A7R, S, II, or III? Making sense of Sony’s full-frame mirrorless cameras

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Sony has proven itself a leader in mirrorless interchangeable lens cameras with its full-frame A-series cameras, but when it comes to buying one, things can be a bit confusing. In the current lineup, the A9, A7 III, A7R III, and A7S II are all capable models, but each has unique advantages that may make it better or worse in any given situation.

The most obvious difference in these cameras is the sensor resolution, which varies considerably from the A7R III’s 42 megapixels (one of the highest-megapixel full-frame sensors you can currently buy) down to the A7S II’s 12 megapixels. The A9 and A7 III take up the middle spots with 24 megapixels.

The numbers alone may lead one to think the A7S II is the entry-level model, but this is not the case. It is actually the A7 III, at $2,000, that holds down the low end of the range (although, “low end” is probably an inaccurate description here). The A7S II is a niche camera — and the only A7-series model to not receive a third-generation update yet — that targets professional photographers and filmmakers who work in low light, and its $2,700 price tag reflects this. The A7R III tops the range at $3,200, while the A9 is a different beast altogether, coming in at $4,500. (All prices listed are for the camera body without a lens, and no take take into account any current rebates.)

But just because one camera costs more than the other doesn’t necessarily make it better. But each also has its strengths and weaknesses, and which one will work best for you depends on what you plan to shoot, so let’s take a closer look at each.

Sony A9

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Adam Balkin/Digital Trends
Adam Balkin/Digital Trends

If it’s speed and precision you need, it’s the A9 you want. Sony’s flagship mirrorless camera uses a newly developed full-frame Exmor RS backside illuminated (BSI) CMOS sensor. It’s paired up with a new Bionz X image processor for better performance across the board. 

Its stacked sensor measures in at only 24 megapixels, but what it lacks in resolution, it makes up for in speed. The A9 shoots up to 20 fps RAW continuously when used with a UHS-II SDXC card for the required write speeds. Compared to the 14 fps of Canon’s 1D-X Mark II and 12 FPS of Nikon’s D5, it’s nothing short of mesmerizing. 

The sensor also has an extended ISO range of 50 to 204,800 and can fire its electronic shutter speed at 1/32,000 of a second, a fast enough speed that rolling shutter is much less of a concern than with other electronic shutter systems.

Its autofocus system consists of 693 phase-detection AF points and 25 contrast-detection points. In total, the autofocus points cover more than 93 percent of the frame, with calculations being made up to 60 times per second — more than enough for even the most demanding environments and subjects. 

Although the 24MP sensor grabs much of the attention, you’d be remiss to overlook the 3,686k-dot OLED electronic viewfinder that offers a no-blackout display when shooting bursts. With DSLRs, the mirror needs to flip up to capture an exposure, causing momentary viewfinder blackout, even when shooting at the fastest continuous speed. With the electronic shutter, the A9 makes blackouts a thing of the past, meaning the entire time you’re holding down the shutter and taking photos, you’re still seeing a live view of exactly what the sensor is seeing, even at 20 fps.

It’s not just stills the A9 excels at, either. It shoots 4K video at 30 fps at 100Mbps with full readout and no pixel binning.

In addition to its impressive sensor and autofocus capabilities, the A9 is also weather-sealed (dust and moisture resistant), includes dual SD card slots, and features both wired (Ethernet) and wireless (Wi-Fi, NFC, and Bluetooth) connectivity. 

Sony wasn’t playing games when it launched the A9. It wanted to take DSLRs head on. And from the looks of it, they’ve managed to do just that. Of course, with DSLR-level specs comes DSLR pricing. At $4,500 for the body alone, it’s not exactly a consumer-centered camera. Thankfully, many of the technologies from the A9 have trickled down into other third-generation Sony full-frame mirrorless cameras, such as the A7 III.

Our first take review

Sony A7 III

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Sony might call the A7 III “the basic model” of its lineup, but it’s far from basic in our book. Its 24MP backside illuminated sensor brings along improved low-light performance and increased dynamic range compared to its already-capable predecessor, the A7 II. It also strikes a good balance between file size and resolution. It won’t quite match the detail of the A7R II or the extreme low-light capabilities of the A7S II, but for most situations, it will perform admirably.

The A7 III boasts the same 693-point autofocus system found inside the flagship A9, and AF performance is equally quick and reliable. Battery life is doubled compared the previous generation, at 710 shots per charge, putting it well into DSLR territory.

As with other third-generation A-series cameras from Sony, the A7 III now has a burst rate of 10 fps. In full continuous mode, it can shoot 177 JPEGs before the buffer gets filled, and although the specifics of RAW buffer size haven’t been mentioned, it’s safe to assume it’s a good bit lower. Compared to the A9, sports camera this is not, but it is considerably faster than other entry-level full-frame cameras.

To make up for the lack of 4K in its predecessor, the A7 III stands strong in its video capabilities. It shoots 4K video by oversampling 6K footage from the full width of the sensor. Like the A9, there’s no line skipping or pixel binning, so footage should come out sharp. Thanks to S-Log flat color profiles, video preserves 14 stops of dynamic range and should be ready for advanced color grading.

As the specs show, the A7 III is anything but basic. From a value standpoint, it is likely the best camera on this list. Even if your budget is $3,000, getting the A7 III will leave you room for at least one nice lens, and the lens will make the most noticeable difference in image quality.

