Back in the day, when film was all we had, the rectangle that your 35mm film images were captured on was one size: 24mm x 36mm. Today, this is roughly the same size as a digital camera’s full-frame sensor. So, when you hear the term ‘full frame’ this means a camera with a sensor that is pretty much 24mm x 36mm.
DSLR sensors are much larger than your average smartphone.
A crop sensor is physically smaller than a full frame sensor. Each manufacturer differs and there are many different types of crop. Such as, Canon has a 1.3x and 1.6x crop sensors. In real life, this crop factor means that your image will be more zoomed in than if you took it on a full frame camera. If you take the same image from exactly the same spot at exactly the same focal length with a full frame and a crop, it will be more zoomed in when you use the crop sensor.
Due to the crop, it will mean that when you buy lenses for crop sensor cameras, you must allow for it to act like a longer lens. So, a 50mm lens will become an 80mm lens when using a 1.6x crop. Most of the time, you see the 50mm lens described as the best lens for portraits – but the actual ideal focal length is 80mm. However, due to crop factor on lenses, a 50mm will become closer to the 85mm when you’re using it with a crop.
The same image taken at using a 17mm focal length on a crop sensor and full frame.
For most users, the difference between full frame and crop doesn’t have a tremendous impact in real life. But, it will influence the lenses you choose, and using a crop sensor can become a real advantage if you’re shooting wildlife or sports, as getting that extra boost from the sensor can get you closer in to the action.
On the other hand, for images such as landscape and architecture, shots as super-wide angle as possible are preferred so you’d be better off with full frame. Also, if you need to shoot in conditions with lower light, you will encounter more issues with a crop sensor.
Full-frame tends to hugely out-perform crop sensors when it comes to low light, due to the actual size of the pixels on the sensor itself. If you look at what a 12MP sensor looks like on a crop and full frame, the pixels on the full frame are far larger.
You often see this explained with a watering can and buckets analogy. If you imagine each of the pixels on the sensor is a bucket, and you were to pour water over the sensor with a watering can, the pixels on the full frame sensor would be able to collect far more water than the crop sensor, as the area that can collect the water is larger and the buckets themselves are larger.
Despite having the same number of pixels, the ones on the full frame are larger and can therefore gather more information and light.
In real life, light falls onto the sensor and the sensor gathers it much like it would have done with the water in the watering can analogy. This means that the full-frame sensor can gather far more light than the crop sensor due to the larger size of the pixels and the fact that it has a larger area to collect the light on. So, if you’re shooting in lower light conditions regularly, you may want to think about investing in a full frame model.
One of the main deal-breakers between the two is price and size. Full frame does come with a generally higher ticket price, creating a larger sensor is more expensive and thus drives up the price of the camera as a whole. As the price is already driven up due to the manufacturing costs, the feature sets tend to be higher spec than crop sensor models too, increasing the prices further.
Of course, full frame and crop aren’t the only sensors on the market. You also have micro four thirds, medium format and many more. Each sensor will have a different effect on your image and it’s always worth carefully considering a camera’s sensor before you invest in a new body.