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Andrea Allen
February 17, 2011 by Andrea Allen PRO

If you're in the market to buy a new digital camera, you're probably going to read a lot about sensors. The more you know, the better equipped you'll be to make your camera purchase.

What is an image sensor?
An Image sensor is a device that converts the light from your lens to an electrical signal that's interpreted and displayed as an image.

Cool. How does it work?
Light travels through the lens of your camera and strikes the sensor. The sensor then converts that light information into electrical activity which is then interpreted by your camera's onboard computer and displayed as an image. This all requires loads of digital magic in a language that only your camera and memory card really understand. The image that your camera records will be made up of little squares of color called pixels which are the building blocks of every digital image.

Before the age of digital videos, the standard recording format was 35mm film in cameras. Now that we use digital formats for video it's become a little more complicated because there are many different sizes of sensors. Sensors that measure 36X24mm are called Full Frame sensors because they are basically the same size as that old 35mm film everyone used to use. Most mobile phones, point & shoot cameras, and even camcorders have significantly smaller image sensors than what is typically found in a DSLR. The diagram below shows the relative sizes of image sensors on cameras you are likely to encounter.

The bigger the sensor, the more light can be captured, which means you end up with more detailed images. Smaller sensors have less surface area so they don't pick up fine details or perform as well in low light.

Now, with all this information it might seem like the only camera for you is one with a full frame sensor, but that may not be the case! There are plenty of reasons cameras with smaller sensors would be good to buy. For one, they're usually much, much cheaper and smaller. If you're just shooting everyday video for fun the image sensor on your mobile phone, point & shoot camera, or camcorder should do just fine.


Erfan Al-Keilani

Great read! I learnt something new about image sensors thank you again for posting.

José Torres

Thank you for your article, it helps me understand what to look for when I buy my next photo camera.


Low end and High end DSLRs might not be the correct terms in describing sensor sizes. The 7D can be considered as a High end DSLR but it's got APS-C sensor.

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