Is capacitive touch screen all hype?
The launch of Apple iPhone three years back made the touch screen popular in the mobile phones. Long back, before Apple, Nokia had flirted with touch screens but did not get the same success as Apple. Some people attribute the success of iPhone, apart from itunes, to its capacitive touch screen and its ability to support multi-touch. Suddenly, all the phone manufacturers wanted to have touch screens but most of the vendors could only supply resistive touch screens which according to a few people did not offer the same user experience. So what is it about capacitive touch screen that makes it stand out? Before I share my views on this, I would first explain the two types of touch screens and the difference between the two:
Resistive Touch Screen 
Resistive touch screens are composed of two flexible sheets coated with a resistive material and separated by an air gap or microdots. When pressure is applied to the screen, by a finger or other objects, the sheets are brought into electrical contact which causes a switch closure and a command is registered. The figure (source: Screen Tek) on the left shows how does a resistive screen works. Examples of resistive touch screen phones are Nokia 5800 Samsung Omnia, etc.
Advantages:
- Cost effective and duarble
- Can work in all climate conditions and in any environment like the restaurants, hospitals, etc.
- Input can be made using a stylus or finger. However, stylus is better suited.
- Less sensitive to scratches as compared to capacitive screens
Disadvantages:
- Normally does not support multi-touch though Nokia has announced that on its handsets, multi-touch would be supported on both resistive and capacitive touch screens
- Recalibration might be required over time as resistive touch screens are known to drift over time. However, this is a simple process and can be performed by users by a simple dot mapping.
- While using fingers, slightly more pressure needs to be put on the screen
- Provides only 75% optical transparency which means that its clarity is lower than capacitive touch screen
Capacitive Touch Screen 
A capacitive touchscreen panel consists of an insulator such as glass, coated with a transparent conductor (mostly indium tin oxide). As the human body is also a conductor, touching the surface of the screen results in a distortion of the body’s electrostatic field, measurable as a change in capacitance. Unlike its resistive counterpart, capacitive touch screens must be touched by a human finger or some sort of conductive device being held by a human hand. The figure on the right from Electronic Design shows how does capacitive screens work. Examples of devices with capacitive touchscreens are the Apple iPhone and the T-Mobile G1. Advantages:
- Higher clarity display (up to 90% optical transparency)
- Supports multi-touch
- High touch resolution
- High sensitivity
Disadvantages:
- Needs a human finger to register input. It is not possible to use this screen wearing gloves
- Cannot be used in all weather scenarios
Which touch screen is better?
Due to the success of iPhone, there is a common perception that capacitive touch screens are better suited for cell phones than the resistive touch screens. However, I believe that it does not matter whether the mobile phone has a capacitive screen or resistive screen – what matters is the software behind it. The operating system defines the user experience and if the operating system is not optimized for touch screen, even the capacitive touch screen would not enhance the user experience.
Do you agree with me? I am eager to hear your views on the issue.
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That’s an interesting point you made. While I agree with the overall message, I think there are 2 critical points which device makers will do well to take a note of while choosing a panel type:
1. Instant gratification: one of the most imp reasons why capacitive panels are gaining rapid popularity amongst users. With more and more focus on the s/w, users expect quick response from the display the moment the gesture is made. Even in some of the best resistive panels, I’ve observed that the latency is way too high as opposed to the capacitive displays. Accuracy of the touch is also an issue.
2. the Apple benchmark: the advent of the iPhone and its amazingly responsive capacitive panel has raised the bar of touch-screen displays really high – anything short of that will really fall flat on its face. Nokia has learnt this lesson the harder way and I think the N900 is really a step in the right direction.
What’s more surprising is the fact that not many industry folks saw the capacitive displays arriving. I remember doing some research around the displays – IDC forecasts drew a pretty dismal picture for the capacitive display panels just 12 months ago.
Overall, my sense is that capacitive displays are the future as far as consumer user cases are concerned. Sure, resistive varieties will continue to be deployed in industry verticals, but I won’t be surprised if that is showing a downward trend.
Right.. Abhishek.
The primitive resistive screens are not that responsive as capacitive screens. Also resistive screens do not offer multitouch capabilities (to date). The touch error rate is very high on resistive screens. So users get frustrated to see that actions is not done even after touching the screen. You must have see this if you have a phone with resistive screen. You will never see this in capacitive screens.
Chief Researcher , R&D Labs
Seoul, korea.