Best full-frame DSLR: 8 cameras from Canon, Nikon and Sony compared
28th Feb 2013 | 08:00
Top pro and consumer models rated
Full-frame DSLRs on test
Exciting times! Canon, Nikon and Sony all have new full-frame DSLRs that aren't aimed solely at professional or deep-pocketed amateur photographers. Indeed, the Nikon D600 is the first ever full-frame digital SLR to grace Nikon's consumer stable, while the Canon 6D shaves a huge amount off the price of the semi-pro Canon 5D Mark III.
Sony has gone full-frame with its DSLT (Single-Lens Translucent) range, while the Canon 1D X and Nikon D4 build on a rich, fully pro heritage. There's something for everyone, but what's so good about full-frame?
Most consumer class cameras, plus a few professional bodies, use APS-C image sensors. These measure about 25 x 17mm, around the same as a frame of antiquated Advanced Photographic System film with the classic APS-C framing.
A full-frame sensor is larger, at 36 x 24mm - the same size as a frame of regular 35mm film.
Historically, physically larger image sensors lent one of two advantages. Firstly, the greater surface area of the sensor could be packed with more pixels, delivering higher-resolution images. This has always been popular for portrait, fashion and landscape photography, because there's the potential for greater detail.
However, an alternative philosophy was to avoid increasing the pixel count, and to make the individual photo sites larger. This gives each pixel a greater light-gathering potential, helping to reduce image noise even in dull conditions.
Quick, quick, slow
It's not just about noise. Historically, high-resolution bodies were snapped up by portrait and landscape photographers, while relatively low-res models were more suited to action sports shooters.
For example, the Nikon D3x offers 24.5MP resolution but only a 5fps (frames per second) continuous shooting rate, whereas the Nikon D3s gives 12.1MP resolution but 9fps shooting. Similarly, the Canon EOS 1D Mark III delivers less than half the pixel count of the Canon EOS 1Ds Mark III, but doubles the maximum drive speed.
The new pro Canon EOS-1D X and Nikon D4 hedge their bets, opting for middling pixel counts of 18.1MP and 16.2MP, and maximum drive rates of 11fps and 12fps. The Canon can reach 14fps if you don't mind autofocus and metering being locked straight before the first frame in a sequence.
The Nikon D800 wins out overall with a monstrous 36.3MP, and the Sony a99 (as well as the cheaper Nikon D600) isn't far behind, at 24.3MP. The Sony still manages a fast drive rate of 8fps, or 10fps in max-speed mode, helped by its fixed, translucent mirror that doesn't need to flip up for each exposure.
In the shallows
Arguably the biggest advantage of full-frame cameras is that they enable a shallower depth of field than APS-C bodies. That's vital for portrait and still-life photographers, who want to blur backgrounds and keep the foreground subject sharp.
Crucially, depth of field is governed primarily by the actual focal length of the lens, rather than its effective focal length after the crop factor has been applied - typically 1.5x or 1.6x for APS-C based cameras.
Another bonus is that you can use top-quality lenses, which especially gives Canon and Nikon users a huge choice. Canon has never made any L-series (Luxury) lenses for APS-C format cameras.
Sure, there are benefits of using full-frame sized telephoto lenses on APS-C bodies, to effectively extend their reach. However, the crop factor destroys any wide-angle potential of lenses with short focal lengths.
And if you're going to pay top dollar for quality lenses that create a large enough image circle to cover a full-frame sensor, you might as well use all of it.
One final point is that the world often simply looks better through a full-frame camera. The viewfinder image is typically bigger and brighter, enabling a clearer view of what you're shooting. This makes for easier, more precise manual focusing whenever you want to take over control from the camera's autofocus system.
All of the cameras on test have high-quality pentaprism viewfinders, apart from the Sony a99. This camera uses an electronic viewfinder (EVF), which is necessitated by its fixed, translucent mirror design. It has its pros and cons, as you'll see.
None of the cameras here keep things simple. Instead, they're powerful bodies to suit advanced, creative photographers.
However, the biggest, most professional cameras go further still, generally sprouting more buttons for direct access to shooting parameters than most people have fingers to press them.
The big boys also have duplicated shutter buttons and command dials for comfortable shooting in portrait orientation.
Now, let's crack on with a closer look at all the cameras in detail, starting with the least expensive at current market prices.
