However, this does not mean that the resulting images would look identical – changing focal length or camera to subject distance can have a drastic effect on perspective, depth of field and background blur, but that’s another topic that we are not yet ready to discuss. In essence, if you mounted a 24mm lens on this crop sensor camera, then mounted a 36mm lens on a full-frame camera, put them side by side and took pictures of the same subject at the same distance, both would yield a very similar field of view. This basically means that the 24mm lens on the crop sensor DX camera would behave more like a 36mm lens on a full-frame camera in terms of field of view. You take the provided crop factor number, multiply it with the focal length of the lens and you get the equivalent focal length relative to 35mm film / full-frame.įor example, Nikon’s “DX” cameras have a crop factor of 1.5x, so if you take a 24mm wide-angle lens and multiply it by this number, the result is 36mm. “Crop factor” is the ratio of the sensor size to 35mm / full-frame (see below). Since the corners of the image are cropped and thrown away, a wide-angle lens is obviously not as wide anymore, while a telephoto lens makes things appear closer. What is it and what does it do? To make it easier for photographers to understand what the field of view of a lens will look like when compared to a 35mm film or full-frame camera, manufacturers came up with an easy way to calculate the “equivalent” focal length of a lens.
Now that you know what happens to the field of view and the resulting image when using cameras with different sensor sizes, let’s talk about the crop factor. Don’t worry about this for now, as I will explain this in more detail further down below. However, there is one caveat here – sensor resolution, which can make the image appear more magnified. If you take an 8×10 photograph and use scissors to cut out the edges of the photo to make it a 6×8, you are essentially doing the same thing as a crop sensor. This is the problem I referred to earlier – although the lens and its focal length might be the same, capturing the same scene with a smaller sensor than full-frame / 35mm film will yield a different, narrower field of view.Ī good analogy to understand this effect is using a real photograph. The image captured with the smaller crop sensor looks narrower, or more “zoomed in”, while the image captured with the full-frame sensor appears wider. Notice that the two images look drastically different. For example, Nikon often refers to its full-frame cameras as “FX” and their crop sensor cameras as “DX”, while others refer to cameras by sensor size, such as “35mm” and “APS-C”.įor now, all this nomenclature does not matter – look again at the first image and see the resulting photographs on the right side of the camera. Here is a great illustration of various sensor sizes, courtesy of Wikipedia:Īlthough “full-frame” and “crop sensor” are fairly common names for digital camera sensors, some manufacturers refer to cameras and sensors differently. Full-frame sensors have the same physical size as 35mm film (36mm x 24mm), while crop sensors are smaller and can vary in size depending on the system and manufacturer.
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If the sensor covers the full area of the image circle, it is called a “full-frame sensor” and if it covers a smaller portion that throws away or crops part of the image, it is called a “crop sensor”. To understand what happens in the camera with a smaller sensor, take a look at the below illustration: Full-Frame vs APS-C SensorĪs you can see, lenses project a circular image (usually referred to as “image circle”), but the sensor only records a rectangular portion of the scene – the rest of the image is thrown away.
Allowing for a smooth transition from film to digital meant keeping the camera mounts and lenses the same so that those who were already invested in a camera system could simply replace their film camera bodies without having to worry about repurchasing lenses and accessories.īut using a smaller sensor than 35mm film created a new problem – both field of view and captured images appeared narrower, because the corners of the image frame were getting “cropped”, or chopped off. Due to technological challenges and high manufacturing costs, making digital camera sensor sizes that matched the size of 35mm film was impractical, so camera manufacturers started out with smaller sensors in digital SLR cameras (see this article to understand how a DSLR works). If one used a 50mm lens on an SLR film camera, everyone knew exactly what it looked like in terms of field of view and the resulting image, so understanding and discussing different lenses and focal lengths was easy. Common Crop Factors and Equivalent Focal Lengthsīefore digital, 35mm film was a reference format due to its mass adoption and popularity.
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