Guide to CCD & CMOS Camcorder Image Sensors

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The sensor of a camcorder (as well as a digital camera) is defined as a component to bring the “digital” into a digital camcorder. To understand it in a simple way, the light captured by the image sensor in the camcorder’s lens and turned into a digital signal. This kind of light is processed and put into the storage space of the camcorder’s memory as a digital movie file that can be viewed later on TV sets or computers. The image sensor is located near the lens and it is an important component to measure the movie quality.

You often find two major kinds of camcorder image sensors, including CMOS (complementary metal oxide semiconductor) or CCD (charge coupled device). The number of pixels contained in these two kinds of sensors is up to hundreds of thousands or even millions. Imagine that each pixel is like an extremely small bucket for capturing the lighting and turning it into an electrical signal.

CMOS sensor

CMOS sensor

What are the differences between a CCD and a CMOS sensor?

In a sensor that uses the CCD technology, the light will be captures by pixels and moved toward the chip edge at which this light is turned into a digital signal. Meanwhile, the light coming into a CMOS image sensor will be converted right at the pixel – so there is no electrical conveyor with this kind of sensor. Here is the difference: as the light is directly converted at the pixel without needing any moving toward any edge of the chip, a smaller amount of power will be needed with an image sensor using the CMOS technology. Therefore, the battery life with a CMOS image sensor is longer than that of a CCD sensor. Obviously, nothing is absolute; do not think that the battery life with a camcorder using CMOS technology is always better than a CCD one.

The CCD had been the superior one in many years in the past regarding the concerns about the image as well as movie quality. However, recently, the CMOS technology has made significant innovation and become more and more popular in a larger number of camcorders at a wide variety of price points. For example, currently Sony is applying the CMOS technology for one of the high-end HD camcorders – it’s the HDR-XR520V.

Obviously, there are certain differences between the CCD and CMOS technology, but the average buyer does not pay much attention to these differences. You don’t need to pay too much attention to the sensor kind, but you should notice the number of pixels as well as the physical size of a sensor in a camcorder.

The Number of Pixels

In the specification list of a camcorder, there are often two image sensor parameters: the gross and the effective pixel counts. The first one involves in the total of pixels on the image sensor while the effective count refers to the number of pixels that shall be used for recording still images or videos. Therefore, you should care more about the number of effective pixels when checking the video resolution.

In addition, the number of effective pixels should be paid more attention to, because it will help you really know the resolution of a sensor, not through exaggerating marketing campaigns. Let me take an example with Camcorder A. This camcorder is introduced with the capability to shoot a 10-MP image (an image containing 10 million pixels). But the effective pixel count on the sensor is 4 MP. So how can 4-MP image sensor capture a 10-MP image? This processis known as interpolation. Commonly, the image quality of images produce with this process should be discounted before you can get the actual and meaningful pixels information. Therefore, the effective pixels count on the image sensor is the thing that you should consider when checking the actual resolution of your images.

How is the size of an image sensor important? 

The pixel counts on the camera sensor are not the only aspect to decide the quality of movies recorded. You should also pay attention to the physical size of an image sensor. A great amount of light will come into a sensor of a large size even when the number of pixels in this sensor is less. Although the number of pixels is less but because their sizes are larger, so they can take a larger amount of light.

It’s the reason why not only the pixel counts but the sensor sizes are also advertised (the size is measured in fractions of one inch). It is suggested that you should buy a camcorder with a larger sensor even with a smaller number of pixels, rather than the one with a smaller size of sensor and a larger number of pixels.

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