Price: £1,450/US$2,000/AU$2,380 (body only)
Specs: 24.3MP, Full HD video: 1080p, 39-point AF, ISO 50-25600
The Nikon D600 certainly doesn't qualify as a cheap camera, but it's currently the least expensive full-frame body on the market. At a glance, it looks almost identical to the Nikon D7000 but, on closer inspection, the layout of the control buttons is a little different and the D600 is slightly larger.
Its physical size is a close match for the Canon 6D, both cameras being diminutive for full-frame cameras.
Build quality feels consumer-class rather than fully professional. The body is a mix of magnesium alloy and polycarbonate, the latter material being used for the front of the camera, into which the metal lens mount is fitted. This isn't quite ideal, but there shouldn't be any issues taking the strain of big, heavy full-frame lenses.
Nikon is keen to point out that the D600 has the same level of weather-proofing as the pro-class D800.
Further similarities between the Nikon D600 and D7000 are that they both feature fairly new 2,016-pixel RGB metering sensors and 39-point Multi-CAM 4800 autofocus modules. The number of AF points here is much more generous than the Canon EOS 6D's 11 points.
However, compared with the Nikon D7000, all of the D600's AF points are much more tightly packed around the centre of the frame. It's quite similar to the Sony a99 in this respect.
The Nikon D600 makes the most of its 24.3MP resolution and Expeed 3 image processor. These combine to deliver high-resolution images with a respectable maximum continuous drive rate of 5.5fps. That figure is considerably faster than the D800's pedestrian 4fps. Images are noticeably sharper when viewed straight out of the camera than with the D7000, marking a further distinction between the D600 and Nikon's similar APS-C body.
Metering is fully consistent and autofocus is assured. When using the same lenses, autofocus is a little more accurate than with the D7000, although it can be a bit ponderous in near-dark conditions, where the 6D works slightly better.
Like most entry-level and mid-range Nikon cameras, the D600 produces particularly punchy images, with plenty of saturation.
Full ISO 200 image, see the cropped (100%) version below
The 24.3MP Nikon D600 edges ahead of all the Canon cameras, especially in the sensitivity range between ISO 100 and ISO 1600.
Noise starts to creep in at ISO 3200, but the Nikon D600 produces very finely detailed images at high sensitivity settings.
The Nikon D600 scores quite well for colour accuracy, but green hues can be strident and saturation is often boosted.
Image test verdict
Results are punchy, with bags of contrast and saturation, but noise is more noticeable than from most competing cameras at high ISO settings.
Read our Nikon D600 review
Price: £1,600/US$2,100/AU$2,300 (body only)
Specs: 20.2MP, Full HD video: 1080p, 11-point AF, ISO 50-102400, Wi-Fi, GPS
Canon's answer to the Nikon D600 comes in the similarly compact shape of the Canon EOS 6D. And while there's almost no difference in their physical sizes, the Canon is nearly 100g lighter in weight. One reason for this is that the Canon 6D's top plate is polycarbonate, but at least the front and back sections of the body are sturdier magnesium alloy.
Overall build quality of the camera feels on a par with the Nikon D600. Indeed, whereas the D600 feels rather like the full-frame equivalent of the D7000, the Canon EOS 6D feels like the full-frame 60D. As such, it's a real shame that Canon omitted the pivoting LCD that's so popular on the 60D. At least there's an AF fine-tune facility, which is lacking on the 60D.
Another glaring omission for a 'consumer' class camera is that the Canon 6D has no pop-up flash. Serious photographers often dismiss pop-up flash, due to their inferior power and quality, but we think they can still be useful for fill-flash, as well as for easy wireless command of more effective off-camera flashguns.
Another slight disappointment is that the 6D is the only camera in this group in which the viewfinder doesn't give full 100% frame coverage, and it only has a single memory card slot.
The 6D boasts built-in GPS and can automatically geo-tag images. When enabled, however, the GPS remains active even when the camera is switched off, and can drain a fully charged battery in just a couple of days, without the camera ever even being turned on.
Better news, though, is the camera's built-in Wi-Fi, which enables you to shoot remotely and wirelessly via a compatible computer, tablet or smart phone.
Resolution is respectable enough at 20.2MP, but the 6D loses out slightly to the Nikon D600's 24.3MP, while also giving a reduced maximum burst rate of 4.5fps instead of 5.5fps. The camera's autofocus works well even under very dull lighting but, again, the provision of 11 AF points is less than generous, and only the central AF point is cross-type.
