A digital camera uses an image sensor for capturing the information. To understand the image sensor in the simplest way, its function is equivalent to that of a film piece. When you press the shutter button on your DSLR, you are allowing the light to come into your camera and strike the image sensor to perform the image exposure. This is similar to the way in which an image is under the exposure onto a film piece that you could find in an old 35mm film camera.
What are CMOS and CCD?
There are commonly two kinds of image sensor that you can find in both point and shoot cameras as well as DSLR models, including: CCD and CMOS.
In an image sensor, there are some certain pixels that are used for collecting photons (energy packages of light). Then, the photodiode will convert these photons into an electrical charge which is turned into a digital value through analog to digital converter (AD converter). Through this converter, the camera will carry out the processing task on these values and create the final image.
For CCD (short for Charge Coupled Device) sensors, a circuitry around the sensor is used for converting pixel measurements continuously. CMOS (short for Complementary Metal Oxide Semiconductor) sensors operate in the different way in which pixel measurements will be converted simultaneously and the circuitry is right on the image sensor. Between the two above types, CMOS sensor is more commonly used because its speed is faster and you have to spend less to buy such a sensor.
Color Filter Array Sensors
This technology is commonly found in most DSLR cameras in the current market. A color filter array is positioned on the top of the image sensor to record the green, red as well as blue elements of the light that comes into the image sensor.
Therefore, every single pixel just can measure only one color, and the image sensor will base on the surrounding pixels to estimate the remaining two colors. The image quality can be a little bit affected, but you won’t be able to see this in the modern cameras which offer the high amount of resolution.
There are three basic colors that are the most sensitive to your eyes, including green, blue and red. Other colors have been created by a mixing of the basic colors. In the film photography, the various basic colors had the exposure on the equivalent chemical film layer. In the similar way, there are three layers in Foveon sensors in which each layer measures one basic color. The above three sensor layers have been combined to create a mosaic of square tiles to form an image. This technology is pretty new and currently, just Sigma applies this technology only.