3 Types of Digital Camera Sensors

Digital cameras are many and varied, so for now we will examine the 3 types of digital camera sensors that are most commonly found. These 3 are: the CCD (Charge-Coupled Device), the Bayer Filter and the Foveon X3.

1. Charge-Coupled Device

In photography terms, a CCD acts in very much the same way as a film roll in traditional film cameras. When a picture is taken, the CCD is exposed to light, which causes it to gather an electrical charge which corresponds to the intensity of said light into a capacitor. A control circuit then forces these capacitors to move the charge into a charge amplifier, which turns the charge into a voltage. These voltages are then processed and reconstructed into an image viewable on a screen. The size of the CDD sensor is important in digital photography, as it affects image quality in conjunction with the amount of megapixels it supports. For a fixed amount of megapixels, a larger CCD allows bigger pixels, which improves light sensitivity and enables more freedom in controlling shutter speeds and aperture. Most high-end DSLRs today use CCDs.

2. Bayer Filter

In conjunction with CCDs, a Bayer filter is what gives digital images their color. The colors red, green and blue are laid out on a grid and placed on top of the CCD. It will only filter those three colors, from which all the other myriad colors are then defined by measuring the intensity of those three colors. But, why only three in the first place? This is because of human eye physiology, which dictates that it is most susceptible to the color green, hence when one looks at a Bayer filter, half of the pattern is only green, while both red and blue are only 1/4th of the whole filter. Now, each pixel gets only one color filtered in, so in addition to the processing of voltage into image as mentioned above, a demosaicing algorithm is used to properly process the colors of the image.

3. Foveon X3

A relatively new design, the Foveon X3 sensor, manufactured by Foveon Inc, is a direct image sensor, where each space on the grid is sensitive to all three primary colors, the red, green and blue, in contrast to the Bayer filter used by CCDs. The X3 refers to its three layers of pixels embedded in silicon, which exploits the fact that each of the primary colors penetrate silicon to different depths. The advantages of this new bit of technology are many. Each pixel is able to capture all three colors; the demosaicing algorithm is no longer needed to reconstruct a full-color image. This in turn eliminates the need for sharpening filters and anti-aliasing needed during the demosaicing. Another apparent advantage is an increase in image quality due to the fact that one of the pixel layers is wholly dedicated to the color green, which is the color the human eye is most sensitive to.

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