Natural-looking results are assured, but landscape colours can be a bit muted compared with the other Canon cameras.
The 6D holds its own against most of the competition, giving similarly impressive resolution throughout its standard sensitivity range.
Impressively noise-free at very high ISO settings, aggressive levels of smoothing only start to become evident at ISO 6400.
The Canon EOS 6D tends to warm up cooler scenes, but the end results generally look great.
Image test verdict
Very good image quality is maintained even at high ISO settings, but you may want to increase the saturation of landscape images.
Read the Canon 6D review
Price: £1,900/US$2,800/AU$3,380 (body only)
Specs: 36.3MP, Full HD video: 1080p, 51-point AF, ISO 50-25600
Weighing in at exactly a kilo, the Nikon D800 is about a third heavier than the Canon 6D and feels more robust than the slightly smaller D600. Classed as a professional body, it has a tough magnesium alloy build and controls that will be instantly familiar to users of Nikon's more upmarket cameras.
These include dedicated buttons for image quality, bracketing, ISO and white balance, all built into the top of the drive mode dial.
Unlike the D3x and D4, though, the Nikon D800 retains a pop-up flash, with versatile controls for use as a wireless commander with remote flashguns. Also unlike the more exotic D3x and D4, there are no duplicated shooting buttons for comfortable portrait-orientation shooting, but this gives the advantage of a more compact, lightweight build.
There's plenty of crystal clarity from the class-leading 36.3MP sensor, with an Expeed 3 image processor. Coupled with a top-quality lens, the Nikon D800 can produce extraordinary levels of detail.
Naturally, the potential drawbacks of ultra-high resolution sensors are an increase in image noise and a decrease in dynamic range, but the D800 scores fairly well in both areas. Even so, there's no getting around the increased data size of its very high-resolution images. Continuous drive mode is sluggish, with a maximum rate of just 4fps.
Autofocus is super-fast and unerringly accurate, based on the same 51-point AF sensor that's fitted to the Nikon D4. This includes 15 cross-type points, which really come into their own for focusing on tricky targets or in very low light conditions.
As with the other Nikon cameras on test, metering is uncannily accurate even in difficult conditions, and works very well with Active D-Lighting for taming high-contrast scenes.
A little less exuberant than the Nikon D600, contrast and colour rendition tend towards accuracy rather than punchiness on the Nikon D800.
Thanks in part to its 36.3MP sensor, the D800 reigns supreme in the resolution stakes, claiming the highest scores in the group.
Image noise is slightly more visible in the Nikon D800's images than in the D600's at ISO 3200, while retention of fine detail isn't quite as good.
Very good overall, accuracy is impressive and saturation tends to be a little more modest and natural than with the D600.
Image test verdict
A good compromise between natural and punchy images, the D800 delivers pleasing results. There's certainly no lack of image resolution.
Read our Nikon D800 review
Sony Alpha a99
Price: £2,200/US$2,800/AU$2,800 (body only)
Specs: 24.3MP, Full HD video: 1080p, 102-point AF, ISO 100-25600, GPS
Different by design, the Sony Alpha a99 is the only camera in this group that doesn't feature a conventional, flip-up reflex mirror inside. Instead, it has a translucent mirror that remains fixed in place, enabling 70% of the light to pass through to the image sensor, while reflecting 30% upwards into a phase-detection autofocus sensor.
The camera's viewfinder is also fundamentally different to any of the other cameras on test. Because of the relatively small amount of light that's directed upwards from the translucent mirror, the Sony a99 relies on an EVF (electronic viewfinder).
These can be notoriously low in resolution and jerky when panning, but the unit on the a99 is a top-quality OLED display with a very high 2.36MP resolution and 100% frame coverage. It's easy on the eye, great at boosting brightness in near-dark shooting conditions and gives the advantage of showing you optional extra shooting information, such as a full-time virtual horizon or a live histogram, to help composition.
Other unusual features here are built-in sensor-shift stabilisation, a GPS for optional geo-tags and an articulated rear LCD. Sensibly, and unlike with the Canon EOS 6D, the GPS turns off automatically when you switch off the camera, extending your battery life.
Build quality is sturdy and there are plenty of direct-access buttons for clever tricks such as an autofocus range limiter (complete with a clear on-screen display).
However, overall handling isn't as slick or assured as with competing Canon and Nikon bodies. The maximum drive rate is a useful 6fps (10fps in crop mode).
