Screen Test Analysis Pits Smartphones Against One Another: iPhone Wins

Apple's iPhone has been generating tons of demand ever since it was unveiled in 2007, and right from the start, consumers seemed to adore the touch screen. Unlike many phones before it, the iPhone uses a capacitive screen, which reacts instantly to finger presses without the need for a stylus. Right or wrong, the phone has been hailed as the touch screen king for years now, but MOTO Development Group decided that it was finally time to put the supposedly mighty panel to the test.

A simple DIY performance analysis between the iPhone, Google's Nexus One, Motorola's Droid and HTC's Droid Eris put each of the modern smart phones to the test, with the primary objective being to find out which screen was superior. Specifically, the goal was to create a technique so that "anyone could evaluate the resolution and accuracy of a touch screen device before they buy." (In other words, you too can do this test.)

To conduct the test, consumers open a basic drawing program and draw a few diagonal lines drawn across the screen. For the full explanation, just scroll down a bit. For those looking for the short version, the winner was indeed the iPhone. The reason? "The iPhone’s touch sensor showed the most linear tracking with the least amount of stair-stepping. The Droid Eris and Nexus One tied for second with only faint wiggling – but actually performed best at the edge of the screen. Last in the line-up was the Motorola Droid, which demonstrated significant wavy artifacts or "stair-stepping." We're guessing this will cause all sorts of controversy, but be our guest and post your own results below should you try to replicate it.

DIY with One Finger and a Drawing Program

MOTO Development Group created the simple technique so that anyone can evaluate the resolution and accuracy of touchscreen devices before they buy. To conduct the test, consumers open a basic drawing program and draw a few diagonal lines drawn across the screen.

Draw Slowly. On a quality touchscreen, people can draw clean straight lines, even while going very slowly. The image that appears on screen accurately represents the slowly drawn lines. However, on inferior touchscreens, it’s basically impossible to draw straight lines. Instead, the lines look jagged, stair-stepped or zig-zag, no matter how slowly you go. The inferior image results from the sensor size is too big, the touch-sampling rate is too low, and/or the algorithms that convert gestures into images are too non-linear to faithfully represent user inputs.

Pressure Matters. A good touchscreen device will produce linear output regardless of whether you're using the full pad of your finger, or just the edge. If you want to test the most extreme performance, draw very lightly with the edge of your finger. The artifacts will increase significantly, showing which device is really the best with a weak signal.

Even on a single device, the amount of pressure and the part of the finger you use on the screen has an impact on how well it senses. This is important because quick keyboard use and light flicks on the screen really push the limits of the touch panel's ability to sense.

A good touchscreen device will produce linear output regardless of whether you're using the full pad of your finger, or just the dry corner of your cuticle. When comparing devices, make sure to use even pressure across all of them.

Millimeters Matter.

Small differences in touchscreen sensitivity actually reveal exponential difference in performance. Less sensitive touchscreen systems are infuriating to use for typing.

DIY Touchscreen Analysis from MOTO Development Group on Vimeo.

The Real End Game

To create a superior touchscreen experience, the key is to develop a touchscreen sensor that has the highest possible signal-to-noise ratio, or SNR. When a manufacturer gets it right, the device tracks touch inputs almost as if they were connected to physical objects in the real world. Key drivers of SNR include:

  • Conductive sensor material
  • Substrate material
  • Substrate thickness
  • Distance from display (the biggest noise source)
  • Sensing waveform
  • Sensor pattern
  • Sensor pitch
  • Analog sensing circuitry
  • Sample rate

Touchscreens are a catalyst for innovation and a powerful way for device manufacturers to differentiate their products in an intensely competitive marketplace. But as MOTO’s demonstration shows, there’s a right way and a wrong way to deploy the technology. MOTO has worked with capacitive touch interfaces for more than 15 years, and offers up these essential dos and don’ts for anyone entering the field:

  • Don’t skimp on materials. With touchscreen hardware, manufacturers get what they pay for — and consumers will notice the difference.
  • Allow ample time to develop your algorithms. Don’t treat touchscreen algorithms as an element of component sourcing; create a distinct touch development track in-house to make sure your products are both responsive and accurate.
  • Closely integrate touchscreen hardware, software, and user interaction development as early as possible in the product development process. Never treat them as separate tasks.