Crop Factor Explained: Everything You Need to Know
Mirrorless cameras have changed the way we take photos, and understanding crop factor is important to get the most out of your camera. In this article, we’ll dive deep into what crop factor is and how it affects your photography.
What is Crop Factor?
Crop factor is the ratio of the size of your camera’s sensor to that of a 35mm full-frame sensor. It’s also known as focal length multiplier or field of view crop. The 35mm full-frame sensor size is used as a benchmark because it was the most popular film format for many years.
A crop sensor is smaller than a full-frame sensor, and this affects the angle of view of your lens. For example, a 50mm lens on a full-frame camera has a field of view of 47 degrees. However, the same lens on a crop sensor camera will have a narrower field of view due to the crop factor.
Crop factor is calculated by dividing the diagonal length of the full-frame sensor (43.27mm) by the diagonal length of the crop sensor. For example, if your camera has an APS-C sensor with a diagonal length of 28.21mm, the crop factor will be 1.5x (43.27 / 28.21 = 1.533).
How Crop Factor Affects Your Photography
Understanding crop factor is important because it affects the angle of view of your lens. If you’re used to shooting with a full-frame camera and switch to a crop sensor camera, you’ll need to adjust to the narrower field of view. This means that you may need to step back to get the same framing as you would with a full-frame camera.
Crop factor also affects the effective focal length of your lens. For example, if you have a 50mm lens on a crop sensor camera with a 1.5x crop factor, the effective focal length will be 75mm (50mm x 1.5 = 75mm). This can be useful if you’re shooting wildlife or sports and need a longer focal length without having to invest in an expensive telephoto lens.
So, how does crop factor impact focal length? Essentially, it affects the field of view and magnification of a lens. A lens designed for a full-frame camera will have a certain angle of view, but when used on a camera with a smaller sensor (such as a crop sensor), the field of view will be reduced due to the crop factor.
For example, let’s say you have a full-frame camera with a 50mm lens attached. When you take a photo, the lens captures an image with a certain angle of view, let’s say 45 degrees. Now, if you were to use that same 50mm lens on a camera with a crop factor of 1.5, the resulting image would appear as though it was taken with a 75mm lens on a full-frame camera.
This is because the crop factor effectively magnifies the image captured by the lens. In this case, the image would be magnified by a factor of 1.5, resulting in a narrower field of view and increased magnification.
It’s worth noting that this magnification also affects the depth of field of an image. In the example above, the image taken with the 50mm lens on a camera with a crop factor of 1.5 would have a shallower depth of field compared to an image taken with the same lens on a full-frame camera.
This is because depth of field is also affected by the physical size of the sensor, with smaller sensors resulting in a greater depth of field than a larger sensor with the same aperture and focal length. This means that you may need to use a larger aperture to achieve the same depth of field as you would with a full-frame camera.
Crop factor also affects the ISO performance of your camera. The smaller the sensor, the more noise you’ll get at higher ISO settings. This means that if you’re shooting in low light, you may need to use a lower ISO setting to get a cleaner image.
How to Calculate Crop Factor
To calculate the crop factor of your camera, you need to know the size of the sensor. Most camera manufacturers list the sensor size in the camera’s specifications. Once you know the size of the sensor, you can calculate the crop factor using the formula we mentioned earlier.
For example, if your camera has a micro four-thirds sensor with a diagonal length of 21.64mm, the crop factor will be 2x (43.27 / 21.64 = 2).
Understanding Lens Compatibility
Another important aspect of crop factor is understanding lens compatibility. A lens designed for a full-frame camera can be used on a crop sensor camera, but the effective focal length will be different due to the crop factor. For example, a 50mm lens on a crop sensor camera with a 1.5x crop factor will have an effective focal length of 75mm.
Using Crop Factor to Your Advantage
So, we know that crop factor can affect the field of view, depth of field, and overall image quality. But how do you use crop factor to your advantage when shooting with a mirrorless camera?
One of the biggest benefits of crop factor is the ability to get closer to your subject without physically moving closer. This is especially useful when shooting wildlife or sports photography, where it may not be safe or practical to move closer to the action.
For example, let’s say you’re using a mirrorless camera with a crop factor of 1.5x and a 300mm lens. With the crop factor, your effective focal length is now 450mm (300mm x 1.5). This allows you to get much closer to your subject without sacrificing image quality, as long as you’re shooting in good lighting conditions.
Another advantage of crop factor is the ability to use smaller and lighter lenses. For example, a 50mm f/1.8 lens on a full-frame camera is a popular choice for portrait photography. However, on a camera with a crop factor of 1.5x, that same lens becomes equivalent to a 75mm lens, which may be too long for some portraits. In this case, a 35mm f/1.8 lens on the crop sensor camera would provide a similar field of view as the 50mm lens on the full-frame camera.
It’s important to note, however, that using a smaller sensor with a smaller lens may not always result in better image quality. While smaller lenses may be lighter and more compact, they may not be able to capture as much light as larger lenses, resulting in lower image quality in low-light situations.
In addition, the smaller sensor may not be able to capture as much detail as a larger sensor, especially when it comes to dynamic range and high-ISO performance. So while crop factor can be a useful tool in certain situations, it’s not always the best choice for every situation.
In conclusion, crop factor is a technical term that can seem intimidating to new photographers, but it’s an important concept to understand if you’re using a mirrorless camera. It affects the effective focal length, field of view, depth of field, and overall image quality, and can be used to your advantage in certain situations. By understanding crop factor and how it relates to your camera and lenses, you’ll be able to make better-informed decisions when it comes to your photography.