Sony’s Full-Frame Mirrorless Lineup: Which a7/a9 is Right for You?

First came the trio of a7 cameras, then came the a7 II series, and now we have the a9. It doesn’t seem like there is any end in sight for Sony with its full-frame mirrorless lineup, and each one has its own unique capabilities. So, if you are looking to grab a member of Sony’s ever-expanding camera family, we are here to help you pick out the one that is best for you.

Overview

We are going to focus on the most current models—the a7 II series and the a9. If you are looking to save some cash or just don’t need/want the latest and greatest, then the original a7 cameras are still spectacular options and I highly recommend them. For the most part, the version I models follow the same basic principles as their successors, but if you want to dive deeper into the differences between them, you should check out our previous comparison of these cameras.

For an understanding of the variety of features, we need to talk about how Sony positions these cameras in the market. We may as well start at the top, with the newest of the bunch, the flagship Alpha a9. Focusing heavily on sports and action, the a9 is in direct competition with the Nikon D5 and Canon 1D X Mark II, both flagships themselves. This fits in with the camera industry as a whole, and makes sense, considering where it sits price-wise.

The next step down the ladder, though not too far down, is the specialized pair of the a7R II and a7S II. Each of these is classified as a professional option, though the extreme contrast in features means that while they are effectively equals, they are certainly not interchangeable. The a7R II appeals directly to photographers with its high-resolution and outstanding dynamic range, while the a7S II is a low-light monster that produces some of the best 4K footage available in this form factor. If you were looking for comparisons to other brands, I would have to say they are equivalent to the Canon 5D line and Nikon D800 series.

Finally, we come to one of the best values currently available: the a7 II. Sony places this more in the advanced amateur or semi-professional realm, which puts it on par with the Canon 6D Mark II and Nikon D750/D610. It offers stellar image quality and features, but it’s positioned as more of a generalist’s camera.

Image Quality

The first consideration in every camera comparison is always image quality. For this test, we are going to have to break it down into three separate sections to get the full picture on how these cameras differ. First, we will discuss detail and resolution; second, low-light performance and sensitivity; and third, a somewhat subjective analysis of dynamic range in a real-world test.

Resolution

This looks like it will be a very straightforward test, with 12MP, 24MP, and 42MP all different enough to provide an obvious answer. To perform this test, I took one of the sharpest lenses currently available for the system, the FE 90mm f/2.8 Macro G OSS, and photographed some colored pencils. I set all the cameras to ISO 100, stopped the lens down to f/8, and snapped the same image with each. All the raw files were then brought into Capture One Pro, where no adjustments were made, all lens corrections were turned off, and no noise reduction was applied.

Unsurprisingly, the a7R II takes the win here with its astounding 42MP sensor bringing out every little detail there possibly could be in the pencils. Coming in second are the a9 and a7 II, though if I need to pick one over the other, the a9’s latest processing seems to eke just a hair more detail out of the files, but not by much. Finally, we have the a7S II, which at just 12MP, is a far cry from the top. However, one thing to note about the a7S II is that when you get into higher ISOs it may be possible to glean more/better detail than noisier images from a higher-res camera, which may matter if you constantly find yourself cranking up the ISO.

Low-Light Performance

The next step on our journey is low-light performance, or how well the cameras handle noise at higher sensitivities. For this test I set up a single LED light on a still life with a black background for a subject. I used the FE 70-200mm f/4 G OSS at 70mm stopped down to f/5.6 and then dialed-in the appropriate shutter speed as we went up the ISO range. And, as before, all the images were brought into Capture One Pro, where I made sure that no corrections were being applied.

I started the test at ISO 1600 to keep this collection of images more reasonable and, if you are concerned with base ISO performance, you can look at the resolution test above. Check out the samples below for yourself.

Taken with the a7

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Taken with the a7r

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Taken with the a7S

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Taken with the a9

Looking at this, the most surprising thing to me is the performance of the a9, which holds its own against even the a7S II. The a7S II is unsurprisingly the winner, but not by as large a margin as one would expect, given its feature set. The a7R II may edge out the a9—since it has such high resolution, a lot of noise can be hidden when the images are viewed using similar sizes, but the a9 is impressive even at ISO 204800. The a7 II, on the other hand, falls exactly where you would expect, though it provides very good performance all the way up to its maximum of ISO 25600.

Real-World Dynamic Range

Keeping this test grounded in the real world, we had to look at dynamic range and the malleability of raw files in post. One of the most difficult tests for a camera must be when part of the scene is in bright sunlight and the other part is in dark shadow; that is why I chose to shoot under this bridge to see what I could do. I bracketed the exposure to get the best possible selection of files to work with and examine and found that everything looks really good regardless of which camera I used. The a7R II appears to have the most dynamic range from these files, and the a7 II seems to lose a little something in the highlights, with the a9 and a7S II falling somewhere in the middle.

