When it comes to digital camera sensors, size can matter. Whether you’re taking selfies, getting quick snapshots, or capturing sweeping scenic vistas, the size of your camera’s image sensor has a major impact on what you see in your viewfinder and how you compose your photos.
Each pixel on a camera’s image sensor captures light in a scene. Through complex processing, the camera converts light into the image you see in your electronic viewfinder or on the LCD screen. The sensor size, as well as the number of pixels that fit onto the sensor, affects how much you see through your viewfinder. Camera sensors range in sizes, from sensors only a few millimeters across, commonly used in smartphones and point-and-shoot cameras; to the larger APS-C crop sensor found in most entry- and mid-level DSLR and mirrorless cameras; all the way up to the full-frame sensors found in many professional series camera models.
APS-C is an industry-wide term that describes digital image sensors roughly 22x15mm in size. An APS-C sensor is significantly smaller overall than the 36x24mm dimensions of a full-frame sensor. The modern full-frame camera is based on the classic 35mm film frame, long deemed an industry standard for professionals and enthusiasts.
Compact digital cameras and early digital SLRs could not accommodate a sensor equivalent to the large 35mm film frame, so camera manufacturers developed smaller sensors. Although an APS-C sensor can produce photographs that rival the 35mm in terms of initial quality, the resulting images appear cropped in comparison to full-frame photos. That’s because the APS-C sensor has less than 40 percent of the surface area of a full-frame sensor or a 35mm film frame.
To capture sprawling landscapes and towering skyscrapers, a full-frame camera lets you fit more of the scene into view than an APS-C crop sensor camera, when using the same lens. For example, fitted with a Canon EF series lens like the EF 50mm f/1.4 USM, the full-frame EOS 5D Mark IV camera will produce a true field of view, whereas the EOS 7D Mark II camera with an APS-C sensor has a 1.6x crop factor that effectively crops the field of view, producing effective lens coverage similar to what an 80mm lens would produce on a full-frame camera. In other words, any lens you attach to an APS-C sensor camera “acts” like a longer lens, providing more of a telephoto effect.