If you’re in the market to purchase a new camera or lens, you need to be aware of the crop factor. With so many different cameras—with different sized sensors—on the market today, this is a term that’s definitely going to come up. But, what is crop factor and how does it affect your photography? 

This is a beginner’s guide meant to simplify a somewhat complex topic. We’ll define crop factor; explain how it’s calculated; help you determine what, if any, your camera’s crop factor is; and describe what effect it has on your photography. Then, we’ll offer advice on how to consider this when shopping for lenses.

Full frame cameras do not have a crop factor.
Photo by Satria Bagaskara from Pexels

What is crop factor?

So much of what we do today in digital photography has roots in film and this is true of camera sensor size, too. In the days of film, 35mm was the standard format. So when you used a particular focal length lens, say 50mm, on any SLR film camera the result was always the same. 

However, in the early days of digital cameras, it was too expensive and impractical to make camera sensors that were as large as 35mm film, so manufacturers started out with sensors that were smaller. But, they wanted to ease the transition from film to digital, so they kept the mounts and lenses the same to prevent photographers from having to purchase all new gear.

As you can imagine, using a smaller than 35mm sensor posed a problem. The smaller sensor captured less of the scene, essentially cropping the image. Hence, we have what’s called the crop factor. 

What’s more, not all sensors are the same size. Besides full-frame cameras that are all 35mm, different manufacturers use differently sized sensors in their cameras.

common sensor sizes and their crop factors

Why use crop factor?

Now that you understand why we have a crop factor, let’s talk about what it is used for. Remember above we mentioned that back in the film days, you always knew what a particular focal length would look like when shot. 50mm on a full-frame camera always looks the same. But, when you shoot with a 50mm lens on a crop sensor camera, it’s different depending on the camera’s crop factor.

The crop factor gives photographers an easy way to calculate the equivalent focal length of a lens if you were shooting with a full-frame camera. For example, a 50mm lens on a full-frame camera is 50mm. But, using a 50mm lens on an APS-C camera with a crop factor of 1.5x is the equivalent of shooting with a 75mm lens on a full-frame camera.

Basically, crop factor is the ratio of the sensor size to 35mm/full-frame. Once you know your camera’s crop factor, use it to figure out the equivalent focal length of the lens you’re using. Simply multiply it by the lens’s focal length.

For example, a 24mm lens on a Canon camera with a 1.6x crop factor is the equivalent of a 38mm lens. (24 x 1.6 = 38.4). Here, you lose quite a bit of width. So if you want to shoot wide, you’ll need to find a super wide-angle lens to compensate for the loss.

A 400mm lens on a camera with a 2.0x crop factor is the equivalent of an 800mm lens. (400 x 2 = 800). In this case, you can see how crop sensor can be used to your advantage. You can use less expensive lenses on cheaper crop sensor cameras to reach focal distances that would be extremely expensive with a full-frame camera and an 800mm lens!

What crop factor does your camera have?

Unless you are shooting with a full-frame camera, you likely have a crop sensor camera. Here’s a list of some common cameras and their crop factors:

  • 1.3x: Canon EOS 1D, Canon EOS 1D Mark IIN;
  • 1.5x: Nikon D40, Nikon D50, Nikon D70, Nikon D70s, Nikon D80, Nikon D200, Nikon DX, Minolta 7D, Fuji S3 Pro, Fuji X-A1, Fuji X-M1, Fuji X-E2, Pentax K-5, Pentax K100D, Pentax K110D, Pentax K10D, Samsung NX1;
  • 1.6x: Canon EOS 300D, Canon EOS 400D, Canon EOS 20D, Canon EOS 30D, Canon 70D, Canon EOS M2, Canon EOS 7D Mark II;
  • 2.0x: Micro Four Thirds Olympus OM-D Series, Panasonic DMC Series.

If your camera isn’t listed, you can easily do a search online to find out what its crop factor is.

How does it affect your photographs?

We briefly mentioned above, depending on your camera and what lens you’re using the crop factor can have a drastic effect on the focal length of your lens. We used the example that a 400mm lens on a full-frame can be an 800mm super telephoto lens on a Micro Four Thirds camera! 

However, this is where it can be confusing for beginners. The crop factor is not actually extending the focal length of your lenses. It is really just cropping in to give the appearance of a longer lens, as shown in the illustration below.

full frame vs. crop sensor

Common crop factors and equivalent focal lengths

Here’s a chart of several lens focal lengths along with some common crop factors and their equivalent focal lengths:

common crop factors and their equivalent focal lengths

Lenses and crop sensor cameras

If you already have a camera and are in the market to buy a new lens, you’ll be presented with multiple options. First, you’ll need to make sure you look at lenses that are compatible with your camera’s mount. Then you’ll be able to choose between two options:

  • Crop-sensor lenses;
  • Full-frame lenses.

If you have a crop-sensor camera, you can use either crop-sensor lenses or full-frame lenses. If you shoot with a full-frame camera, crop-sensor lenses will probably fit on your camera, but they won’t work with it. And, if they do, they will leave dark corners on your images. That’s because crop-sensor lenses are made for smaller sensors.

A word to the wise: if you have any intention of upgrading your crop-sensor camera to a full-frame camera in the future, buy full-frame lenses from the start. That way, you’ll still be able to use them with your new camera, assuming you stick with the same brand. If you invest in crop-sensor lenses now, you’ll have to re-invest in all-new glass when you get a full-frame camera. Additionally, full-frame lenses tend to be of higher quality and better build.

Final thoughts

Hopefully, this article shed some light on a fairly complex topic. While having a smaller sensor that crops a large part of your image might not seem ideal (and for many photographers, it isn’t), it comes in quite handy for sports and wildlife photographers, who love the extra reach they get. So, understanding what crop factor is and how it affects your images is what’s most important. And, you’ll be most informed when the time comes to make your next camera or lens purchase.