Tuesday, April 29, 2014
The heart of any digital capture system is the image sensor. Incredibly fast-paced improvements in resolution and performance have brought us to a point where the next quantum leap is on the horizon.
|This Article Features Photo Zoom|
Because each pixel records only one color of light, not all the photons falling on the sensor are used; just half of the green ones, and one-quarter of the red ones and blue ones can be recorded. By using wider-ranging (less specific) colored filters in the Bayer array, sensor manufacturers can allow more light to reach each pixel (at the cost of less precise color rendering); still, at least half of the green light and three-quarters of the red and blue light are lost.
The Bayer system also means that the sensor doesn't deliver as much resolution as its horizontal-by-vertical pixel count implies because not all the information coming from the lens is recorded at each pixel site.
We should state again that despite these drawbacks, Bayer sensors work very well; pro DSLRs and medium-format cameras have used them for years, with pro image quality. But the drawbacks are there.
As technology has advanced, microlens technology has improved to bring more imaging light to the photosites.
Now, Sigma has announced a new Foveon sensor, the Quattro. Like previous Foveon X3 sensors, the new X3 Quattro features vertical color separation technology rather than colored filters to derive color information. Like previous X3s, the new sensor stacks three pixel layers, the top one recording mainly blue, the middle one, green, and the bottom one, red wavelengths. Where previous X3 sensors had three layers of identical pixel count, the new Quattro features a 4:1:1 ratio—the top layer has four pixels for each pixel in the lower layers. This allowed Sigma to up the pixel count while reducing noise and speeding up processing and writing times, thanks to less total data per image file, all while retaining the essential Foveon assets—each primary color recorded at every pixel site, no moiré and no need for a blurring optical low-pass filter. A new TRUE III processor designed for the Quattro sensor optimizes image quality and speeds performance. (For the record, the 14-bit RAW files output by the new X3 Quattro sensor measure 5424x3616 pixels compared to 4704x3136 for the X3 Merrill sensor's 12-bit files.)
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