APS-C is the most common crop sensor format, a size of image sensor smaller than a full 35mm frame and used in a huge range of mirrorless cameras and DSLRs. The name comes from the Advanced Photo System film format’s Classic setting, whose frame dimensions the sensor size approximates, at roughly 23.6 by 15.7 millimeters for most makers and a slightly smaller 22.3 by 14.9 for Canon.
Because the sensor is smaller than full frame, it captures a smaller portion of the image a lens projects, which produces a narrower field of view from any given lens. This is expressed as the crop factor, about 1.5x for most APS-C cameras and 1.6x for Canon. A 50mm lens on APS-C frames like a 75mm lens would on full frame, a relationship explained in our guide to full frame versus crop sensor.
That crop has real consequences for how you shoot. The extra reach is welcome in wildlife and sports, where a 300mm lens behaves like a 450mm one and brings distant subjects closer for free. The flip side is that wide-angle work is harder, since a 16mm lens only frames like a 24mm, so APS-C systems offer dedicated ultra-wide lenses to compensate. Manufacturers make crop-specific lens lines for these bodies, such as Canon EF-S, Nikon DX, Sony E, and Fujifilm XF.
APS-C also affects depth of field and image quality. To frame a subject the same way as full frame, you either stand farther back or use a shorter lens, both of which deepen depth of field at a given aperture, so backgrounds blur a little less for the same composition. The crop factor applies to the effective field of view, not to the f-number itself, though the equivalent background blur and noise behave as if the aperture were narrowed by the crop factor.
The smaller sensor area gathers less total light, which historically meant more noise at high ISO, though modern APS-C sensors are excellent and the gap to full frame has narrowed to about a stop. For video, the APS-C frame is very close to the Super 35 format used widely in cinema, which is one reason it remains popular with filmmakers.
The format’s great strengths are size, weight, and cost. APS-C bodies and lenses are smaller, lighter, and cheaper than their full-frame counterparts, which makes them the natural home for enthusiasts, travelers, and anyone who values reach and portability. It sits between the smaller Micro Four Thirds format and full frame, balancing image quality against practicality, and for many photographers it is all the camera they will ever need.
When comparing an APS-C camera to full frame, weigh the whole system rather than the sensor alone. The smaller bodies and lenses, lower prices, and extra telephoto reach are real advantages for travel, wildlife, and everyday shooting, while full frame pulls ahead mainly in very low light and in the ease of achieving extremely shallow depth of field.