The space between the plastic and glass layers of a resistive touch panel is filled with air, and the air has a different index of refraction than the other layers, which makes the light bend as it passes from one layer to another. This can create visible artifacts that can impact the display quality.

The air gap is especially a problem when you view the display under high ambient light conditions, such as outdoors in bright sunlight. The outside light passes through the top layer, then bends when it hits the air gap, and can then reflect between the glass and plastic layers before exiting out the front of the display again. This bouncing light can reduce the image's contrast, making the display look washed out and impossible to see.

But probably the biggest problem with resistive panels in consumers' eyes is that they can sense only one touch at a time. If you touch the panel in two places at once, the combined effect will produce one coordinate for the touch point, and that will be different from either of the two actual points. There are ways to create resistive panels that can sense multiple touches at one time, but these can be expensive and complex, such as creating a matrix of separate contact pads on one of the layers.

Projected capacitance

Fortunately, there's a better way. Many mobile devices now rely on a technology known as "projected capacitance," often referred to in the industry as "p-cap" or "pro-cap." According to various sources, resistive touch has rapidly lost market share to pro-cap and is forecast to continue to decline.