Most entry-level and mid-price DSLRs sport an APS-C sized sensor, with the physical dimensions measuring 23.6 x 15.7mm (22.2 x 14.8mm on Canon DSLRs).
A full-frame sensor on the other hand has dimensions of 36 x 24mm - the same size as a frame of 35mm film, hence the name 'full-frame', and offering a surface area 2.5x larger than an APS-C sized sensor. This allows for larger photosites (pixels) on the sensor, delivering better light gathering capabilities, which in turn means better image quality - especially at higher sensitivities.
Full-frame DSLRs used to be the preserve of professional photographers, but as the costs have dropped and lower-cost models have started to appear, many serious amateurs and enthusiasts can now enjoy the benefits of full-frame photography.
We should also mention full-frame mirrorless cameras. These aren't DSLRs strictly, but the Sony A7 series cameras and now the Leica SL are muscling in on the full-frame DSLR market, and are particularly interesting for those who also need to shoot video.
In the meantime, here are the best full-frame DSLRs you can buy right now:
1. Canon EOS 5D Mark IV
One of the most complete DSLRs we've seen
Sensor: Full-frame CMOS | Megapixels: 30.4MP | Autofocus: 61-point AF, 41 cross-type | Screen type: 3.2-inch touchscreen, 1,620,000 dots | Maximum continuous shooting speed: 7fps | Movies: 4K | User level: Expert
Canon's 5D series of cameras has a rich heritage – the original EOS 5D bought full-frame photography to the masses, the Mark II unleashed Full HD video capture for the first time on a DSLR, and while the Mark III became a firm favourite amongst photographers. The 5D Mark IV pretty much tweaks and improves on everything before it. With a new sensor that delivers pin-sharp results, a 61-point AF system that's incredibly advanced and some very polished handling, the 5D Mark IV has to be one of the best DSLRs we've seen.
Read the full review: Canon EOS 5D Mark IV
2. Nikon D810
It may have recently been ousted from the top spot, but this is still a terrific choice
Sensor: Full-frame CMOS | Megapixels: 36.3MP | Autofocus: 51-point AF, 15 cross-type | Screen type: 3.2-inch, 1,228,800 dots | Maximum continuous shooting speed: 5fps | Movies: 1080p | User level: Expert
It might be getting on a bit, but the Nikon D810 is still one of the best DSLRs around. Images from Nikon's megapixel monster are bursting with detail, whilst its 1200-shot battery life puts the 5DS in the shade. We're also fans of the D810's clarity micro-contrast adjustment with its video-friendly Flat mode for maximum dynamic range. The 51-point AF system copes well with tricky focussing situations, mainly because both the AF and metering systems are taken from the now ex-range-topping Nikon D4S. Relatively compact dimensions and the unusual (at this level) inclusion of a pop-up flash further ensure that the D810 doesn't disappoint.
Read the full review: Nikon D810
3. Canon EOS 5DS
Proof that more can mean better: the 5DS sets a new standard for DSLR photography
Sensor: Full-frame CMOS | Megapixels: 50.6MP | Autofocus: 61-point AF, 41 cross-type | Screen type: 3.2-inch, 1,040,000 dots | Maximum continuous shooting speed: 5fps | Movies: 1080p | User level: Expert
With 50.6 million effective pixels, the 5DS is by far the highest resolution full-frame DSLR on the market. The same goes for the 5DS R, which is identical to the 5DS, but features an anti-aliasing cancelation filter over the sensor to help resolve a little more detail. Pixel-packed sensors can be compromised, but not here. Image quality is superb, with fantastic detail, well controlled noise and good dynamic range. The 5DS is now the benchmark for full-frame image quality, but it's not quite perfect. There's no Wi-Fi or Ultra HD video recording, and huge image file sizes necessitate decent memory cards and a fast computer.
Read the full review: Canon EOS 5DS
4. Nikon D750
A full frame DSLR packed with features for a reasonable price? Yes please
Sensor: Full-frame CMOS | Megapixels: 24.3MP | Autofocus: 51-point AF, 15 cross-type | Screen type: 3.2-inch tilting, 1,228,800 dots | Maximum continuous shooting speed: 6.5fps | Movies: 1080p | User level: Enthusiast/expert
Can't quite stretch to one of our top three options? The D750 still packs a cracking 24.3MP sensor and is as weatherproof as the D810, yet it's roughly 25% cheaper. Compared to its baby brother, the D610, the D750 has superior AF, metering and video systems, as well as a wider sensitivity range. Its continuous shooting speed isn't quite as fast as some may have hoped for, whilst the HDR and other special effect modes have limited use. But on the plus side, you do get a useful tilting screen and Wi-Fi connectivity. The D750 is a well-rounded, well-priced choice for enthusiasts.
