APS-C vs full-frame – the difference explained

The EOS R System mirrorless camera lineup includes models with APS-C image sensors and models with full-frame sensors. RF lenses designed for full-frame cameras can be used with both types of cameras, while RF-S lenses designed for APS-C cameras can also be used with EOS R System full-frame cameras in crop mode. So how do mirrorless APS-C and full-frame cameras compare? How are they similar, how are they different – and which format is right for you?

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.

The 1.6x crop factor applies whether you're using an RF (full-frame) lens or an RF-S (APS-C) lens on an APS-C camera. This is why the RF-S 18-45mm F4.5-6.3 IS STM, despite its wide-angle focal length, provides a field of view equivalent to a standard zoom lens on a full-frame camera.

Because APS-C sensors are smaller, cameras can be made more compact and lighter, which is ideal for street and travel photography. Advances in mirrorless camera design mean that today's full-frame models can also be surprisingly portable though. The full-frame EOS R8 Mark II is comparable in size and weight to an APS-C D-SLR, allowing you to enjoy the benefits of a full-frame sensor without sacrificing portability.

Since a smaller image circle is required from a lens designed for APS-C cameras, however, 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 an advantage in genres such as wildlife, action and sports photography. Using an affordable lens such as the Canon RF 75-300mm F4-5.6 on an APS-C camera gives an effective zoom range of 112-480mm, taking it into super-telephoto territory. The RF 800mm F11 IS STM lens gains an effective focal length of 1280mm on an APS-C camera. You'd need to attach a lens extender or use a larger, heavier and more expensive lens to achieve the same reach on a full-frame camera.

Full-frame EOS R System cameras let you apply a 1.6x crop to achieve the same field of view as an APS-C camera. They also automatically switch to the 1.6x crop when an RF-S lens is attached. Cropping reduces the megapixel count compared with shooting on a dedicated APS-C camera though, so the resulting images have less resolution for large enlargements. But it does provide the creative flexibility to switch between full-frame and APS-C when shooting with the same camera.

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, night-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 remains a good choice for travel photographers, as well as for sports and wildlife photographers who need powerful telephoto reach coupled with freedom of movement. But at approximately 499g (body only), the Canon EOS R8 Mark II gives you full-frame performance in a travel-ready camera that's similar in size to an APS-C DSLR. In fact, it's considerably lighter than the EOS 90D, which weighs approximately 701g (body only), while also offering more intelligent autofocus, a burst rate that's around four times as fast and the image quality benefits of going full frame.

A full-frame camera is particularly well suited to capturing exceptionally wide fields of view, making it ideal for shooting ultra-wide landscapes and confined spaces alike. An APS-C camera can also achieve very wide views with dedicated ultra-wide RF-S lenses, but the 1.6x crop factor of the sensor means a lens such as the RF-S 10-18mm F4.5-6.3 IS STM provides an equivalent full-frame zoom range of 16-29mm. Full-frame cameras can take advantage of a broader selection of ultra-wide lenses, allowing you to capture more expansive views.

One of full-frame's biggest advantages, however, is its ability to produce a shallower depth of field for greater subject separation. This makes it ideal for making a portrait subject stand out against an attractively blurred background. That doesn't mean APS-C cameras aren't a good option for portrait photography. Pairing an APS-C camera such as the EOS R7 or EOS R100 with the lightweight Canon RF 45mm F1.2 STM provides an effective focal length of 72mm – for a classic short-telephoto portrait perspective – while retaining that ultra-fast f/1.2 maximum aperture to help draw attention to your subject.

All Canon EOS R System cameras, from the full-frame EOS R8 Mark II and EOS R8 to the APS-C EOS R7 and EOS R10, are mirrorless cameras featuring the same advanced RF lens mount. This means you can explore the entire range of outstanding RF lenses, regardless of which EOS R System camera you choose. A small number require a full-frame sensor to realise their full creative potential – such as capturing a 190° circular fisheye view with the RF 7-14mm F2.8-3.5L FISHEYE STM – but any RF or RF-S lens can be attached to any EOS R System body.

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 intelligent 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.

If you step up to a full-frame EOS R System camera such as the EOS R8 Mark II or EOS R8, you can continue using your RF-S lenses, although the camera will automatically crop the image to an APS-C area of the sensor.

Other compact, lightweight and affordable favourite RF lenses for full-frame cameras 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. For a 16mm-equivalent view on an APS-C camera, reach for the Canon RF-S 10-18mm F4.5-6.3 IS STM.

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 for close-up photography. 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.

Whether you choose full-frame or APS-C, the EOS R System gives you access to a growing range of RF mount lenses to suit your photography. APS-C offers a compact option with excellent reach, while full-frame opens up more creative possibilities – from wide-angle and low-light shooting to more control over depth of field.