Metering can be a bit on the dark side in anything other than bright sunlight, and autofocus is moveable. Even with a fast lens, the Sony a99 struggles to autofocus in low light, strangely being less competent than the APS-C based Sony a77 camera. There are 19 selectable autofocus points available, of which 11 are cross-type. However, like with the Nikon D600, they're all uncomfortably close to the centre of the frame.
Contrast can be a little lacking, and the Sony a99 typically produces darker images than competing cameras, apart from under bright sunlight.
The a99 is extremely consistent in resolution, returning the same high score from ISO 50-3200, and only really dropping off at ISO 25600.
Performance is good at lower sensitivities through to ISO 3200, but image noise ramps up noticeably from ISO 6400 onwards.
From direct sunlight to cloudy and shady conditions, colour balance from the Sony a99 is quite accurate with a hint of warmth.
Image test verdict
Images can often look a little dark and can lack contrast, but colour rendition is good and noise is low unless you use ultra-high sensitivity settings.
Read our Sony Alpha a99 review
Canon 5D Mark III
Price: £2,340/US$3,500/AU$3,600 (body only)
Specs: 22.3MP, Full HD video: 1080p, 61-point AF, ISO 50-102400
Back in 2005, the original Canon 5D brought full-frame digital photography to the masses. Two generations later, the Canon EOS 5D Mark III brings Canon's latest round of refinements to the mid-price DSLR sector. Like the Canon 6D and Canon 1D X, it boasts Digic 5+ image processing, although the upmarket 1D X has two processors rather than one.
The pixel count is marginally higher than the preceding 5D Mark II, at 22.3MP instead of 21.1MP. But, despite this, the maximum drive rate gets a hefty boost from 3.9fps to 6fps.
Further improvements over the Mark II include a more generous sensitivity range, stretching to ISO 25600 instead of ISO 6400 in the standard range. And whereas the Mark II only had a nine-point autofocus system, the Mark III boasts a 61-point AF system with 41 cross-type points, in common with the mighty Canon EOS-1D X.
Direct-access controls here are more wide-ranging than in the EOS 6D and, whereas the EOS 6D only has a single SD/HC/XC memory card slot, the EOS 5D Mark III has dual slots for both SD/HC/XC and CompactFlash.
The Canon EOS 5D Mark III is also better built than the Mark II, with a full magnesium alloy body that feels more tough and rugged, being similar in size and weight to the Nikon D800.
Metering on the Canon EOS 5D Mark III is very accurate but, as with other current Canon DSLRs, it's based on the company's iFCL (intelligent Focus Colour Luminance) system. It's massively biased to the active AF point, which is good for capturing tricky shots such as backlit portraits. In general shooting, however, the centre-weighted metering mode can be more predictable.
HDR shooting modes are quickly becoming more common, but the implementation is particularly good on the Canon 5D Mark III. All the source shots are saved, as well as the merged image.
Autofocus performance and image quality are very impressive in low-light conditions. Fine details are retained well and there's excellent control over noise, even at high ISOs.
Results are very similar to the mighty Canon EOS-1D X, with very smooth tonal graduations and a natural look to the colour balance.
Very good overall, the Canon EOS 5D Mark III's resolution only really drops off at ISO 25600 and into the expanded sensitivity range.
Image noise is slightly more noticeable than with the Canon EOS 6D at very high ISO settings, but retention of fine detail is better.
There's very little to choose between in terms of colour rendition from this camera and from the Canon EOS 6D. They're both very natural, if warm.
Image test verdict
Excellent image quality is assured in all sorts of lighting conditions, with results generally being almost as superb as from the 1D X.
Read our Canon 5D Mark III review
Price: £5,000/US$6,700 (around AU$7,385) (body only)
Specs: 24.5MP, 51-point AF, ISO 100-6400
Professional cameras don't get updated as often as their consumer-based counterparts. Even so, four years is a long innings, and the Nikon D3x is showing its age. Originally launched as a high-res version of the D3, this camera's headline attraction was its 24.5MP sensor. That no longer looks so special, compared with the new Nikon D600 and Nikon D800, although it's still higher than the Nikon D4's 16.2MP.
