Why Sony’s Full Frame Pro Mirrorless Was a Fatal Mistake


There is a big craze for Sony full frame (FF) mirrorless cameras at the moment, and seeing people rush onto that bandwagon is like watching lemmings following each other over the cliff.

Many fanboys can be heard triumphantly declaring the victory of FF mirrorless over the DSLR, but like George W. Bush’s declaration of “mission accomplished” this triumphalism is grossly premature. I am allowed to say this because I am a Sony FF mirrorless owner after I too was suckered into following the mindless herd over the cliff. It was largely a mistake. How could I have been so foolish?

I understand this is a controversial claim, so let’s go through the reasons for this bold statement. And before you accuse me of being a Sony hater, I can assure you that the increasingly frustrated A mount crowd are applauding me. For there is a simple question hanging over the FF Sony FE mount system: what is the point of professional grade FF mirrorless?

Claim #1: Compactness

The first answer you will hear to this question is that FF mirrorless is more compact. For example Sony manager, Kimio Maki, stated in an interview:

AP: Can you summarise the benefit of choosing an Alpha 7-series camera over a DSLR in a single sentence?

KM: Size. It’s all about size – it’s smaller and lighter. That’s the main reason of choosing our products.

Let’s examine this statement. I direct readers to camerasize.com where this comparison comes from:


It shows the Sony a7RII, Canon 5Ds, and Sony a99 each with a native 24-70mm f/2.8 lens mounted. As you can see, the total lengths are the same. Sony have failed to overcome the laws of physics. If you take something from the camera body, you have to give it back to the lens, and by the same amount.

So you have a choice: either buy one big body and lots of small lenses—or one small body and lots of big lenses. The former is more compact and the latter more bulky—plus FE mount lenses are more expensive. The more lenses you carry in your bag (I carry lots on my shoots), the worse the size disadvantage becomes. With larger lenses, the lens-body balance on the Sony mirrorless goes pear shaped: it’s like a bazooka mounted on a matchbox.

In many cases, Sony FF mirrorless works out as being bigger than a comparable DSLR:


This shows the Sony a7RII with the new 85mm f/1.4 GM lens vs. the Sony a99 with the Sony-Zeiss 85mm f/1.4 lens. This time, FF mirrorless works out bigger than a DSLR. The same thing happens when you compare it with a Canon DSLR:


Here the a7RII with the 85mm f/1.4 lens is bigger than the Canon 5DsR with the 85mm f/1.2 lens, despite the latter being half a stop faster.

Next, when you compare the Leica SL FF mirrorless camera with a DSLR, the lack of size advantage becomes even more stark:


This shows (from left to right): the Leica SL with the 50mm f/1.4 Summicron, Sigma 50mm f/1.4 ART lens with 5DsR, Canon 50mm f/1.4 with 5DsR, and the a99 with 50mm f/1.4 lens.

The only time mirrorless works out decisively more compact is when shooting with pancake lenses:


Here, the a7RII and a99 are shown with a 20mm f/2.0 lens. This was possibly the original design intention of FF mirrorless, but it became so irrationally popular that Sony started to develop big professional lenses for the system.

To maintain the illusion of size advantage, Sony and Zeiss seem to be peddling the grand revelation of the obvious that slow lenses make for more compactness as though this were some spectacular technological innovation. It seems that f/1.8 is the default maximum diameter for nearly all FE mount primes, with only a couple of exceptions.

The absurdity is that the 85mm f/1.8 Zeiss Batis gives you the same shallow depth of field as the APS-C Fuji XF 56mm f/1.2. What is the point of shooting FF if you can’t get more subject isolation than you can from APS-C? The only reason to limit aperture to f/1.8 is to make the lens more compact. But look at this:


Shown are the Sony a7RII with the Zeiss 85mm f/1.8 Batis, the Nikon D810 with the 85mm f/1.8, and the Fuji X-Pro2 with the 56mm f/1.2 lens. The field of view is the same, but for compactness, the APS-C Fuji is streets ahead. At maximum aperture all of these set-ups give you the same depth of field (along with the focal length also multiply the maximum aperture by the crop factor of 1.5 to get the FF equivalent; e.g. 1.2 x 1.5=1.8).

If compactness really were your priority, you would choose the Fuji 56mm f/1.2, which also allows you to shoot faster in low light. The Sony makes up for the slowness of the lens with IBIS, but this won’t stop action in low light. It makes no sense to limit the aperture speed on FF lenses merely for the sake of making a system more compact, as it defeats the point of FF.