Read the full review: Nikon D750
5. Nikon D5
Nikon's flagship DSLR has the best AF we've ever seen
Sensor: Full-frame CMOS | Megapixels: 20.8MP | Autofocus: 173-point AF, 99 cross-type | Screen type: 3.2-inch, 2,359,000 dots | Maximum continuous shooting speed: 12fps | Movies: 4K | User level: Expert
The D5 is Nikon's latest flagship DSLR, and it certainly doesn't disappoint. 20.8 megapixels might seem a bit stingy, but it means the D5 can shoot at 12fps continuous shooting, while the extended ISO range of ISO 3,280,000 has never been seen before. That's even before we get to the autofocus system - with a coverage of 173 AF points (99 of which are cross-type), the sophistication and speed of the AF is staggering. The ability to shoot 4K video is restricted to three minutes however, but that aside the D5 is a phenomenal camera.
Read the full review: Nikon D5
6. Canon EOS-1D X Mark II
Canon's latest top-flight DSLR is a speed machine
Sensor: Full-frame CMOS | Megapixels: 20.2MP | Autofocus: 61-point AF, 41 cross-type | Screen type: 3.2-inch, 1,620,000 dots | Maximum continuous shooting speed: 14fps | Movies: 4K | User level: Expert
Choosing between the 1D X Mark II and Nikon D5 will most likely depend on which manufacturer you're already tied to with your lens system, but the two cameras are otherwise closely matched. With EOS-1D X Mk II Canon has created a powerful and versatile camera that's a great choice for professional sport and news photographers. It doesn't have the outrageous sensitivity range of the Nikon D5, but it's very capable in low light, delivering excellent images within its standard sensitivity range.
Read the full review: Canon EOS-1D X Mark II
7. Pentax K-1
Pentax's first full-frame DSLR
Sensor: Full-frame CMOS | Megapixels: 36MP | Autofocus: 33-point AF, 25 cross-type | Screen type: 3.2-inch tilting, 1,037,000 dots | Maximum continuous shooting speed: 4.4fps | Movies: 1080p | User level: Enthusiast/expert
The K-1 offers a rugged build and a full-frame sensor at a relatively affordable price. It's not cheap, but it compares favourably with the likes of the Nikon D810, Canon 5D Mk III and Sony Alpha 7R II. Pentax's Pixel Shift Technology is clever, and it's great that the company has managed to produce a mode that can be used when the camera is hand-held, although the impact is subtle. Less of an all-rounder than the 5D Mk III, the K-1 makes an excellent camera for landscape, still life and portrait photography, or any genre that doesn't require fast autofocus and which benefits from a high pixel count for detail resolution.
Read the full review: Pentax K-1
8. Nikon D610
Looking to step up to a full-frame DSLR? Nikon has the camera for you
Sensor: Full-frame CMOS | Megapixels: 24.3MP | Autofocus: 39-point AF, 9 cross-type | Screen type: 3.2-inch, 921,000 dots | Maximum continuous shooting speed: 6fps | Movies: 1080p | User level: Enthusiast/expert
The D750 is good value, but the D610 gets you full-frame for even less. It's only an incremental upgrade over the preceding D600, but it addresses that camera's issues and boasts top-notch image and build quality. Although its pixel count is the same as the cheaper D7100, the increased sensor size results in greater dynamic range and less image noise. Full-frame is the name of the game, so extra features like Wi-Fi or a tilting screen are absent, but the 39-point AF system is reliable and the 6fps continuous shooting speed respectable. The D610 is slightly overshadowed by the newer D750, but it's still an excellent camera.
Read the full review: Nikon D610
9. Canon EOS 6D
Canon's most affordable full-frame DSLR punches above its weight
Sensor: Full-frame CMOS | Megapixels: 20.2MP | Autofocus: 11-point AF, 1 cross-type | Screen type: 3-inch, 1,040,000 dots | Maximum continuous shooting speed: 4.5fps | Movies: 1080p | User level: Enthusiast/expert
The 6D is Canon's answer to the D610 and is the least expensive model in the company's full-frame DSLR range. Its 20.2-megapixel sensor may sound outclassed, but there are hidden depths. Image quality is superb and photos impress with a three-dimensional feel that's the result of the larger sensor's ability to create shallow depth of field effects. However, the 6D's real trump card is price. It's one of the cheapest routes to a new full-frame DSLR, and though its autofocus system and continuous shooting speed are nothing special, you do get integrated Wi-Fi and GPS. If you can do without a built-in flash, the 6D is decent value.
Read the full review: Canon EOS 6D
10. Nikon Df
Nikon goes back to the future with this beautifully retro style statement
Sensor: Full-frame CMOS | Megapixels: 16.2MP | Autofocus: 39-point AF, 9 cross-type | Screen type: 3.2-inch, 921,000 dots | Maximum continuous shooting speed: 5.5fps | Movies: N/A | User level: Enthusiast/expert
Given the Df is arguably the most stylish new full-frame DSLR available, you might be surprised it's this far down our list. Well, that's not due to its looks, which are designed to emulate Nikon's classic FM-series 35mm film SLRs. The retro styling also extends to an extensive array of traditional controls, whilst the surprisingly compact weatherproof body adds further appeal. But despite great low light performance, the sensor's 16.2-megapixel resolution is now hard to justify next to more pixel-packed rivals, and the Df wont record video. Don't expect these drawbacks to keep the price down, either, as style doesn't come cheap.
Read the full review: Nikon Df