A crucial difference between the D3x and newer cameras is that its high resolution comes at the price of a relatively meagre sensitivity range. For example, the D600 and D800 offer standard ranges of ISO 100-6400, boosted to an equivalent of ISO 25600 in expanded mode. The D3x only manages ISO 100-1600 in standard trim, and its maximum expanded setting is just ISO 6400.
Another trade-off of the high resolution is the modest maximum drive rate of 5fps. Further signs of ageing include a complete lack of video capture capabilities, and only a rudimentary Live View tool.
Image processing is courtesy of the first generation of Expeed processor, whereas all the other Nikon cameras in this group use Expeed 3.
In the hand, the Nikon D3x really does feel like the consummate professional camera. Handling is superb, and it's reassuringly robust. Autofocus and metering performance is highly competent, too.
In good lighting conditions, it delivers fabulous image quality, so it still has a lot to offer for pro landscape and studio portrait photographers. The latter will benefit from comfortable, duplicated controls for portrait-orientation shooting.
However, the camera's image quality is disappointing at high ISO settings, where noise is all too noticeable. Couple this with the lack of video capture, and it's clear that the D3x has been overtaken by its competitors. Nikon shooters who want ultra-high resolution images will be tempted to take a step down in build quality and fully pro handling (not to mention purchase price) and go for a D800 instead.
Scenic shots are highly detailed, with good contrast. Colour rendition tends to be slightly warmer in the Nikon D3x's images than in the D4's.
Built as a high-res professional camera, the D3x delivers on its promise, especially towards the bottom of its ISO range.
Noise is very much more noticeable in the D3x's images taken at high ISO settings than it is with any other full-frame camera in the group.
There's generally a nice warmth to this camera's colour balance, but it can go a bit too far when shooting in very bright sunlight.
Image test verdict
Image quality suffers at high ISO settings, but at lower ISOs there's plenty of detail, along with negligible noise and a warmth in colour rendition.
Read our Nikon D3x review
Price: £4,250/US$6,000/AU$6,700 (body only)
Specs: 16.2MP, Full HD video: 1080p, 51-point AF, ISO 200-204800
Following in the footsteps of the Nikon D3 and Nikon D3s, the Nikon D4 offers a significant but not an overblown increase in resolution, from 12.1MP to 16.2MP. Coupled with the latest-generation Expeed 3 image processor, the aim is to deliver a fast 11fps maximum drive rate with excellent image quality, even at very high sensitivity settings. That's all very well, but the D4 is the lowest-pixel count camera on test.
For sensitivity, the D4 beats all other Nikon cameras in this group, with ISO 100-12800 in its standard range, rising to a maximum expanded equivalent of ISO 204800. Even so, standard-range sensitivity is eclipsed by all of the Canon cameras in this article, as well as by the Sony Alpha a99.
The Nikon D4's chunky, fully-pro build includes all the usual extras, such as duplicated controls for portrait-orientation shooting and an extra info screen around the back.
Build quality is of battleship standards. Tough and weather-proofed on the outside, the Nikon D4 also includes a new Kevlar/carbon-fibre shutter unit with a life expectancy of 400,000 cycles (30% up on the Nikon D3x). The only slight frustration is its somewhat rattly memory card door.
There's a new 3D Colour Matrix III metering module, complete with full-time face recognition, along with 51-point autofocus. Handy for sports and wildlife photographers, the 15 cross-type points can be used with lenses and teleconverters that have a maximum aperture of f/8. However, both updated metering and autofocus systems also feature on the Nikon D800.
True to its promise, the Nikon D4 delivers super-smooth yet detailed image quality even at very high ISO settings, putting the D3x to shame. There's plenty of vibrancy but the D4 errs on the side of caution, resisting the temptation to bump up saturation in the way that some Nikon cameras do.
Performance is excellent in all areas, and the D4 works brilliantly in practically all shooting conditions. It's a sign of the times, though, that a resolution of 16.2MP can leave you feeling a little short-changed.
There's superb consistency in metering and white balance. Like with the other Nikon cameras, colour balance is quite warm in bright sun.
Despite having the lowest pixel count sensor in the group, the Nikon D4 keeps up with the Canon cameras, at least through low and medium ISOs.
Noise suppression is slightly better even than from the Canon EOS-1D X at ISO 3200, but it's not quite as impressive at ISO 6400.
The most natural of all the Nikon cameras in the group, there's not much difference between the D4 and the Canon EOS-1D X.
Image test verdict
Fabulous image quality is one of the hallmarks of the Nikon D4. What it lacks in pixel count, it makes up for in sharpness and low-noise performance.
