Wednesday, July 16, 2008

Pushing Pixels

Kodak brings digital cameras into the 50-megapixel range.

By Duncan Graham-Rowe

Fifty megapixels: Kodak’s new 50-million-pixel camera sensor manages to squeeze more pixels onto an array while simultaneously increasing the speed and reducing the power consumption of the device. Credit: Kodak

Last week, Kodak launched the first ever 50-megapixel camera sensor. While such high resolution goes beyond the needs of most consumers, for professional photographers the new sensor will enable photographs to be taken at an unprecedented level of detail.

For example, in a picture taken of a field one-and-a-half miles across, the sensor would make it possible for a viewer to detect an object measuring just one foot across.

This sort of resolution is only really essential for and targeted at high-end professional photography, in which high-quality images often need to be blown up large. But it could also be useful for some other applications, such as aerial photography as used for services like Google Earth. "The ability to have more pixels lets the plane fly higher, so you don't need as many pictures," says Mike DeLuca, marketing manager for Kodak's Image Sensor Solutions, based in Rochester, NY.

The sensor, which produces an array of 8,176-by-6,132 pixels, further closes the gap between traditional film and digital photography. "We're really close to how film was operated," DeLuca says. "It's very close." Now, he says, it's just a matter of the photographer's personal preference.

Normally, the smaller you make a pixel, the poorer the quality, says Albert Theuwissen, a digital-imaging expert and founder of Harvest Imaging, based in Bree, Belgium. "That is true for consumer as well as professional devices." DeLuca claims that in the case of Kodak's breakout sensor, new pigments actually increase the color quality rendered by the sensor, while other mechanisms enable the pixels to be just as sensitive as larger ones--and yet they're processed faster than in previous designs. What's more, he claims that the new sensor uses less power than its predecessors. "Every solution or step that makes the sensor faster and less power hungry is a step forward," says Theuwissen.

Kodak already has a sensor on the market with a resolution of 39 million pixels. But to further increase the resolution, the company had to not only reduce the size of each pixel from 6.8 microns to 6 microns, but also radically change the way that these charged coupled device (CCD) sensors work, says DeLuca.

"It's relatively straightforward to make the pixels smaller," he says. But because these devices comprise much more than just light-detecting elements, DeLuca says, they can suffer drops in performance if everything inside them is not shrunken along with the pixels.

"Each pixel has multiple structures," he says. Some are designed to pass a charge from one pixel to the next, to enable the image to be read off the device. Other structures ensure that any excess charge produced by bright lighting conditions doesn't spill out into neighboring pixels.

Another challenge is to maintain the dynamic range of the sensor--that is, its ability to detect light and dark simultaneously. In the sensor, this is basically a signal-to-noise issue, says DeLuca. "When you make the pixel smaller, there is less signal you are able to capture, because physically there is less ability to store electrons in that pixel. If we don't do anything else, what we end up with is a smaller signal with the same noise profile." To counteract this, Kodak has had to improve the amplifier at the output of the device, which reduces the noise.