Sensor sizes explained: what you need to know

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It used to be the case that if you bought a compact camera you’d have a small sensor, and if you went for an interchangeable-lens camera like a DSLR you got a much larger one. This would also typically be reflected in the quality of the images from those cameras, with larger sensors typically producing higher-quality results than smaller ones.

To some extent this is still the case. Sensors are typically the most expensive part of a camera to manufacture, and the larger you go the pricier the camera gets. For this reason you won't find expensive models toting 1/2.3-inch sensors, just as you wouldn't find cheap, basic compact cameras with full-frame ones.

Sensors are typically the most expensive part of a camera to manufacture, and the larger you go the pricier the camera gets.

However, as manufacturers started offering compact cameras with relatively large sensors, and interchangeable-lens cameras with smaller ones, the situation become more complex. Today, we find some small sensors work very well in a range of conditions, while some larger ones may present a handful of benefits over smaller ones in one way, but fall down in another. 

Sensor technology has advanced rapidly over the past few years, and the breadth of options across all kinds of cameras is likely to confuse many users, particularly first-time buyers who may not be sure what to expect from different kinds of sensors. Furthermore, as the size of sensor has a bearing on the effective focal length of your lens, this becomes yet another thing to consider when choosing a new camera. 

Here, we list the different types of sensor sizes used in cameras today, in ascending order of size, and how each affects image quality. But before we do that, we need to briefly talk about the relationship between sensor size and focal length.

Sensor size and focal length

The size of the sensor inside a camera has a direct effect on what kind of lenses can be used with that camera. 

If you buy a compact camera the lens is built into the body, so there's less to think about here from a buying perspective. But with interchangeable-lens cameras like DSLRs and mirrorless cameras, any lens used needs to be able to have an image circle – the diameter of the light that exits the lens – that can sufficiently cover the dimensions of the sensor. 

Whether they're built into the body of a camera or supplied separately, lenses are marked with their actual focal length, rather than the effective focal length when used on a particular camera. The problem here is that different lenses marked with two completely different focal lengths may provide the same effective focal range to work with when used on the bodies for which they are designed. To make things easier to understand, manufacturers often provide an ‘equivalent’ focal length, which uses the full-frame sensor as its reference point. 

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A 18-55mm lens used on a camera with an APS-C sensor has an effective focal range of 27-82mm, although the exact length depends on the camera used. Image Credit: Nikon/TechRadar.

Here’s an example. A camera with a sensor that’s smaller than full-frame may be used with a lens that has a focal length of 18-55mm, but in reality the effective focal range you’ll end up with is closer to 27-82mm. This is because the sensor is not large enough to take advantage of the lens to the same extent as a full-frame sensor can. By discarding some of the peripheral areas of the lens, it ends up appearing as though you’re using a longer focal length.

Similarly, a compact camera may have a 19mm lens built into it, but if the size of sensor is smaller than full-frame, it will only ever be able to offer a longer effective focal length on that body, perhaps 28mm or so. This figure is determined by the ‘crop factor’ – that is, the number by which you need to multiply the focal length to work out the effective focal length of the combination. This will be examined in greater detail for some of the sensor sizes below.

Sensor sizes

Here, we take a closer look at the main sizes of sensor used in today’s cameras. 

Note: not all sensors within the same category have exactly the same dimensions. The measurements provided are an example of one such sensor within that format.

1/2.3-inch

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Canon PowerShot SX70 HS. Image Credit: Canon/TechRadar. 

Dimensions: approx. 6.3 x 4.7mm

This is the smallest sensor that's commonly used in cameras today, and is typically found in budget compacts. They usually offer between 16-24MP. 

These used to be common across these types of cameras, but the gradual shift in focus by manufacturers towards enthusiast cameras with larger sensors means they aren't as common in new cameras. 

Their size allows manufacturers to make very compact cameras with long lenses, such as superzoom compacts like the Panasonic ZS70 / TZ90 and Canon PowerShot SX730 HS. They're also found inside DSLR-style superzoom compacts such as the Canon PowerShot SX70 HS. Using a larger sensor in such cameras would necessitate a larger, heavier and more expensive lens. 

For general snapshots taken in good lighting conditions, cameras using these sensors may deliver perfectly acceptable results, but otherwise they can struggle to hold on to highlight detail and may produce images with a grainy, noisy texture.

1/1.7-inch

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Pentax QS1. Image Credit: Ricoh/TechRadar.

Dimensions: approx. 7.6 x 5.7mm

Slightly larger than the 1/2.3-inch types above, these sensors make it a little easier to separate a subject from its background, and typically offer better performance with regards to holding onto detail in shadow and highlights. As they can capture more light than smaller sensor, they're also likely to perform better in low light.

These were once the default choice for enthusiast compact cameras, but their popularity has waned in the face of larger and more advanced 1-inch sensors (discussed below). Some of the most recent cameras to use these include the Pentax QS1, which was announced five years ago.

1-inch

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Sony RX100. Image Credit: Sony/TechRadar.

Dimensions: approx. 13.2mm x 8.8mm

This type of sensor is currently a popular choice across a range of compact cameras, with its size making it a versatile but high-performing option.

It’s most commonly used in pocket-friendly enthusiast compact cameras. Lenses on these cameras will typically be limited to around 24-70mm or 24-100mm (in 35mm equivalent terms), such as on the Panasonic LX15, Canon PowerShot G9 X Mark II and Sony RX100 VI. It has, however, also now featured in a handful of superzoom cameras from both companies too, like the Panasonic FZ1000 II and TZ200, as well as the Sony RX10 IV. 

Cameras that use these sensors can typically provide very good quality images, particularly as many of the compact cameras that use them have wide maximum apertures that let in plenty of light. This enhanced image quality is partly the result of their size, but also on the technology on which they're based. Recent versions may be built with an unconventional construction, for example, which enables them to capture light more effectively than standard sensors.