To get meaningful compactness, you still have to drop down to a smaller format. Mirrorless APS-C really is more compact than DSLR APS-C:


Here the Fuji X-Pro2 is shown with the 56mm f/1.2 lens and the Pentax K-3 with the 55mm f/1.4 lens. Despite the Fuji having a lens half a stop faster, the system is more compact overall. Herein lies the problem: the size advantage of mirrorless APS-C fails to scale up to FF once lens size is considered. The body may be smaller but you can’t shoot without a lens. That is why with a 50mm f/1.8 lens, there is no size benefit from FF mirrorless:


Here the a7RII is shown with the new 50mm f/1.8 and the 5DsR with the 50mm f/1.8 lens. If you carry multiple focal lengths around with you at once on shoots, then professional FF mirrorless has a marked size disadvantage. Want an overall compact professional camera system (not just a body)? — buy a DSLR!

Now that the realisation has slowly begun to dawn that FF mirrorless loses its size advantage once lens size is considered, there is talk from increasingly desperate fans now begging for a “24-70mm f/2.0 FE mount lens that is more compact [sic] than the f/4.0 version”. But the delirious public have deluded themselves into thinking that Sony and Zeiss can collaborate to magically rewrite the laws of physics.

So what is the point of professional FF mirrorless systems?

Claim #2: Weight

The next answer you will hear is that a FF mirrorless body is still lighter and the height or width might be a bit less. However, that’s partly because Sony put such a miniscule battery in their FF mirrorless bodies that you end up having to carry multiple batteries, which negate any size advantage. You could make DLSR batteries smaller too, and they would still have better battery life than a mirrorless. The fuller body size of DSLRs is more to improve ergonomics, and could be made smaller, more like SLRs used to be back in the 1970s, if there were demand for this.


Here we see the view from behind of the Canon 5Ds R, the Sony a7RII, and the Leica SL.

So once again we find ourselves back to the original question. Other than as an amateur enthusiast’s compact walkabout system for shooting with a single pancake lens: what is the point of professional FF mirrorless? It certainly isn’t because it is more compact carried as a package with multiple professional grade lenses.

Claim #3: In-Body Image Stabilization

The next answer you will hear is that FF mirrorless is better because of In-Body Image Stabilization (IBIS). That’s like saying that Sony mirrorless is better because of the steak knives that they throw in. IBIS is hardly any more a unique technical feature inherent to the design of mirrorless cameras than either Wi-Fi or steak knives.

Sony have had 2-axis IBIS (“Steady Shot”) in their A mount DSLRs since 2003 when Minolta added it to the Dimage A1, and this could have been upgraded to 5-axis. Pentax, too, have just incorporated 5-axis IBIS into their K-1 DSLR. So IBIS gives FF mirrorless no inherent technical edge over other camera designs, but people are suckered into buying mirrorless by the offer of steak knives.

But Houston, we have a problem. There is also a major flaw with the implementation of Sony E mount IBIS. The Sigma CEO has been quoted as expressing grave concern for the narrowness of the FE mount diameter:

…the diameter is very small and makes it difficult to design high quality FF lenses … it almost looks like E-mount was designed for APS-C more than FF.

(Little wonder Sigma and Tamron don’t want to spend money on R&D for FE mount lenses, leaving us stuck mostly with expensive options from Sony and Zeiss.)

We also know that a narrow mount diameter is a big no-no with IBIS.

TAKASHI UENO: First of all, our XF mount is not compatible with IBIS. You may be thinking that our mount size is similar to competitors’ and why Fujifilm cannot do it. The answer is simple: for the sake of image quality. IBIS has both advantages and disadvantages. IBIS moves the sensor in the mount to stabilize the image. To secure the amount of light at any position, the diameter of mount must cover the wider image circle considering the margin of sensor movement. The diameter of our mount was designed for the image circle without IBIS. It means the amount of light at the corners is reduced when the sensor is shifted. We could correct it digitally, but we don’t want to do it: we don’t want to compromise our image quality.

TOMASH: Why didn’t you design a mount in a size, which would allow implementing the IBIS?

TAKASHI UENO: To cover the larger image circle, not only mount size (and body size), but also lens size must be bigger.

If you want IBIS, you have to design the mount in advance with a wider diameter, so that it doesn’t compromise corner IQ as the sensor moves around. What you don’t do is take an APS-C mount (NEX mount), turn it into a FF mount, then forcibly retrofit IBIS onto a mount never designed to take it in the first place. That’s why people expressed a lot of surprise when Sony added IBIS long after the launch of the FE mount FF mirrorless series, since normally a mount has to be designed to take IBIS from the start.


Furthermore, Zeiss has admitted that the short flange distance of the FE mount makes it technically challenging to design ultra wide-angle lenses: “The short flange distance between the sensor and the rear element is an engineering challenge for ultra wide-angle lenses”.

