APS-C vs full-frame – the difference explained

Just like Canon's DSLR range, the EOS R System mirrorless lineup now includes both APS-C and full-frame cameras, with the APS-C EOS R7, EOS R10, EOS R50 and EOS R100 alongside full-frame models including the EOS R8, EOS R6 Mark II, EOS R5 and EOS R3.

The main difference between APS-C and full-frame is the physical size of the image sensor – full-frame sensors are larger than APS-C sensors – and other differences between the two types of cameras flow from that. But as with most things, bigger isn't necessarily better, and each format has its own key advantages.

The active area of Canon's APS-C format image sensors measures 22.2x14.8mm, a close match to a frame of APS-C format photographic film.

The APS (Advanced Photo System) format was originally introduced in 1996, as a new type of photographic film cartridge. In most film cameras of the day, you could also choose different aspect ratios while shooting, including C (Classic) with the same 3:2 aspect ratio as conventional 35mm film cameras, H (High definition) with a widescreen 16x9 aspect ratio, and P (Panoramic) 3:1.

APS-C also corresponds to the Super 35 video format and became a popular choice of image sensor size for Canon EOS digital SLR (DSLR) cameras, as well as for EOS M series mirrorless cameras.

Canon's full-frame image sensors have an active surface area of 36x24mm, the same size as a frame of 35mm film.

The 35mm film format dates from 1889, when it was introduced as a standard width for movie film. It soon became the norm for still photography, and was carried over into full-frame digital cameras including Canon's full-frame EOS DSLRs and EOS R System mirrorless cameras.

Both APS-C and full-frame sensors produce images with a standard aspect ratio of 3:2, and APS-C sensors can have the same number of megapixels as full-frame sensors. However, a full-frame image sensor is physically about 63% or 1.6x larger than an APS-C format image sensor.

This physical size difference between the two sensor types determines what the camera "sees". All lenses produce a circular image, which means that a full-frame compatible lens needs to have a large enough circumference for the image to overlap the corners of a rectangular full-frame image sensor. If you use the same lens on an APS-C format camera, the smaller image sensor will utilise only a smaller region in the centre of the same image circle. In effect, compared to the image on a full-frame sensor, the image is cropped.

Because the APS-C sensors in Canon cameras are 1.6x smaller than the sensors in Canon full-frame cameras, the "crop factor" is 1.6x. This means that shooting with a 50mm standard lens on an APS-C camera gives you the same field of view as shooting with an 80mm telephoto lens on a full-frame camera (50 x 1.6 = 80). In the same way, using a full-frame 100mm lens on an APS-C camera gives the same field of view as a 160mm lens on a full-frame camera. For this reason, crop factor is also sometimes known as "focal length multiplier", telling you the effective focal length of the lens you're using.

If you want to work this out when you're using an RF, EF, RF-S, EF-S or EF-M lens on an APS-C camera, you can use the Effective Focal Length calculator in the free Canon Photo Companion app.

Crop factor applies to all full-frame lenses used on APS-C format cameras, including both EF and RF lenses. EF lenses can be used on all APS-C R System cameras with any of the range of EF-EOS R Mount Adapters.

Because APS-C sensors are smaller, cameras can be made more compact and lighter, which is ideal for street and travel photography. Since a smaller image circle is required from a lens designed for APS-C cameras, the lens can be smaller and lighter, and consequently can be more affordable.

The crop factor of an APS-C sensor makes smaller or more distant subjects larger in the frame, which in effect increases the effective focal length of any lens by 1.6x. This can be a major advantage in genres such as wildlife, action and sports photography. Using a high-performance yet affordable lens such as the Canon EF 70-300mm f/4-5.6 IS II USM on an APS-C camera gives an effective zoom range of 112-480mm, taking it into super-telephoto territory. The comparably-priced RF 100-400mm F5.6-8 IS USM lens gains an effective focal range of 160-640mm on an APS-C camera. You'd need a larger, heavier and more expensive lens to give the same reach on a full-frame camera.

You could crop images from a full-frame camera to create the same effect, but the megapixel count would be reduced, so the resulting images would be smaller and hence less sharp when enlarged again. Shooting with an APS-C format camera also saves the time and effort of manually cropping images at the editing stage.

