A camera’s sensor is the element that records light to create a photo when you press the shutter button on your camera.
Whether it’s a smartphone, a compact, a hybrid or an SLR, all digital cameras have a sensor. But depending on the devices, the size of this sensor is different.
The size of your camera’s sensor affects the photos you take. It influences the quality of the images, but also the size of the optics that will fit on your box as well as the size of the system as a whole.
In this article, I’ll explain how the size of your camera’s sensor can affect the photos you take.
The main sensors on the market
In the camera market, there are dozens of sensors of different sizes. We are going to focus today on the 3 types of sensors that equip the majority of reflex / hybrid type cameras:
“Full frame” type sensors — or 24×36 sensors
Full-frame sensors are so called because they replicate the dimensions of 35mm film, which were the most commonly used films in the era of analog photography.
These sensors measure 24mm in height and 36mm in width.
As with televisions, a very simple way to compare the size of the sensors is to measure their diagonal. Full-frame sensors have a diagonal of 43mm .
These are the largest sensors that equip the most commonly sold digital cameras on the market.
There are larger sensors, but their use is reserved for very specific areas of photography. I will therefore not talk about it in this article but know that it exists.
Full-frame sensors equip high-end cameras, whether they are reflex or hybrid cameras.
APS-C type sensors
APS-C type sensors are a bit smaller than full frame sensors.
They measure 15.5mm × 23.6mm which gives a diagonal of 28mm .
The APS-C sensors produced by the Canon brand are slightly different. They measure 14.8mm × 22.2mm which gives a diagonal of 27mm. The difference between these two sensors is so small that they will be considered identical.
Micro 4/3 sensors
The last type of sensor commonly found on the market is the Micro 4/3 format.
These sensors measure 13mm x 17.3mm which gives a diagonal of 22mm .
The smaller sensors
There are many types of sensors smaller than the micro 4/3 format. These sensors are generally fitted to compact cameras or smartphones. Due to their small size, they make it possible to create more compact cameras, but the quality of the photos is much lower than those obtained by larger sensors, especially when there is little light — I will come back to this later in this article. For simplicity, I will therefore not talk about these sensors today, but as for very large sensors, know that they exist.
Full Frame, APS-C and Micro 4/3 sensors are the most common sensors in cameras for amateur and pro photographers, but they are not the only ones that exist.
The influence of sensor size on your photos and your camera
Sensor size and equivalent focal length
The size of your camera’s sensor influences the field of view obtained with a given focal length. The smaller the sensor size, the smaller the field of view and the longer the focal length appears.
In other words, a 50mm lens will not give the same framing depending on the sensor size of the camera it is mounted on.
The size of full-frame sensors is usually used as a reference when talking about focal length.
For sensors of different sizes, we have what is called a “multiplier factor” which allows us to express the focal length obtained as a function of the equivalent focal length for a 24×36 sensor.
To better understand, here is an example with sensors in APS-C format. As we have just seen, the diagonal of these sensors is 28mm while that of the full-frame sensors is 43mm. If we divide 43mm by 28mm we get 1.5. This number is called the multiplier. In other words, if you mount a 100 mm telephoto lens on a body equipped with an APS-C sensor, you will have a focal length equivalent to 100 × 1.5 = 150 mm for a 24 × 35 full frame. With the same lens (and therefore the same focal length), the APS-C sensor produces a more powerful zoom than a full-frame sensor.
Micro 4/3 pickups have a multiplier of 2 (43 divided by 22). Still with a 100 mm lens, this time you would get a focal length equivalent to 100 × 2 = 200 mm in 24 × 35.
In the majority of cases, when we talk about focal length we are talking about “24 × 36 equivalent” focal length.
For example, we say that:
- wide-angles have a focal length of less than 40 mm;
- standard lenses have a focal length between 40 mm and 60 mm;
- the 50mm focal length is equivalent to what a human sees;
- telephoto lenses have a focal length greater than 60 mm.
If your camera is in micro 4/3 format, to choose your lens, you should actually read that:
- wide-angles have a focal length of less than 20 mm (24 × 36 focal length of 40 mm divided by the multiplier coefficient of 2 for a micro 4/3 sensor);
- standard lenses have a focal length between 20 mm (40 mm divided by 2) and 30 mm (60 mm divided by 2);
- the 25 mm focal length (50 mm divided by 2) is equivalent to what a man sees;
- telephoto lenses have a focal length greater than 30 mm (60 mm divided by 2).
