What Camera Sensor?

Every digital camera has a sensor. Before the digital era, cameras used film. The purpose of a sensor is just the same as in the days of film, and its job is to capture light. Just as there were different sizes of film, there are different sizes of sensor. There are advantages and disadvantages to each type. The sensor will affect the size of a camera, the cost and the final image quality.

What is a sensor?



A Camera Sensor (Sony)

Sensors are created using multiple circuits. Thin wafers of silicon are used to enclose these circuits. Using magic and wizardry, this creates millions of tiny light collecting pockets, commonly known as pixels. If you know a little physics, you will understand that energy changes form. The pixels of a camera collect light energy, which in turn, changes to electrical energy. From this point on, all the collected light becomes data.

My explanation massively oversimplifies a very complicated process. The simplest way to think about a pixel is to zoom into one of your photos. Once you look at the image close enough, you will see the pixel as a tiny square.

How many pixels do you need?

The first digital cameras typically had two or three million pixels which, increased to five and six. Today it is rare for a camera to have less than 12 million pixels, and high-end DSLR’s have between 30 – 50 million. More pixels generally lead to greater detailed photos. However, more is not better in every aspect, and for many, 12 – 20 million pixels is all that is needed.

As I have already mentioned, not all sensors are the same size. However, pixels also differ in size. If I have a full-frame camera and a crop-sensor camera, both with 24 million pixels, then the pixels on the full frame sensor will be larger. A larger pixel is more efficient than a small pixel and can ‘collect’ more light; this increased sensitivity affects the noise that you can see in a photo taken in low-light. The second reason you may wish to have larger pixels, is that they can become ‘full up.’ Once a pixel is ‘full’ of light, that part of the photo becomes a blown highlight. Once you have a blown highlight, the information in that pixel is lost, all you will see is white.

Sensor Sizes



Sensor Sizes. The largest sensor above is ‘medium format’. This is a high end and expensive choice.

If you are looking to purchase a new camera, then these are the sensor sizes that you are likely to come across.

Full Frame – 36 x 24mm

Full frame sensors used to be found only in high-end professional cameras. Now Sony has changed that game and, although not cheap, full-frame cameras are certainly more affordable. The size of these sensors is the same as a frame of negative film. A large sensor is ideal for low-light photography. In addition, full-frame sensors create a very narrow depth of field. A narrow depth of field means that your subject can be sharp and in focus, while the background will be smooth with lots of Bokeh. For Street Photography this effect is rarely sought after.

APS-C – 23.6 x 15.8mm

This is a common sensor size. Many consumer and semi-professional DSLRs have APS-C sensors. For many people, this is a ‘happy medium.’

Four Thirds – 17.3 x 13mm

Both Panasonic and Olympus use Four Thirds Sensors. This size is approximately a quarter of the size of a full-frame sensor. There are still Profesional Cameras with this sized sensor. A four-thirds camera can have an incredible burst rate, and their lenses tend to be smaller. I use the Olympus Em5 ii, which has a 4/3 sensor. This camera system is ideal for my Travel and Street Photography requirements.

One Inch – 9 x 12mm

These sensors are increasing in popularity and are found in many premium compact cameras. Cameras with a one-inch sensor will take superior photos to the ones you can capture with a phone. However, the camera is still small enough to put in your pocket.


One of the smallest sensors you will find and cheap. Due to their size, they are prone to noise.

What Should I Buy?

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When looking at a finished photo, you will not be able to tell the size of the sensor that was used. (This was APS-C on a Nikon D7100)

If you are a beginner, you certainly do not need a full-frame camera. However, there are some reasonably compact full-frame models out there, and the prices of these cameras are coming down. However, remember the body is only part of the cost. Lenses that go with these cameras tend to be large and expensive.

I would recommend to any ‘newbie’ that they start by looking at a camera with a cropped APS-C or a 4/3 sensor. For Street Photography, Fujifilm makes some highly regarded cameras with APC-S sensors. My personal choice is Olympus, which like many Panasonic models, incorporate a 4/3 sensor. Nikon and Canon have models with just about every size on the planet.

Finally, all these sensors are capable of producing stunning images. Do not let sensor size be the final deciding factor of which camera you purchase. Feel and function play a more critical role. If the camera is too large, it may get left at home. Buttons and knobs are essential, too many and a camera is confusing, too few, and it becomes hard to adjust the settings. On the topic of settings, check out the menu and see how user-friendly it is. You pay your money and take your choice. Sensor size should NOT be the only ruling decision!

Take care and keep clicking, Chris.

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