How a Camera Sensor Works

A Single Lens Reflex or SLR camera enables us to see the exact image when taken on the film or a camera sensor beforehand through a viewfinder. An image of the taken picture will be reflected by a mirror to a pentaprism onto an eyepiece that we will see. When the camera trigger is pulled, the mirror will flip allowing light passing through onto the film or sensor, capturing the image.

In the past, video camera tubes were used as sensors. Today, we have replaced these tubes with either a CCD or CMOS.

The Difference Between a CCD and CMOS

A Charge-Coupled Device (CCD) is slow and requires more power. Information on the chip is read one pixel at a time to have full accuracy, therefore the processing time takes longer. CMOS or Complementary Metal Oxide Sensor is an active pixel sensor. It is cheaper than CCD. It is fast because it requires less power. CMOS converts photon and light signals into an electron, and to an electrical signal on the chip. As a result, this process is much faster than a CCD. Incoming lights with infrared and RGB (Red-Green-Blue) elements will go through an infrared-blocking filter before reaching the sensor. This is to block or reflect the infrared elements. The lights will then proceed to the color filter that controls the colors of the light before reaching the sensor. Lastly, the light will move onto the Color Blind Sensor that will convert all light that reaches the sensors into an electrical signal.

Bayer Sensor

A bayer sensor is the cheapest and the most used. It uses the Color Filter that filters RGB into pixel sensors. The Backside Illumination (BI) sensor is used too when light coming from the opposite direction reaches the sensitive silicon.  BI helps to increase the efficiency of the sensor, as some light may have scattered within the circuiting layer before reaching the image sensor.

Foveon X3 Sensor

This sensor uses a collection of pixel sensors layering, to separate light through the inherent wavelength-dependent absorption property of silicon, so that three color channels are sensed in every location.


A 3CCD sensor uses 3 discrete image sensors as it has a dichoric prism to separate the colors. It is considered the best quality, and as a result, it is the most expensive. A dichoric prism is a prism that reflects color lights, and is usually used more than one prism.

In a digital camera, before the light reaches the sensor, it is filtered with color filter to separate the light. The separated color will then be recorded as gray scale information. If you set your camera to RAW mode, a RAW file will be saved into the memory card. Each RAW file consists about 12 to 14-bit data. If you set your camera to JPEG mode, the RGB colors will be combine--in a form known as demosaicing. By combining all the colors, a whole image is transformed. The final image is then converted into jpeg format and saved onto the memory card.

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