At really short focal lengths, the light hits the corners at too steep an angle, which is exacerbated by IBIS when the sensor moves. It isn’t without reason that Sony have yet to come up with any high quality wide-angle zoom lenses for the FE mount. They don’t even have a 16-35mm f/2.8 zoom, one of the so-called zoom trinity of bread-and-butter professional lenses. We may never see the appearance of anything like the Canon 11-24mm f/4 rectilinear lens, nor would it be predicted to perform well if it did.

It is a euphemism to call the FE mount an “engineering challenge”. The more honest expression may well be “technically flawed”, or just plain handicapped. Even if this handicap is overcome, with it come extra R&D costs that will be passed onto the buyer. It also retards the pace of lens development, explaining the slow rollout of FE mount lenses.

It is interesting to compare the relative diameters of various mounts:

Minolta/Sony A: 49.7mm
Sony E: 46.1mm
Fuji X: 44mm
Canon EF: 54mm
Pentax K: 44mm
Nikon F: 44mm

From this you can that see you are better off with the IBIS in their wide diameter A mount because it is more of a dedicated FF mount, not an APS-C mount. Canon is in pole position to add IBIS to the EOS mount because it is so wide, and if sensor resolution goes up to 120MP they will probably need it to reduce the impact of handshake, else it will be a tripod only model. It seems both Sony and Pentax are adding IBIS to excessively narrow mounts as a marketing ploy, with flagrant disregard towards optical fundamentals. It represents the victory of advertising over optics.

In any case, neither throwing in IBIS nor steak knives fails to convince us that mirrorless is an inherently better camera design. With that we return to the question: what is the point of professional FF mirrorless?

Claim #4: Adapting Non-Native Lenses

The next answer you get is that the main advantage of Sony mirrorless is that you can use non-native lenses with adapters. Asked about adapting Canon lenses, Kimio Maki, said this:

DPREVIEW: Do you anticipate that someone who has a collection of long telephoto Canon lenses could potentially use them to shoot sports with the a7R II?

KM: I hope that our native lenses are better! But it will happen. I see people using Sony a7-series bodies and third-party lenses all the time … because they already own the lenses. It works, but our native lenses are much better…

Adapters are fiddly and grossly impractical to use. I have a lot of adapters for my a7II, and have accidentally taken the wrong one with me or have forgotten to pack one altogether. It’s also an extra pair of lens caps to lose. Saying you chose FF mirrorless because of the size advantage so you can shoot with an adapted Canon lens is like saying that you’re going on a holiday to Hawaii so you can enjoy skiing on powder snow.

Adapters add bulk, and they decisively kill whatever marginal advantage in compactness the body might once have had. The body-adapter-lens combination looks like some ungainly Dr Seuss contraption.

Worse still, my Sony A to E mount adapter reduces light transmission by about a 1/2 stop, and you lose far too much of the native autofocus functionality, which gets immeasurably worse with Canon lenses. It is always far better to use native lenses—hence why Sony actually make native E mount lenses!


As Maki rightly says “native lenses are much better”. It’s a grand statement of the obvious that no fanboy wants to hear. Nobody raves on and on about the fact that you can adapt many vintage MF lenses to Canon and Nikon bodies then add focus peaking with Magic Lantern. Sony A mount DSLR cameras got focus peaking well before FF mirrorless even existed.

Micro-misalignment between lens-adapter-body also causes degradation of IQ in the corners particularly at shorter focal lengths (where due to the short flange distances and narrow mount diameter the E mount is “technically challenged” already because it was originally an APS-C mount). Being able to adapt vintage MF lenses might be cute, and certainly has its niche, but for all but a minority of legacy lens enthusiasts, the last reason for a professional to choose mirrorless is as a retro lens revivalist contraption.

At the end of the day, when I pick my set of lenses for a shoot, I just find myself systematically avoiding the use of adapted lenses. However much fun it is to play with vintage glass, I would gladly toss all of my adapters in the bin just to shoot with native lenses.

With that we have to ask again: what is the point of professional grade FF mirrorless cameras?

Claim #5: Live Exposure Preview


The next answer we get is that mirrorless is inherently superior because of live exposure preview. That means you get to preview the exposure in real-time through the EVF before taking the picture. This is something that is not yet the default modus operandi on most DSLR, but a new hybrid viewfinder patent from Canon suggests exposure preview is soon coming to DSLRs.

However, the Sony A mount cameras are an evolution of the SLR design, known as DSLTs (Digital Single Lens Translucent), which already have an excellent EVF for live exposure preview. Far from being slow like mirrorless designs, DLSTs can theoretically exceed the frame rate of a normal DSLR as the mirror doesn’t move, while retaining an autofocus just as fast.

