What Is Crop Factor?
The crop factor is the formula to determine the focal length based on the camera’s sensor size. Based on the full-frame 35mm format (sensor size), a full-frame SLR, DSLR, or mirrorless camera system has a crop factor of one. In other words, if you put a 35mm lens on a full-frame camera, then you have an effective 35mm focal length. 35mm multiplied by one is 35.
Where the real math comes into play is when you’re dealing with other popular formats, like APS-C camera systems. Most of these cameras will have a crop factor of 1.5 (Sony, Nikon) or 1.6 (Canon). So a 35mm lens on a Sony APS-C camera would have an equivalent focal length of 52.5mm, roughly that of a 50mm lens on a full-frame camera. 35mm multiplied by 1.5 is 52.5.
There are many other camera systems out there that have different crop factors. Micro Four Thirds cameras have a crop factor of two, whereas smartphone cameras have different and varying crop factors.
Check the owner manual or look up online to know the crop factor for your camera.
What This Means for Your Choice of Lenses
Depending on what kind of photography interests you, your choice of lenses may be complicated by crop factor if you need a specific focal length. For instance, if you shoot a lot of landscape photography and need a wide focal length like 24mm, it’s good to know that full-frame cameras will give you that focal length for just about any 24mm lens you use with it.
But if you have an APS-C camera, for example, you’re going to want to shop around for a 16mm lens for most camera brands (1.5 crop factor) or a 15mm lens if you own a Canon APS-C (1.6 crop factor). You need to divide the crop factors to get the equivalent 35mm focal lengths in these instances.
You may also want to learn the differences between prime and zoom lenses before purchasing a new camera lens.
A Deep Dive Into Crop Factor
The following video goes in-depth and helps visualize crop factor and how it applies to photography.
Not to be confused with the crop factor, cropping in photo editing is helpful too when you’re looking to achieve other focal lengths.
Crop Factor Matters
From the right focal length down to the right choice of lens for the job, it’s important to know your camera’s crop factor. It will immensely help your photography by enabling you to capture your subjects at the correct focal length.