• Photography basics: angle of view

Four Thirds

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Panasonic GH5S. Image Credit: Panasonic/TechRadar. 

Dimensions: approx. 17.3 x 13mm

This is the format used by Olympus and Panasonic for its Micro Four Thirds mirrorless cameras, such as the Olympus OM-D E-M1X and the Panasonic GH5S.

These are a fair bit larger than the 1-inch sensors described on the previous page, but still smaller than APS-C types described below.

As this type of sensor has a surface area that’s around a quarter of the size of full-frame sensors, calculating the effective focal length of compatible lenses is easy: you simply double it.

So, a 17mm lens used on such a camera will provide an effective focal length similar to a 34mm lens on a full-frame body. Similarly, a 12-35mm lens provides a focal range equivalent to 24-70mm lens on the same camera.

A 17MP version of this sensor was also used by Panasonic in its recent Lumix LX100 II compact camera. Here this was paired with a lens that gave a focal length equivalent to 24-75mm on a full-frame camera.

APS-C

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Canon EOS M50. Image Credit: Canon/TechRadar. 

Dimensions: approx. 23.5mm x 15.6mm

Long used in entry-level and mid-range DSLRs, and now in many mirrorless cameras too, this type of sensor provides a good balance between system portability, image quality, and flexibility with regards to lenses.

Not all APS-C sensors are equal in size, however. Canon’s APS-C sensors, such as those used inside its EOS Rebel T7i / EOS 800D and EOS M50 models, are a touch smaller than those inside the Nikon D5600 and Sony A6400, and other models from those two manufacturers. Canon's APS-C sensor apply a crop factor of 1.6x rather than the 1.5x seen elsewhere. 

In any case, these cameras are still a good all-round, versatile option, and models that use them are often preferred over full-frame models by some nature and sports photographers, as the crop factor enables them to get closer to their subjects with a given lens.

APS-C sensors have also been employed in a number of compact cameras, such as the Ricoh GR III and Fujifilm's XF10 and X100F models. Here, in order to keep image quality high and the camera portable, they're paired with fixed focal length lenses. 

The Ricoh GR III, for example, has a 19mm lens, while the Fujifilm X100F has a 23mm lens and the XF10 has an 18.5mm lens. These provide focal lengths equivalent to 28mm, 35mm and 28mm respectively. These lenses also have fairly wide maximum apertures, which allows the user to more easily capture a shallow depth of field.

APS-H

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Sigma sd Quattro H. Image Credit: Sigma/TechRadar. 

Dimensions: approx. 26.6 x 17.9mm

This type of sensor was commonly associated with Canon’s older EOS-1D models, such as the EOS-1D Mark III and EOS 1D Mark IV, although the company appears to have moved away from the format, adopting a full-frame alternative for its current EOS-1D X Mark II.

Being smaller than full frame but larger than APS-C sensors, the crop factor of these is accordingly between the two at 1.3x. So, a 24mm lens used with such a sensor would provide an effective focal length closer to 31mm.

More recently, a 51MP version of this type of sensor was employed in Sigma’s sd Quattro H model. Canon also announced that it was developing 120MP and 250MP APS-H sensors within the last few years, although it stated that the likely applications for these would be for surveillance, crime prevention tools and industrial equipment among other things, rather than for commercially available DSLRs.

Full frame

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Nikon Z7. Image Credit: Nikon/TechRadar. 

Dimensions: approx 36 x 24mm

Full-frame sensors are used in many enthusiast and professional cameras, including the flagship DSLR and mirrorless models in many manufacturers’ lines. 

Their relatively large surface area allows them to collect plenty of light, which in turn helps to produce high-quality images, while the larger area gives the manufacturer more space to play with when it comes to deciding on the number of pixels. Currently, some have as few as 12MP, while others have 24MP, 36MP and even 51MP.

Full-frame sensors are (roughly) the same size as a 35mm film negative, so there's no crop factor to think about here. If you use a lens designed for a 35mm film camera on a digital body with a full-frame sensor, the effective focal length will be the same.

Depending on the system and manufacturer, some lenses designed for APS-C cameras can be used on full-frame bodies at a reduced resolution. Here, the camera essentially crops away the edges of the frame so that you don't get any darkening of the corners. You should, however, always check that your camera supports this, as using incompatible lenses can damage the mirror.

Popular current models that sport full-frame sensors include the Nikon Z7, Sony A7 III and Canon EOS RP mirrorless cameras. Panasonic has also started to use this format for its first two S series cameras, the S1 and S1R. Many DSLRs also continue to make use of these sensors, such as the Canon EOS 6D Mark II, Nikon D850 and Pentax K-1 II.

Medium format

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Fujifilm GFX 50R. Image Credit: Fujifilm/TechRadar. 

Dimensions: approx 44mm x 33mm

Medium-format sensors are significantly larger than full-frame types, and the arrival of a number of recent cameras using them has sparked a huge amount of interest in the format. These include the Fujifilm GFX 50R and Hasselblad X1D, and the slightly older Pentax 645Z.

Theoretically, medium-format systems allow for a higher standard of image quality than cameras with smaller sensors, mainly because they capture a lot more light that goes on to make up the image. A larger sensor can also make it easier for manufacturers to fit more pixels on the surface; Fujifilm is currently promising a 100MP medium format camera, for example.

Their practicalities and cost, however, largely confine them to professional use. DSLRs are typically easier to handle, for example, offer a much wider choice of native lenses, and can also autofocus much faster. 

If, however, we’re to base our expectations for the format on recent developments, we’ll no doubt see these sensors appearing in more affordable and compact bodies, along with improvements to performance and greater lens ranges.

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