If I had to rank the cameras, I would arrange them this way: a7R II > a9/a7S II > a7 II, though you really can’t go wrong with any of them. One thing I will note when directly comparing the a7R II, a7S II, and a9 is that this is going to be tied into low-light performance when it comes to higher ISOs. From experience, I can say that the a7S II maintains a notably better DR when shooting at higher sensitivities. I would expect the a9 and a7R II to remain evenly matched, but I would say that the a9 will likely overtake the a7R II when working at the uppermost limits of these cameras.

Performance

For the second stage of this comparison, we are looking at how well the cameras operate, including things like speed and features.

Autofocus and Speed

Perhaps the widest-ranging spec of these cameras is in the autofocus systems. We have everything from a revolutionary 693-point phase-detection system in the a9 to an entirely contrast-based setup in the a7S II. This is one of the most difficult features to test but I will try, and I will throw in some thoughts based on hours of experience with the a7 series. For the testing, I attached each camera to my slider so that I would have some consistency when it came to movement and positioning of the cameras as I switched them out. Then I used the Sonnar T* FE 55mm f/1.8 ZA wide open at f/1.8 and set up my ColorChecker Passport Photo as a target. Each of the cameras was set to AF-C with Wide area and then moved toward and then away from the ColorChecker.

Taken with the a7

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Taken with the a7R II

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Taken with the a7S II

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Taken with the a9

Luckily, nothing unusual happened during this round of testing. Each camera fell exactly where I expected it to. The a9 is remarkable, with its brand-new 693-point AF system, which you should read more about here. Combine this with its 20 fps shooting speed and you really have an insane camera for sports and action. Following this is the a7R II, which performed very well in this test, but in my time with it and in my original review of it, I found that it can have some difficulties keeping up with fast-moving subjects, something that the a9 does without any issue. Rounding out the phase-detect systems is the a7 II, which is still very good in decent light. The lack of coverage and additional points limit its capabilities for certain needs and applications, but is still very good for this class of camera.

Finally, we have the contrast-based a7S II, which does an okay job but is nowhere near the level of the other cameras. The a7S II is a video-centric camera where manual focus is usually prioritized so the lack of a serious AF system can almost be forgiven. However, in a head-to-head competition like this, the lack of speed here shows. It does perform well in single AF for photos though, so don’t entirely count this camera out for stills if you like everything else about it. Additionally, it should be noted that the a7 cameras are limited to just 5 fps.

Body Design

While all the cameras look extraordinarily similar, there are a few physical differences between them. I think the easiest way to do this will be to start with the a7 II and then explain what was added or changed with the next release. Though, to begin, we should say how the a7 II stepped up compared to the original a7 series.

Primarily, the key upgrade in the a7 II was the introduction of 5-axis SteadyShot INSIDE image stabilization, something Sony claims is a first for full-frame cameras. This camera was also the first to receive the redesigned body, with its more ergonomic grip and the repositioned shutter release. The a7 II also codified some of the changes that were introduced by the original a7R and a7S, such as the magnesium body and an all-metal lens mount. Beyond this, the camera’s screen received a resolution bump, and Sony made a claim of improved weather sealing.

The a7R II and a7S II have effectively the same body design, so we will group them for this section. For the most part, these cameras remained largely the same as the a7 II, so there isn’t as much to talk about, but there was a decent boost given to the EVF, which now has advanced optics and coatings, along with a magnification of 0.78x, up from 0.71x. The mode dial now features a locking mechanism to prevent accidental changes, and additional customization options were provided for the buttons.

Moving on, we have the a9, which is the most significant upgrade when it comes to body design. It has a larger, thicker, and more substantial build that makes it clear that the a9 is the flagship model. It adds another dial to the body for drive mode and focusing modes, repositions some buttons for easier access, adds a second SD card slot (and makes the primary slot UHS-II compatible), and offers a new joystick on the rear, alongside a touchscreen LCD. The lens mount has been further strengthened for working with larger and longer lenses, and Sony introduced a new battery pack with more than double the capacity of the a7 series. The camera even offers better sealing for working in less than ideal conditions.

There is a quite clear progression of build quality that matches up with the release dates of the camera models. While you likely won’t choose from these cameras based solely on the design of the body, is it nice to know what you get or don’t get to further guide your decision.

Video

Like it or not, many people are buying mirrorless and DSLR cameras to shoot video with them. So, here is a comparison of all four cameras and how well they can capture video. To keep things easier to compare and understand, we made sure to test each camera with its “best” modes and to output everything to an external recorder so that the footage is all on an even playing field. These modes would be the a7 II in full-frame Full HD, the a7R II in Super35 UHD 4K, the a7S II in full-frame UHD 4K, and the a9 in full-frame UHD 4K. If you are looking for more thorough comparisons between various modes and, particularly, the gamma options, you may be able to find some answers in an earlier article where we compared the a7R II, a7S II, and FS7.

