sensors.

For capacitance sensors, the thing being sensed is the 2D 'footprint'  
of the electrical field around the fingertip. I've seen some research  
(which I'll have to look up again) which shows that it's possible to  
use the characteristics of that electrical footprint to determine  
both the extent of the fingertip flesh and the distance of the finger  
bone from the sensor surface. Using changes in those two factors, the  
researchers were able to distinguish between 'touch' and 'press' events.

For optical sensors, you'd have to look for a two-stage event - a  
touch for a certain period of time, followed by a firmer press. Look  
for a plateau followed by a spike in area covered, in other words. I  
think that would be a trainable user behavior.

Capacitance-based touch screens are known quantities for engineers,  
so Apple probably used that solution, but Jeff Han (http://cs.nyu.edu/ 
~jhan/ftirtouch/) made some interesting but vague comments regarding  
future announcements by his team immediately after the iPhone demo,  
so we're left guessing.

> Here's a direct link to the sms demo which allows for tracking
> control.  I think if they currently had the ability to show the
> bubble in between placement and pressing of the finger they would
> have included it in the demo.
>
> http://images.apple.com/movies/us/apple/iphone/300/ 
> phone_sms_f_20070109.mov

That's not strictly a movie -- it's an informational animation. Tufte  
Representation Rules apply.  };->

I'll try to get time to review the real-life iPhone demo movies this  
evening and see if there are any visual or behavioral clues there.

> Thats not to say it isnt possible, I just think its impractical given
> the spread of input device characteristics (aka 'fingers')

I think a larger problem (albeit for a smaller audience) arises if  
the iPhone screen uses capacitance sensors. These can't respond to  
touch by inanimate objects, such as mouthsticks, stylii, or even  
gloved fingers, so there's a potential accessibility problem.

BTW, I'm keeping an eye out for a solution in this area for a blog- 
buddy of mine who must use a mouthstick, so if you have ideas along  
these lines, please respond _in a separate thread_ or directly to me.

> Will: "Because the key bubbles provide visual feedback, the user's
> attention is drawn to the keyboard area, which in turn informs and
> improves their fine motor control."
>
> http://www.flickr.com/photos/pauric/500837495/
>
> I had wondered about this, a counter argument is that placing the
> bubble over other keys, in this case the D appearing over both E & R,
> negates the value of this, what do you think?

There's a whole can of human-factors worms in that argument.

Do keyboard users (QWERTY or otherwise) use vertically-adjacent keys,  
horizontally-adjacent keys, or some other mix of visual cues to  
orient to the keyboard? Is there a significant difference between  
experienced and inexperienced user populations? Are there cultural  
differences in visual keyboard orientation factors between Hopi and  
Yoruba keyboarders?

Let's just not go there right now. Please. ;-)

> And to tie this back in to Dan's original comment.  Given the
> complexity of the design characteristics  highlighted by the
> subsequent comments, a rear panel input sensor seems a long, long,
> way off.

Oooooh, yes. I think the most relevant comment I've seen on that  
matter is that thumbs are much better suited to independent side-to- 
side and rotary motions than fingers, especially when the fingers are  
ALSO being used to grasp the object being manipulated.

But what if this principle were adapted to interactions with, say, on- 
screen UI along the vertical sides of a laptop screen? It's rare that  
people interact with a laptop while holding it in their hands, so the  
whole finger-vs-thumb argument drops away.

I for one would welcome the ability to, say, control screen  
brightness by caressing the edge of my PowerBook screen, but only if  
that were an _addition_ to the control methods, rather than the  
primary method.

- Will

Will Parker
wparker at ChannelingDesign.com

“I wish developing great products was as easy as writing a check. If  
that were the case, then Microsoft would have great products.” -  
Steve Jobs