Crop Factors and Why Does The Size of My Sensor Matter ?

Crop Factors and Why Does The Size of My Sensor Matter ?

I will begin by describing a digital sensor, a digital cameras sensor is the part of the camera that actually records the image, it exists behind the lens and when you press the shutter all of the light in front of the lens pours onto the sensor and is recorded by millions of light sensitive spots called photosites, the bigger a sensor is and the more photosites there are, the higher quality the recorded image will be. 

So when digital cameras first came into the mainstream a lot of photographers who previously shot on film were confused, mainly because their lenses on these brand new digital cameras weren't behaving normally. For example, if a photographer took a photograph with a 50mm lens, it’s quite likely the resulting image would have the angle of view of a 75mm lens. 

So, to help photographers understand the transition between film and digital a little better, a decision was made to call any digital sensor of the equivalent size to 35mm film a full frame sensor, and any sensor that was smaller than 35mm film was given a crop factor depending on how small the sensor was. I.e. a sensor with a crop factor of 1.5 would be larger than a sensor with a crop factor of 2. A sensor with a crop factor of 2 is half the size of a full frame sensor and so on. 

So, when you take a photograph with a 35mm lens your camera should have recorded an image with an angle of view of around 62 degrees. However, if you take a photograph with a 35mm lens on a camera that has a sensor with a crop factor value of 1.5, the angle of view that will have been recorded would be more like 93 degrees. This is because smaller sensors record less of the image and so to balance this phenomenon out, you need to use wider lenses. Therefore to capture a field of view of around 62 degrees on a camera with a crop sensor of 1.5, you would need a lens thats 23.5mm. Are you with me ?

So, the image above I photographed in London on a full frame camera with a 24mm lens. The box in the middle shows the area that would have been captured had I used a 24mm lens with a camera that had sensor with a crop factor of 1.5. 

However, had I used a camera that had a crop factor of 2 even less would have been captured. So there you have it, a small explanation into crop factors and sensor size.

Thanks for reading ! 

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