Read our Nikon D4 review
Canon 1D X
Price: £4,850/US$6,800/AU$7,300 (body only)
Specs: 18.1MP, Full HD video: 1080p, 61-point AFT, ISO 100-204800
Following a similar design philosophy to the Nikon D4, the Canon EOS-1D X restrains resolution to help ensure fast drive rates and super-clean image quality at higher ISO settings. The former is assisted by dual Digic 5+ image processors, delivering a class-leading 12fps burst rate, boosted to 14fps if the autofocus and metering are disabled after the first shot taken in a rapid-fire sequence.
The Canon EOS-1D X also wins out in the ISO stakes, with a massive top setting of ISO 51200 available in its standard range, and up to a huge ISO 204800 in expanded mode. And all of this is available with nearly two extra megapixels under the bonnet, compared with the Nikon D4.
As you'd expect from a fully pro body, there are weather seals aplenty here, and the overall build quality feels pretty much bomb-proof. A little more conservative than the Nikon D4, dual memory slots are both CompactFlash format, instead of mixing in an XQD for novelty value. How well and how quickly the XQD format takes off remains to be seen.
Other finery includes the same 61-point autofocus system seen on Canon's 5D Mark III, which copes well with tracking fast-moving objects. For continuous shooting, the increased buffer size can accommodate 38 raw files rather than the 5D Mark III's 18 files. It's a good thing, considering that the maximum drive rate is twice as fast, too.
The handling of the full-frame Canon EOS-1D X is sublime. The duplicated shooting controls, along with dual multi-controllers and centralised quick-control dial, make the camera feel equally natural in landscape- and portrait-orientation shooting.
Image quality is stunning straight out of the camera. There's an abundance of fine detail and negligible image noise, even at ISO 6400.
When shooting on overcast days, or in the shade, the colour balance from the Canon EOS-1D X tends to come off slightly warmer than from the Nikon D4. This looks generally pleasant and is particularly flattering for portraiture shots.
Metering and autofocus are very accurate here. Fine detail is well preserved, while colour and contrast in outdoor images are excellent.
Despite a slightly lower pixel count, scores are a close match for the Canon 6D and Canon 5D Mark III throughout the whole ISO range.
Extremely well suppressed even at ISO 6400, noise is essentially a non-issue, while texture and fine detail are particularly well preserved.
Compared with the other Canon cameras on test, the 1D X generates a little extra warmth when lighting conditions are cloudy or shady.
Image test verdict
Composition aside, it's almost impossible to take a bad shot with the 1D X. It reacts superbly to even challenging lighting conditions and scenic content.
Read our Canon 1D X review
Verdict: best full-frame DSLR
The Nikon D3x was a very impressive full-frame DSLR when it was first announced, but it can't really compete in our lab tests against its more modern rivals.
The difference between its signal-to-noise ratio and dynamic range scores reflects the technological developments that have taken place since December 2008, when it was originally released.
The Nikon D600 and Nikon D4 produce particularly impressive results at the lower sensitivity values, but it seems that Canon has tried to achieve a more consistent performance across the entire sensitivity range with its cameras.
Not surprisingly, given its huge pixel count, the Nikon D800's signal-to-noise ratio and dynamic range scores take the most dramatic dip at ISO 160 and above.
Spend £4,850/US$6,800/AU$7,300 on a camera body and you expect something special. The Canon 1D X has "special" written all over it. Handling, image quality and build quality are all superlative.
The 18.1MP resolution and dual Digic 5+ image processors deliver a class-leading drive rate of up to 14fps, along with spectacular low-noise performance even at very high ISO settings. This makes it our top full-frame DSLR.
However, the Nikon D4 runs a very close second, and at £4,250/US$6,000/AU$6,700 is cheaper to buy. Both cameras are excellent all-rounders, even if they don't rule the roost when it comes to image resolution in this test.
If you want ultra-high resolution, the 36.3MP Nikon D800 is a natural choice, but you'll need the very finest lenses to do full justice to those extra megapixels. The older D3x is past its best, and has relatively poor high-ISO performance.
The most affordable full-frame cameras are the Canon 6D and Nikon D600. We prefer the D600, with full-coverage viewfinder, more advanced autofocus, pop-up flash with wireless command options, and dual memory slots, even if it lacks the 6D's built-in Wi-Fi and GPS.