Camera Sensor Crop Factor Explained

By May 1, 2015Photography Tips

As I write more photography tips on this blog I feel like my job is to identify areas of concern for people that want to improve their photography. While most people know that they need to improve with their lighting, know they need to understand the settings on their camera and know that they need to improve their editing skills I feel one of the scariest things is for these photographers to be completely oblivious of certain aspects of photography that can have a significant impact on all of their pictures. So let me introduce you to Sensor Crop Factor.

For those of you that have purchased a new lens for your DSLR how many of you bought a prime lens, maybe a 50mm lens? Did you know that you might not actually be shooting at the focal length of the lens that you have on your camera? Confused? Most cameras that are produced don’t have a Full Frame sensor but actually sensors that are smaller. Since most high quality lenses are built to work with Full Frame sensors you will actually get an effective focal length much longer than you would expect. In fact, most smaller sensors have a Crop Factor of 1.5x to 1.6x. This means that the 50mm lens you bought for your Canon T5i is actually shooting at the equivalent of 80mm.

Camera Sensor Crop Factor

What is crop factor?

Crop Factor Diagram

Most high quality lenses are built to work with Full Frame sensors. Seen in the diagram above, when projected onto smaller sized sensors a smaller portion of the image is recorded. Some people I’ve spoken with about Crop Factor have confused it with cropping while editing. Crop factor is 100% determined by the camera’s sensor, you can’t choose to include more or less of the image. When cropping in editing software, you have the full sized image and you can crop to smaller size that fits your desire.

What’s the crop factor of my camera?

The best place to go to find out this information is either the website of your camera manufacturer or bhphotovideo.com. Find your camera model and look through the specifications to find out what sensor your camera has. If it doesn’t call out the crop factor but says a name for the sensor type, APS-C being an example then search the crop factor of that sensor.

How do I compensate for crop factor?

Most lens manufacturers do have lines of lenses that are built specifically with crop factor sensors in mind. However, as a general rule of thumb, the highest quality lenses are built for Full Frame Sensors. So if you’re in the market for a new lens and want the best quality, you can use this tip. Once you figure out what the crop factor of your sensor is you can do a little math to find out what lens you should buy to achieve your desired focal length. Want to shoot at 50mm, a common focal length for many photographers? You can buy a high quality 35mm lens which will give you the equivalent of 56mm. I generally guide people with cropped sensors towards 35mm because if they choose to upgrade to a full frame sensor, a 35mm is a great lens to have. Look out for a future post where I’ll recommend some lenses to invest in.

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