Detail

Every one of these cameras has a different sensor and video-capture options, so detail is going to be an interesting element to examine. This is also where we will look at other image issues such as aliasing and moiré. For video, many of the issues show up when motion and fine detail is present in the footage, so I went outside and captured a nice wide shot that includes some trees and patterns. Below you can see how everything turned out.

This resulted in a very interesting test, since every camera has its own method of processing the data. Unsurprisingly, the a7 II, having only Full HD as an option, has the lowest amount of detail but, surprisingly, the a7R II and a9 surpass the a7S II when it comes to detail. The a7S II offers many advantages when it comes to video, but the 1:1 pixel sampling can’t resolve as much as the downsampling techniques used in the a7R II and a9, though minimal sharpening in post can make the footage shine. Comparing the a9 and the a7R II, the a9 appears to have slightly more detail in the final image, with the leaves on the tree being a hair sharper.

Rolling Shutter

The bane of almost every DSLR/mirrorless camera’s video capabilities is most certainly rolling shutter. This jelly-like effect is unavoidable for the most part and can be very unsightly. To keep everything the same and make it easy to see what was happening, I set up a motorized slider with some targets in front of it, allowing me to keep the same speed with each camera as I switched them out.

You can see that this one is pretty straightforward by looking at the images. The a9 has the best controlled rolling shutter, followed by the a7S II, and then the a7R II. Though it isn’t shown, the full-frame 4K mode of the a7R II is significantly improved, but at other costs to overall image quality. I left the a7 II out of the initial list because it is limited to Full HD, but its performance is good for 1080 and is better than any of the other cameras’ 4K modes.Dynamic Range

There are various gamma options available on all these cameras including standard, S-Log2, S-Log3, Cine4—each with its own method of squeezing out the most dynamic range possible. For our tests, we stuck with S-Log2, since it’s available on all the a7 models, to have a more direct comparison. From personal experience, S-Log2 tends to work better with 8-bit footage from these cameras because S-Log3 was designed to work with cameras capable of holding a lot more color information and data. Nevertheless, S-Log3 is a nice option on the a7S II if you intend to use it as a B camera with a larger system and need to keep everything as close as possible for consistency in the edit. The a9, however, doesn’t have any Picture Profiles so I had to set up the Neutral style with all the settings turned down.

It is easy to see that the a9 is at a major disadvantage by not offering a log gamma profiles in the camera. Shadows are being crushed or highlights are being blown out, and there isn’t much you can do about it. Sony’s pitch here is that the a9 is not intended to be a video camera and is focused on speed and still-image capture, which is fair, but after looking at its performance in other aspects, I really wish that they did add it in here, because it could be really good. Unfortunately, it loses out here to the a7 series.

The winner, by a very small margin, is the a7S II, which was expected given its video-centric design. A lot of this is thanks to the impressive low-light performance, which allows users to pull clean details out of the shadows when they expose for the highlights. The a7R II is no slouch here either, and the a7 II is quite close, but since it tends to introduce noise sooner than the others, I would rate its usable dynamic range slightly beneath the others.

Low Light

Though this should be similar to the stills results, the way that some cameras process video can result in significant changes when you hit Record, compared to snapping a photo. All the cameras are impressive in this regard, though, as expected, the a7 II is somewhat beneath its more advanced compeers. The clear winner is obviously the a7S II, which is known for its abilities in video and low light, so this makes sense. By my eye, the a9 has much better control over noise, especially color noise, than the a7R II, though it may be through the implementation of a more advanced noise-reduction process. Also, the a9 goes up to ISO 204800, whereas the a7R II is limited to ISO 102400. Check out the video below to make your own determinations here, especially the points when the footage may become unusable for your purposes.

Conclusion and Recommendations

There are some obvious winners here but, in the cases where it can go either way, we hope there is enough information above for you to make an informed decision. There are a couple of things I want to point out, primarily, the fact that while all these cameras are comparable it is still a bit unfair to put them head-to-head like this. The a9 and a7 II are placed at completely different prices and were released years apart from one another, and then the a7R II and a7S II are both specialized tools that are destined to falter somewhere in the feature set. All the cameras performed extremely well, and you really shouldn’t have any issues to worry about. Use this information to know more about how your camera performs in certain situations, to help yourself create even better images.

Still uncertain about which one to get? Have your own thoughts on Sony’s full-frame mirrorless cameras? Have some questions that weren’t quite covered in this article? Feel free to let us know in the Comments section, below!