Sony A7R III

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The A7R III is a high-resolution force to be reckoned with. It uses a 42MP, backside-illuminated (BSI) CMOS sensor, which means all the little electrical bits that normally run along the front of the sensor have been moved to the back. Although the sensor inside is the same one found in its predecessor, other new electronics have helped to squeeze more out of it — most notably, an extra stop of dynamic range (now at 15 stops). The stabilization system has also been improved, now offering a claimed 5.5 stops of shake reduction.

Having all those pixels means that, with a good lens and — preferably — mounted on a tripod, this camera can deliver stunning levels of detail like few other full-frame cameras. Especially when using its all new Pixel-Shift Multi Shooting mode. When mounted on a tripod, the A7R III can move the sensor one pixel in multiple directions to capture a whopping 169.6MP image. As of now, the final image must be processed on a computer, not in-camera, but it’s still an impressive feat.

When it comes to autofocus, the A7R III is slightly behind the newer A9, but it is certainly no slouch. It uses 399 phase-detection points and 425 contrast detection points. The phase detection points remain unchanged from the A7R II, but the contrast detection points received a dramatic increase from the 25 found in its predecessor. Together, the autofocus points cover 68 percent of the frame and are said to increase autofocus performance twofold compared to the A7R II.

Also improved is the burst capability. The A7R III maxes out at 10 fps in burst mode, although RAW files go from 14-bit to 12-bit when shooting at full speed. To help manage the increased image output, Sony has taken a page from the A9 and added dual memory card slots, one UHS-II and one UHS-I.

When it comes to video, the A7R III impresses again. It can shoot 4K either in full frame mode, or from a cropped, Super35mm-sized region of the sensor. In Super35 mode, which mimics the frame size of motion picture film, it overscans additional pixels for an extra-sharp 4K output. It also uses S-Log2, a flat gamma profile that captures the maximum dynamic range and is suitable for professional color grading.

One area Sony really improved on with the A7R III is the battery life, with a rating of 650 exposures per charge, just below that of the A7 III.

Working with the A7R III won’t be for everyone. It is meant for photographers who are willing to put in the time to get things right. But if that’s you, the A7R II promises perhaps the best possible image quality you can get, shy of top-of-the-line medium format systems.

Our hands-on review

Sony A7S II

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The A7S II is the only model that hasn’t yet been updated into the third generation. It is the most narrowly focused camera of the three A7-series models. With just 12 megapixels, it falls quite a ways behind the resolution of most current interchangeable lens cameras, even lower-end consumer models.

That low resolution, however, means each individual pixel is much larger and therefore more sensitive to light. Its ISO range can be expanded up to 409,600, so you can pretty much shoot under moonlight. It’s not the highest ISO rating out there (Nikon’s D5 pushes into the millions) but the A7S II’s large pixels help it maintain accurate color and dynamic range at its highest settings, meaning you’re shooting high ISO photos that you can actually use.

Clearly, this is a camera for those who need the ultimate in low-light performance. This includes cave explorers, night sky photographers, and some photojournalists.

The unintended benefit of the low-resolution sensor also means more pictures can be saved in the same amount of space and will transfer much faster to a computer. This will be a plus to anyone who comes back from a shoot with thousands of photos, as many event photographers do.

For video, the A7S II can also record beautiful 4K footage from the full sensor, although it doesn’t have enough resolution to shoot 4K from a Super35 crop, like the A7R II. It will, however, shoot 1080p in crop mode at up to 120 frames-per-second for slow motion. It also uses Sony’s latest log profile, S-Log3, providing the most flexibility in post-production.

If there is a sore point for this camera, however, it is the autofocus. Despite being the newest of the three, its 169-point AF system relies completely on older, slower contrast detection technology. It also can’t track moving subjects in continuous shooting mode, as the AF stays locked after the first frame.

Our full review

Previous generation Sony A7 cameras

While the focus of this story is on the latest cameras, we should note previous A-series cameras are still available for sale. What they lack in new features, they make up for in lower prices. The A7R II has the same high-resolution sensor as the new mark III model, while the A7S is a low-light champ just like its younger, second-generation sibling.

Again, however, the most attractive model could be the A7, this time the mark II. It won’t quite match the ISO performance or dynamic range of the A7 III, but it still uses a 24MP sensor capable of producing some brilliant images. For still photographers on a budget who want to move into full-frame, the $1,100 list price is also quite enticing. Getting a new-in-the-box full-frame camera for that price is simply unheard of from any other brand.

So while we all love the latest and greatest tech, you can save a lot of money by buying a model from the prior generation, money that go to lenses, flashes, or other accessories that may make a bigger difference in the quality of your images. If you don’t need the latest speed and features, the A7 II, A7R II, or A7S might be the right camera for you.

Sony A7 II review | Sony A7r II review | Sony A7s review

Conclusion

As similar as all of Sony’s latest-generation full-frame mirrorless cameras are, there are clear differences that define how they are best used. For the majority of shooters, the A7 III will deliver great image quality across a wide spectrum of scenarios, and it certainly doesn’t hurt that it starts at just two grand. For professionals, or anyone with the most discerning eyes, the A7R III simply can’t be beat. Likewise, when speed and performance are key, the A9 fills a niche gap for photographers who expect the most from their cameras.