Sensor size and pixel size/number
When you look at the specs of a camera, it always says how many megapixels the sensor can record.
A pixel is a sensor cell. It is she who captures the light. Each sensor contains a number of pixels. A sensor could for example contain 6,000 pixels across its width and 4,000 pixels across its height. 6,000 x 4,000 = 24,000,000 pixels. This camera will therefore have 24 Mega Pixels (usually noted 24MP).
When comparing different cameras, we often compare the number of pixels. But what we forget to compare is the size of these pixels. Indeed, the larger these pixels are, the better they will be able to record more light and do so with better quality.
If you take two 24 Mega Pixel cameras, they both contain the same number of pixels. But if one of the sensors is a full frame and the other a micro 4/3, the pixels of the second will be half as large as those of the first. The surface of a micro 4/3 sensor is half that of a full-frame sensor. To fit the same number of pixels, we have to divide the size of each of these pixels by two.
So when comparing two devices, don’t stop at the amount of pixels. Also consider the quality of those pixels. A 24MP camera with a full frame sensor will have better quality than a 24MP camera with a micro 4/3 sensor.
Low light conditions
The larger a sensor, the better it will be at taking pictures in low light. This is because the pixels of large sensors are larger.
This difference is also felt when you practice the long exposure. The more you use a large sensor, the less noise you will have appearing in your photos.
This is also why currently there are appearing on the market devices with a lower number of pixels but sold more expensive than other devices with the same type of sensors but more pixels.
As you can see, the number of pixels is not everything. A 12MP device is sold for the same price as a 42MP device. These two devices have a sensor that is the same size (24mm x 32mm) but the Alpha 7S model has almost 4 times fewer pixels. The pixels of the Alpha 7S are therefore 4 times larger than those of the Alpha 7R. The Alpha 7S is a device that has been designed for photographers who practice long exposure, astrophotography or who need to be able to climb very high in ISO. Depth of field
The size of a camera’s sensor also affects the depth of field you can achieve.
We spoke a few moments ago of equivalent focal length. To obtain the same framing with a smaller sensor, it is necessary to use a shorter focal length. For example, a 25mm lens on a camera with a micro 4/3 sensor will give the equivalent of a 50mm mounted on a camera with a full frame sensor.
But in terms of depth of field, which as you know varies — among other things — depending on the focal length used, a 50mm remains a 50mm and will therefore allow you to obtain shallower depths of field than with a 25mm even mounted on a micro 4/3 sensor.
So a larger sensor allows for shallower depths of field .
Camera size
A larger sensor is physically larger. Even though all the other components are the same, if the sensor is bigger, it will take a bigger box to fit everything inside.
The size of the sensor therefore has an influence on the size of the body of your camera. Generally, the larger the sensor, the larger the case size .
Lens size
The larger a sensor, the larger the compatible lenses as well. For the same focal length, lenses compatible with micro 4/3 sensors are much more compact than those intended for full-frame sensors.
Conclusion: Which sensor size should you choose for your camera?
To summarize what we have just seen, with a larger sensor you will have:
- More pixels and/or larger pixels resulting in better image quality
- A sensor that performs better in low light conditions
- The possibility of obtaining shallower depths of field, very useful for isolating your subject from the background for example.
And with a smaller sensor:
- Greater ease in having long focal lengths (due to the equivalent focal length)
- A more compact camera and lenses
- A lighter system
- A cheaper system
Choose according to your practice
As usual when talking about hardware, the most important thing is to clearly define what you need and how you will use your hardware. There is no best or wrong sensor size. It all depends on what you want to use it for.
For example, if you’re shooting wildlife, you’ll want to opt for a smaller sensor to benefit from the increase in equivalent focal length. A 200mm mounted on a device with an APS-C sensor will give you a 300mm. In addition, the material being less expensive, with a fixed budget you can have a much more powerful telephoto lens on the APS-C platform than if you opt for full frame.
If, on the other hand, you are interested in fashion photography, you will be better off choosing full format. You’ll have higher quality images and the ability to play with shallower depths of field.
Finally, if you are passionate about street photography, the micro 4/3 platform will allow you to have very small, discreet and light equipment. it will be easier for you to blend in with the crowd and also be able to have your device always with you.