Did you know that your camera’s crop factor can change the performance of your lens? Shooting with a 50mm focal length on a cropped sensor camera is not the same as shooting with a 50 on a full frame camera.
A camera’s crop factor is an important photography concept. Unfortunately, it’s not always understandable when you first encounter it. It’s important, however, because it can change the zoom of your photo over and above the zoom provided by your lens.
Let’s start by defining focal length as it relates to photography, and then we’ll move on to the crop factor. The focal length of a lens is a measurement, in millimeters, of the distance between the lens element and the camera sensor. Each lens works at one focal length, or at a range of them: 50mm, 70-200mm, etc.
The longer this length, the farther you can zoom in to far off objects. In other words, longer focal lengths make your subject look closer and larger. Shorter focal lengths make your subject look smaller and farther away.
Each focal length, when combined with a sensor of a given size, produces an angle of view. A lens’s angle of view measures the size of a scene in front of it that the lens can capture. The angle of view is measured in degrees – think back to geometry and those 360 degrees in a circle.
The longer the focal length, the more narrow the angle of view. Lenses are generally categorized according to this focal length/angle of view designation.
You can see from the photos below that the photo taken with a 122 mm focal length includes more of the scene from left to right and top to bottom. Its angle of view is 20.1°. The photo taken at 200 mm, on the other hand, has an angle of view of 12.3°. You can only see part of the wall on the left and the very tip of the rail on the right.
That’s all easy to understand, right? Let’s muddy the waters a bit.
In addition to focal length, the size of your camera’s sensor also affects the angle of view. If you have a cropped sensor (you shoot with something other than a full frame camera), your angle of view is going to be smaller than it would be with the same lens on a full frame. We call the difference between the two a crop factor.
If I had used my old 7D, which isn’t a full frame, to take the above photos, they would have been about the size of the images inside the white boxes below.
This is one reason that many people prefer cropped sensors for sports & wildlife photography. Your photo looks more zoomed in with the same lens.
We call these cropped sensors on Canon and Nikon dSLRs “APS sensors.” So, if you have an APS sensor, know that, regardless of the lens you’re using, your angle of view will be smaller than it would be on a full frame camera. And your zoom will be more pronounced!
To further complicate matters further, the amount of the crop factor varies from manufacturer to manufacturer and camera to camera.
Most Canon APS sensors these days have crop factors of 1.6. That means that if you’d like the same angle of view as that provided by a 50mm on a full frame sensor, you divide the focal length (50mm) by the crop factor (1.6). 50/1.6= about 31mm. So, if you want the effect of a 50mm lens on a Canon, you might want to shoot at 30 to 35mm instead.
Most Nikon APS sensors, on the other hand, have a slightly smaller crop factor.
Four Thirds cameras, like my mirrorless Olympus, have a crop factor of 2. That means that I have a 25mm lens instead of a 50 for this camera.
This table summarizes the generally accepted lens categories for cropped Canon, Nikon & Four Thirds sensors:
Why is angle of view important for your photography?
The angle of view is going to affect the mood and composition of your photo hugely. The remaining lessons about lenses in the Guided 365 Project teach you to associate the lenses on your camera with specific effects – distortion, background compression, etc. There is no need to memorize the table above, but do get a feel for where your lenses fall on it. Being familiar with it will help you use focal length as a compositional tool far beyond simply zooming into or away from your subject.
Today’s Assignment (for Guided 365 Participants Only)
- What to Shoot: Lines.
- How to Shoot: On manual mode.
- Hashtag: #Guided365, #Day148Guided365
- Include with Post: Your settings. Is your sensor cropped or full frame? How would your image have been different if you had shot on the opposite type of camera?
- Carry forward from this assignment: You get more zoom for your buck on cropped sensors.
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