Understanding Sensor Sizes

In the last article I discussed megapixels. Your camera operates by using a digital sensor to capture light. Each pixel senses light and sends the information that it senses to the camera for it to be processed into an image. Essentially each pixel captures 3 black and white channels, one red, one green, one blue and the brightness of each. This information is relayed to the processor of the camera as a digital string of numbers. The processor then deciphers the data and produces a color image. This is the basic premise of an extremely complicated process but I think that it’s enough information to understand the topic of the day: sensors.


As you can see in the photo there are many different sensor sizes used in the digital camera world. The smallest box is close to the size of an iPhone sensor while the “Full Frame” box is most closely related to traditional 35mm film. This is where understanding megapixels and how pixels work comes into play. Regardless of how large or small your sensor is X megapixels is X megapixels.

Since the iPhone is 12 megapixels and also the smallest sensor on our list we will use 12 megapixels as the reference point. 12 megapixels on the smallest sensor will give you very small pixels. In order to fit 12 million pixels on a chip that tiny, the pixels have to be small. As you go up in size and get a larger sensor the pixels can be larger on the sensor. What’s the benefit of larger pixels? Light sensitivity. A larger pixel will be able to detect light more accurately than a smaller pixel thus giving better image quality all around and especially in low light. Since capturing light is what photography is all about I’d say that larger pixels should be a priority.

This is also why I mentioned megapixels not being everything in the article about megapixels. 12 megapixels on a small sensor are not equivalent to 12 megapixels on a large sensor. It may seem like the same thing, and you’re effectively getting the same number of pixels but the quality and the performance of those pixels will be very different. This is also one reason why large prints made from photos that were taken with cell phones often look atrocious. Optics also plays a major role in this but that is a topic for another day.

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