Because a full-frame sensor has a wider field of view, a full-frame camera is ideal for sweeping landscapes, ultra-wide architectural interiors and astrophotography, and for creative effect when you want to exaggerate the perspective between foreground and background areas.

As a general rule, especially at wider apertures (lower f-numbers), full-frame cameras can produce a narrower depth of field than APS-C cameras, meaning that a smaller part of the image is in sharp focus and more of the background is blurred. This is often ideal in still life and portrait photography, and in any other shooting scenario where you want to isolate the main subject by throwing the background out of focus.

One further advantage of a full-frame sensor relates directly to its larger size. Other things being equal, the individual photosites or light receptors on a full-frame image sensor will be physically larger than those on an APS-C sensor with the same megapixel count. They therefore have more light-gathering potential and can capture more information, with less image noise or grain, particularly at high ISO settings in low-light conditions. This is a great asset in indoor portrait and wedding photography, as well as for handheld shooting at twilight, nigh-time cityscapes, and any time you need to keep shutter speeds sufficiently fast to freeze motion in poorly-lit scenes.

Full-frame cameras are sometimes said to be more "professional" than APS-C cameras, and certainly they are usually larger, making them better suited for use with big telephoto lenses. However, thanks to the increased reach you get with an APS-C camera, you might not need such a big telephoto lens in the first place. APS-C can remain the best choice for travel photographers, as well as for sports and wildlife photographers who need powerful telephoto reach coupled with freedom of movement.

As wildlife photographer Dani Connor commented after her first shoot with the Canon EOS R7, "It allows me to get closer to my subject without having to use a big, heavy lens. It's the perfect sort of camera if you're a bird photographer, because birds are often quite small and quite far away."

Full-frame cameras might be well suited for shooting ultra-wide landscapes but, conversely, because of full-frame's narrower depth of field, it can also be easier to achieve front-to-back sharpness in a landscape shot using an APS-C camera. Plus, although full-frame cameras typically produce shallower depth of field and thus can help a portrait subject stand out against an attractively blurred background, other factors such as aperture also come into play – the APS-C EOS R10, EOS R7, EOS R50 and EOS R100 will work well for portraiture with a lens such as the compact Canon RF 50mm F1.8 STM, which has an ideal 80mm effective focal length and a fast f/1.8 aperture.

All Canon EOS R System cameras, whether they are full-frame or APS-C format, are mirrorless cameras featuring exactly the same advanced RF lens mount. This means that if you opt for the EOS R7 or EOS R10, or even the EOS R50 or EOS R100, you can take full advantage of the entire range of outstanding RF lenses. In addition to lenses with cutting-edge focusing technologies and optical quality, the RF mount provides hugely greater data transfer speed and bandwidth between lens and camera, enabling advanced AI-powered autofocus acquisition and tracking with incredible speed and precision, new levels of image stabilisation, real-time lens optimisation, and many other advances.

With the introduction of the EOS R7 and EOS R10 came new RF-S lenses specially designed for RF mount cameras with APS-C sensors. The RF-S 18-45mm F4.5-6.3 IS STM standard zoom, with a 35mm equivalent effective focal range of 29-72mm, is comparatively tiny with its retractable design, weighing a mere 130g, while the RF-S 18-150mm F3.5-6.3 IS STM delivers an even greater zoom range – 35mm equivalent effective focal range 29-240mm – and still weighs only 310g, making it a highly versatile, all-in-one lens for everyday shooting and travel photography.

Other compact, lightweight and affordable full-frame compatible favourite RF lenses include the Canon RF 16mm F2.8 STM, which on the EOS R7 and EOS R10 gives a still generous wide field of view equivalent to a 25.6mm lens on a full-frame body. The Canon RF 35mm F1.8 MACRO IS STM works brilliantly as a standard prime, with a 56mm effective focal length on APS-C EOS R System cameras, complete with optical image stabilisation and a 0.5x macro magnification factor. The Canon RF 50mm F1.8 STM is an excellent portrait lens, combining an effective focal length of 80mm on an APS-C camera with a fast f/1.8 aperture for a tight depth of field. For travel and street photography, RF 28mm F2.8 STM gives an effective focal length of 45mm when paired with the EOS R10 in a light, compact pancake design.

You can also use the wide range of EF and EF-S lenses on APS-C R System mirrorless cameras, with no loss of quality or functionality, thanks to the range of EF-EOS R Mount Adapters.