Two main types of sensors are used in digital SLRs today: CCD (charge coupled device) and CMOS (complementary metal-oxide semiconductor) imagers. Although each type of sensor uses different technology to capture images, there’s no inherent quality difference between them. Some vendors, including Sony, Pentax/Samsung, and Nikon, make great dSLRs based on CCDtechnology. Fujifilm’s latest dSLR uses what it describes as a SuperCCD sensor. But Nikon also offers dSLRs built around CMOS sensors (fabricated by Sony), so it’s logical to expect Sony to blossom into the CMOS arena, too. Firmly in the CMOS camp are Canon and Sigma. Note that although the Foveon sensor used in Sigma cameras is.

Both CCD and CMOS imagers use metal-oxide semiconductors (although,apparently, the CMOS type is more complementary), and they have about the same degree of sensitivity to light. The main difference is in what each type sensor does with the light after capturing it:

  • The CCD sensor
    is “dumb” to the extent that all it does is capture photons as electrical charges in each photosite/pixel. After exposure, the charges are swept off the chip to an amplifier located in one corner of the sensor. External circuitry converts the analog signal to digital form and handles storing it on your memory card.
  • A CMOS sensor,
    theoretically, is a lot more complicated than its CCD counterpart. It includes solid-state circuitry at each and every photosite and can manipulate the data for each pixel right in the sensor. That’s pretty cool because it gives the CMOS sensor the ability to respond to lighting conditions in ways that a CCD can’t. However, sweeping all the photon information off a CMOS chip isn’t necessary; every photosite can be accessed individually.

Some interesting components are piled on top of both sensor types. These components include

  • Color filters, which give the color-blind CCD and CMOS chips the ability to respond to various colors of light.
  • Teensy microlenses that focus the incoming light onto the photosensitive area in each photo site.
  • A protective transparent layer that contains a special filter (an antialiasing filter) that smooths out the incoming light signal by eliminating certain frequencies of light before they can clash. This layer also includes an infrared cutoff filter that removes most of the IR light component from the illumination reaching the sensor (because so-called “IRcontamination” can affect image quality and produce off-color colors).

No related posts.

Related posts brought to you by Yet Another Related Posts Plugin.

Tagged with: • • • • • • •

Filed under: DSLR Articles

Like this post? Subscribe to my RSS feed and get loads more!