So once again it just isn’t true to say that live exposure preview through an EVF is the one extraordinary feature that elevates mirrorless to the status of being an inherently superior design over other alternatives. Canon and Nikon DSLRs may not yet have hybrid EVFs, but if you were fickle enough to jump ship to another system every time someone else puts out a new model with some attractive new feature you would be doing it an awful lot.

So we find ourselves returning for the last time to the original question: what is the point of professional grade FF mirrorless? It isn’t for the compactness (beyond shooting with just one pancake type lens), certainly not for the faster autofocus, not for faster frame rates, not for EVF/exposure preview, not for access to a high cost-performance lens habitat, not for manual focus peaking, not for the ergonomics, and almost universally not for the sake of adapting lenses.

When it comes to FF professional grade mirrorless, the answer is that there is little or no point. People are buying into it because it is an irrational fad. You end up having to buy lots of big and expensive lenses for the one tiny body, when it is preferable to have lots of smaller lenses for the one big body, since the total lens-body combination is the same anyway due to physics. In actual fact the lens-body combination makes professional grade FF mirrorless multi-lens packages larger overall. The only time you get more compactness is when you shoot with just one short focal length pancake or quasi-pancake lens for use as a walkabout camera. The moment you carry around several professional lenses, all size advantage is lost.

Sony have created a niche for themselves through the marketing ploy of “product differentiation” by rushing down the path of FF mirrorless, where others like Nikon, Canon, and Fuji have feared to tread. Suddenly reviewers are raving about old features in a new bottle, as though they were spectacular unique features of mirrorless cameras—features like IBIS, focus peaking, and live exposure preview, things that were already present long before in the A mount DSLTs. But in actual fact there is a good reason why other makers have avoided FF mirrorless: because the all-crucial size advantage of mirrorless systems does not scale up to FF once lens size is taken into account.

The fad for a7 series FF mirrorless cameras is driven by irrational exuberance, and Sony are understandably capitalizing on crazy market demand-supply forces, even though they know themselves that it would have been more logical to have developed their A mount DSLTs, based as it is on superior optical design fundamentals. Sadly, perception is everything in the fickle marketplace, and rumour has it that Sony lost money on their a99 DSLT, which wasn’t the runaway success that their FF mirrorless series has become.

Sony's neglected SLT system has "superior optical design fundamentals."
Sony’s neglected SLT system has “superior optical design fundamentals.”

The Sony a7RII’s autofocus system, 5-axis IBIS, EVF, and the 42MP BSI sensor would have reached their full potential in an ultra-fast professional FF A mount DSLT system, and are being wasted on the slow-by-comparison FE mount mirrorless system. Whatever advantage Sony FF mirrorless seems to have now could have better been utilised in the next evolution of their SLR line of camera design.

The evolution of the SLR lineage of camera design is far from over. Between SLR and mirrorless designs, the battle has scarcely begun. Unlike the Sony/Betamax vs. Victor/VHS format wars of old, Sony has a stake in both camps. The current irrational bubble of frenzy over FF mirrorless is dangerously unsustainable, and evolutions of the more proven SLR designs may well turn out to be more resilient long-term.

Mirrorless FF Sony cameras are going through the usual cycle that goes with all novel technology. First some enthusiasts delirious with euphoria proclaim it to be the road to Elysian Fields, and boldly declare the triumph of mirrorless over DSLRs: “mission accomplished”. Next people find the Revolution to End All Revolutions brings its own set of problems, and it isn’t the golden path to Utopia it promised. Finally, people arrive at the more sober realisation that like rangefinders, it has its niche, along with its own peculiar set of pros and cons—mirrorless cameras being effectively digital rangefinders (which also lacking mirrors).

If at that point of stark sobriety you still think a mirrorless offers something for you then, that’s fine—as long as you don’t mindlessly jump on that bandwagon because it’s all the rage now to show off your FF mirrorless toy. I’ve been there done that.

If I were ever to buy another Sony body for my A mount lenses (like the amazing Zeiss 135mm f/1.8 and Minolta 300mm f/2.8) I would rather it be a new DSLT model, and will stick to Fuji for high-end compact mirrorless since when the lenses are as remarkable as Fuji’s there is negligible IQ difference over full frame.

Update on 4/5/16: Andrea P. of sonyalpharumors has published a rebuttal of this article.

About the author: Sator is a portrait and fashion photographer based in Sydney, Australia. You can find more of his work and connect with him on Instagram, 500px, and Google+. A version of this article was also published here.