I’m sure you won’t be surprised to hear that every digital camera has a sensor. From the biggest cameras used by NASA to your iPhone, they all work in pretty much the same way. The key to all of them is the sensor that translates light into an image that can then be viewed or printed.

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These sensors are the heart of digital cameras and as such play an integral part in how a photo turns out when you press the shutter button. Cameras typically use two main types of sensors. A sensor that is known as “full-frame” and anything smaller than this sensor is referred to as a “crop sensor”. But before we look at each and their respective pros and cons it’s important to understand their origins.
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A blast from the past

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Back in the 1900s, the 35mm film became the standard for photographers as it struck a good balance between the cost of the film and the quality of the images it produced. This is still the case today with the 35mm film being the most widely used in analogue cameras. When DSLRs were invented, this ratio of the traditional 35mm film was replicated as a digital sensor. So basically, the full-frame sensor is the same ratio as using a 35mm film (36 x 24mm).
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One of the biggest benefits of this was that many photographers who were shooting in film could simply swap to digital and still be able to use their lenses (some without even needing an adaptor).

The crop sensor also followed a previous film size which was created by Kodak in the 90s known as Advanced Photo System (APS). Which incidentally is why these days the most common crop-sensor size is called APS-C. This new film negative was 25.1mm x 16.7mm which is considerably smaller than a 35mm film.
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Crop sensors

The biggest difference between these sensors are the size of them, but more on that later… In a practical setting, the big difference is the field of view that they can capture. In other words if you are standing in the same spot and take a photo at exactly the same focal length with both a full-frame sensor camera and a crop sensor camera, when you look at the photo from the crop sensor camera, it will look like you have zoomed into the scene, even though you haven’t.   

Now this is where is gets a little confusing…

A photo taken with a crop sensor camera needs to be enlarged so that we can see it correctly on a screen. This magnification is called the “crop factor” which is often shown in a number such as 1.5x. 1.6x and so on.

Different manufacturers use different crop factors. For example Canon cameras (like the Canon EOS Rebel SL3 / EOS 250D) have a crop factor of 1.62x, Nikon (like the Nikon Z50) 1.5x and micro 4/3 systems like Panasonic and Olympus have crop factors of 2x.

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This might seem like a pointless bit of information to know, but it makes a big difference in the way a photograph turns out. Let’s say you are photographing a landscape scene with a focal length of 50mm on a full-frame camera. To get the same field of view with a crop sensor camera you need to use a focal length of roughly 35mm.

And this brings us to one of the biggest advantages (or disadvantages depending on what you are photographing) of crop sensors versus full-frame sensors.
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Greater depth of field

As a general rule, the shorter the focal length, the greater your depth of field can be at any given aperture. So using the example above, by shooting at a focal length of 35mm on a crop sensor you will get the same field of view as using a 50mm lens on a full-frame sensor BUT with a greater depth of field.

Clearly for landscape photographers this is an advantage but on the other hand if you are shooting portraits, the shallow depth of field on a full-frame camera will be more desirable.
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But where this might become a hinderance is when you are shooting with wide-angle lenses. For example if you are using a 17mm lens on a Canon APS-C crop sensor camera (which has a crop factor of 1.62x) you are effectively photographing a field of view of approximately a 28mm lens.

Extended zoom

So as you can see above, depending on what you are shooting, the benefit of one may outweigh the other. Another major plus for crop sensors is for those who require a long focal length such as wildlife or sport photographers. This is where a crop sensor can help extend the reach of your lens. For example your 200mm lens could effectively be the equivalent of using a 400mm lens if you were using a micro 4/3 sensor which has a crop factor of 2x. This is useful and much more kind on your pocket than spending money on a brand-new lens.

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The case for full-frame sensors

It may sound like all the arrows are pointing in the direction of crop sensors, but it’s not that simple.

A bigger sensor has several major benefits. The first is what is known as “pixel density”. This is the number of pixels in a given area. Let’s take two cameras (a full-frame and crop sensor) which both have the same resolution (i.e. 18MP). To fit 18 million pixels into a crop sensor the pixels would need to be much smaller and more tightly packed together. Whereas on a full-frame camera the pixels can be much larger. Bigger pixels can capture more light and subsequently produce better quality images when you are faced with high contrast scenes or low light conditions. This is one of the reasons why you will generally find more noise in images taken at high ISOs with a crop sensor camera versus a full-frame camera.

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Better for large prints

A larger sensor doesn’t just mean it can capture better quality photos but also bigger in size. This is especially important when it comes to printing when imperfections are much more noticeable than in digital format.

Basically the bigger that the original image size is, the less it would have to be enlarged for a final large print. For example to turn an image from a micro 4/3 camera into an A1 size print, you would have to enlarge it roughly 10x the original size! Whereas a bigger sensor might only mean having to enlarge your photo 3 or 4 times its original size. This is one of the main reasons that pro photographers who mainly work with print clients favour full-frame cameras as opposed to crop sensors.

What about cost?

Of course a bigger sensor costs more to manufacture and needs a bigger camera body to house it. So this means not only a more expensive and larger camera but heavier as well. In addition to the camera, lenses are also significantly bigger and more expensive for full-frame cameras. But they are also often of a superior quality with better glass and optics than ones made for crop sensors. Even with this in mind, it’s easy to see why for many beginners cost alone becomes the deciding factor when choosing a camera.

Summary

Hopefully by now you have a better understanding of the two main sensor types and can decide which is right for your photography. So as a reminder here are the pros and cons for both full-frame and crop sensors:
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Crop sensor

Pros:

• Cheaper, lighter, and smaller camera bodies than full-frame cameras
• Added focal length for scenarios that require longer lenses such as sport and wildlife
• Easier to achieve greater depth of field
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Cons:

• Image size will be smaller than full-frame cameras which might be problematic when enlarging photos to be printed
• You might not be able to achieve the same wide-angle field of view as a full-frame camera
• Not as easy as full-frame cameras if you want a shallower depth of field

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Full-frame

Pros:

• Better image quality in high contrast scenes and low light conditions with less noise appearing in the image
• Larger image size which allows for bigger size printing
• Wider angle of view possible and shallower depth of field

Cons:

• Much more expensive, heavier, and bigger than crop sensor cameras
• Can’t benefit from magnification in scenarios when longer focal lengths are required

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All photos by Kav Dadfar unless otherwise stated