Since the introduction of mass marketed digital cameras around 20 years ago, film has been replaced with an electronic sensor inside the body of the camera.
Just as there were many different sizes of film over the years — the same can be said for sensor sizes. As larger film cameras such as “645” format, were more expensive than the compact 35mm formats — this pattern remains the same in the digital age. Additionally, there are now even smaller formats that are more affordable.
The question is, why does this matter, and what do you need to consider with respect to sensor size when deciding on a camera to purchase?
What exactly is a sensor?
A sensor is an electronic device with tiny light sensitive areas called photosites or pixels over its surface — much the same way as your mobile phone or TV screen is made up of millions of little light producing dots. The difference is the camera's sensor, records light rather than producing light. As the sensor has millions of these tiny pixels, each pixel can only capture a small quantity of light or photons. The larger the pixels, the more light they can capture. The more light that is captured, the higher the image quality.
So it sounds like we want big pixels — how do we get them?
This is where things get a bit tricky. If big pixels are what we want, then we can't have too many of them on the sensor. Sensor resolution now comes into play as higher megapixel values mean smaller pixels.
Given the same sensor size, a 6 megapixel camera will have pixels 4 times the size of a similar 24 megapixel camera. Therefore, all other things being equal, the 6 MP camera should have much higher image quality.
But what if we want both high resolution and the ultimate image quality? A solution is to use a larger sensor so that we can have large pixels and more space to place them.
Now just to make things a bit more complex, we have recently seen the introduction of new sensor technologies (such as backside illumination) that has enabled larger pixels, while keeping the resolution of the sensor the same. Lower native sensor sensitivity has also been introduced on a number of models that has enabled each pixel to record light for longer periods of time, which in turn enables higher image quality.
Most of these new sensor developments have shown up in the standard 35mm full frame models first, but they are also progressively finding their way into the smaller and larger sensor format cameras.
Keep in mind, that as sensor size increases, the size of the camera and associated lenses tends to increase and price follows suit.
On the other side of the equation, as modern sensor designs have dramatically improved over the last few years — even the image quality from mobile phone sensors is amazing, considering what the early professional digital camera’s delivered.
Canon full frame EOS 5DSr with EF 85mm F1.2
Lastly, sensor size plays an important role in shallow depth of field composition. A larger sensor, when used with an equivalent speed and field of view lens, will yield a shallower depth of field image as compared to one captured with a smaller sensor. This is one of the key reasons portrait and fashion photographers have desired larger format systems over the years. In the digital realm, larger format systems such as the Fujifilm GFX series are now more affordable than ever. The current state-of-the-art GFX 100 MP camera is on the order of a quarter of the price of the previous generation of studio cameras — and it can go anywhere vs. being stuck on a studio tripod tethered to a computer.
Now don't think for a minute that you have to have a large sensor in order to get the shallow depth of field look. Full frame cameras can often yield results just as shallow as the big sensors thanks to the wealth of fast lenses that are available. A fine example would be Nikon's new 58mm F0.95 Noct that can produce a razor thin focus area! Canon shooters have had 50 and 85mm F1.2 lenses available for years, and the rare EF 50mm F1.0 can often be found for sale on the used market.
Canon APS-C EOS D60 with 50mm F1.8
Even the smaller formats such as APS-C don't miss out on this style of shooting thanks to the 50mm F1.8 lenses that are available. These affordable cameras and lenses keep the cost conscious shooter happy in the “shallow end” of the pool while still producing great portrait results worthy of exhibition.
Alas, let’s not forget about the point and shoot cameras.
The massive uptake in mobile phone photography has taken a huge bite out of this market, but there are still some gems to be found featuring larger sensors than smartphones.
The most popular is often referred to as the 1 inch series manufactured by Sony. They have a full line up of cameras ranging from vest-pocket sized to superzoom using this popular sensor. For many smartphone shooters looking to up their game, these RX series cameras from Sony are a great place to start shopping.