Size Does Matter - Camera Sensor Sizes

July 11, 2016

Size Does Matter - Camera Sensor Sizes


Full frame, Four Thirds, APS-C, 1-inch. These terms are regularly thrown around when discussing cameras, but what do they really mean? Sensor size is an important part of choosing a camera as it has a direct effect on the quality of the final image. We take a look at how sensor size affects your images and how it might influence your choice of camera.

What's a sensor? The imaging sensor is an integral part of a digital camera. Located inside the camera (at the focal plane where film used to sit), it is a device that coverts an optical image into an electronic signal. This sensor converts light into pixels, eventually to the digital image we see on our LCD screens and computers.

Not all pixels are equal... - In general terms, the larger the imaging sensor area, the better the image. This is especially true at high-ISO values. All things being equal, a 20 megapixel full frame sensor will perform better than a 20 megapixel 1-inch sensor. This, in part, is due to the pixel pitch, or relative size of the pixels on the sensor. A small sensor may hold the same number of pixels as a full frame sensor, however the pixels themselves are larger on the full frame sensor than on the smaller one. Larger pixels can capture more light, more accurately resulting in better quality images, as well as clearer images at higher ISO values.

Bigger sensors, bigger cameras - the desirability of larger sensors must be tempered with the practicalities of photographic design. Like many things, sensor size is a compromise between quality and portability. Simply put, a larger sensor needs a larger camera body. Lenses, in turn, need to be larger in order to effectively cover the larger sensor area. Take full frame cameras, for example. Until the Sony A7 series, full frame cameras were fairly large and bulky. While the Sony A7 has gone some way to making full frame cameras smaller and more portable, they still require large lenses to cover the full frame sensor area.

Advances in lens design and sensor technology means that smaller sensors often perform just as well as larger sensors in many circumstances. Take Micro Four Thirds for example. The popular Olympus and Panasonic cameras come in a range of styles and sizes, but they are all considerably smaller than standard DSLRs. Their smaller sensor size means that lenses do not have to be as large as their DSLR equivalents to cover the whole sensor area. While the smaller sensor does mean some compromises are made in image quality, particularly high-ISO performance, detail is surprisingly good for such a comparatively small sensor.

Taking a look at the DxO Mark test results below, what may seem at first glance an unfair comparison makes for very interesting reading. Considering the Nikon D810 retails for $3,695 and the GM1 for $749, the smaller camera puts up a good fight! For many purposes, the GM1 would be the preferred choice, considering its size and portability. Of course, such a camera doesn't replace a full frame 36 megapixel D810, but for many people it would suffice.

The NEW Compact Camera - A new sensor size has taken compact cameras by storm. The 1-inch sensor is smaller than DSLR sensors, but it is considerably larger than the very small 1/2.3" sensors used in most compact cameras. For many purposes, 1-inch is a "Goldilocks" sensor size that is small enough to fit in pocket cameras, but large enough to take high-quality images in low light. It is used in cameras such as the Nikon 1 series, the popular Sony RX100 III and the Canon Powershot G7 X. These cameras feature a range of enthusiast features such as full manual control and fast, large aperture lenses, but are comparatively small and lightweight. The downside to many of these cameras is compact camera-like operation speed, which is usually not up to DSLR standards.

The Choice Is Yours - So, if you're in the market for a new camera, what should you look at? For most people, choosing a camera is a compromise between size and portability. While we all full frame performance in a camera the size of a credit card, the laws of physics say it is not possible.

Full frame cameras offer the ultimate performance at the expense of size; both camera bodies and lenses.

APS-C cameras offer excellent performance in a size slightly smaller than full frame DSLRs.

Micro Four Thirds cameras offer good all-round performance in a compact size with considerably smaller lenses.

1-inch sensor compact cameras offer excellent image quality for their size, but are sometimes slower in operation than DSLR and mirrorless cameras.

This is a very basic overview, for more detailed information about pixel and sensor size, we recommend reading Roger N. Clark's article Does Pixel Size Matter?

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