Why You Should Stick with Your Canon DSLR and Forget Sony FF Mirrorless

Sator

EOS M6 Mark II
Oct 14, 2015
74
20
photonicshunkan.blogspot.com
A lot of Canon users are being tempted to shoot with a Sony FF mirrorless due to the ability to adapt Canon lenses, and lured by the thought that the grass might be greener on the Sony mirrorless side of the fence. It isn't. Before you accuse me of being a Sony hater, I should also say I have cross posted much of this on the Sony Alpha Forum and the A mount crowd are applauding.

There is a big fad for Sony FF mirrorless at the moment, and it is like watching lemmings following each other over the cliff. I am allowed to say this because I am a Sony FF mirrorless owner because I too was suckered into following the mindless herd over the cliff. It was a big mistake. How could I have been so foolish?

This is a controversial claim, so let's go through the reasons for this bold statement. The simple question hanging over the full frame Sony FE mount system is this: what is the point of professional grade full frame mirrorless?

The first answer you will hear to this question is that full frame mirrorless is more compact. For example Maki Kimio of Sony 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 allegation. I direct readers to camerasize.com where this comparison comes from:

http://camerasize.com/compact/#624.515,596.286,377.56,ha,t



It shows the Sony a7RII, Canon 5Ds, and Sony a99 with a native 24-70mm f/2.8 lens mounted. As you can see, the total lengths are the same. Sony has 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 economical and the latter is more expensive. The more lenses you carry on you, the worse the size disadvantage for mirrorless becomes.

In many cases, Sony FF mirrorless works out bigger:

http://camerasize.com/compact/#624.516,377.63,ha,t



This shows the a7RII with the new 85mm f/1.4 GM lens vs the a99 with the Sony-Zeiss 85mm f/1.4 lens. This time, FF mirrorless works out BIGGER than the rival DSLT model. 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.

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



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

Sony and Zeiss seem to be peddling the 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 FF 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 full frame 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. In terms of compactness, the APS-C Fuji is streets ahead. At maximum aperture all of these set-ups give you the same shallow depth of field.

If compactness really was your priority, you would be better off choosing the Fuji with the 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 help you 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.

Even with a 50mm f/1.8 lens, there is questionable size benefit from shooting with a 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, then professional full frame mirrorless has a marked size disadvantage. Want a more compact professional camera system?—buy a DSLR!

Now that the realisation has slowly begun to sink in that once the lens size in taken into account size advantage is largely lost, there is talk from increasingly desperate people 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 public have deluded themselves into thinking that Sony and Zeiss can collaborate to rewrite the laws of physics.

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

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

The next answer you will hear is that full frame mirrorless is better because of 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 wifi or steak knives. Pentax have just incorporated IBIS into their K-1 DSLR, and Sony could have put IBIS into their A mount DSLT system. So IBIS gives full frame mirrorless no inherent technical advantage over other systems, but people are suckered in by the offer of steak knives.

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

We 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.

http://fujilove.com/our-highest-priority-is-always-image-quality-interview-with-takashi-ueno-and-shusuke-kozaki-from-fujifilm-japan/

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 full frame mount, then forcibly retrofit IBIS onto a mount never designed to take it in the first place.

Furthermore, Zeiss has admitted that the short flange distance of FE mount makes it technically challenging to design wide angle lenses: “The short flange distance between the sensor and the rear element is an engineering challenge for ultra wide-angle lenses.” At short focal lengths, the light hits the corners at a steep angle, which is exacerbated by IBIS. It isn't without reason that Sony has yet to come up with any 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 anything like the Canon 11-24mm f/4 rectilinear lens for E mount, and it would hardly be predicted to perform well if it did appear. It is a euphemism to call the FE mount "technically challenged". The more honest expression may well be "technically flawed", or just plain retarded.

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

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


From this you can that see Sony were better off putting IBIS into their A mount, which has a wider diameter, because it is more of a dedicated full frame mount, not an APS-C mount. Canon is in a better position to add IBIS to the EOS mount because it is so wide, and if sensor resolution goes up to 120MP we will probably need it to reduce the impact of handshake. You can also see that both Sony and Pentax are adding IBIS to excessively narrow mounts purely as a marketing ploy, with flagrant disregard towards optical fundamentals. It represents the victory of advertising over engineering. For the credulous it represents Sony's triumph over the laws of physics.

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?

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 of Sony said this:

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 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. You can't have your cake and eat it too. Adapters are also fiddly, bulky, and they decisively kill whatever marginal advantage in compactness the body might allegedly once have had. Unfortunately, the body-adapter-lens combination ends up looking 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 fanboys wants to hear. Nobody raves on and on about the fact that you can adapt some vintage MF lenses to Canon bodies then add focus peaking to the body with Magic Latern. Micro-misalignment between lens-adapter-body 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 will have its niche, but for the vast majority of photographers, the last reason to choose mirrorless is as a vintage 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. I would gladly toss all of my adapters in the bin just to shoot with native lenses.

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 the default modus operandi on a DSLR, but a new hybrid viewfinder patent from Canon suggests exposure preview is soon coming to DSLRs. However, the Sony A mount cameras are DSLTs (Digital Single Lens Translucent), which already have an excellent EVF for live exposure preview. 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.

So we find ourselves returning to the original question: what is the point of full frame mirrorless? When it comes to full frame professional grade mirrorless, the answer is that there is 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 full frame 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 fad for a7 series full frame mirrorless cameras is driven by irrational exuberance, and Sony are merely responding to market demand-supply forces, even though they know themselves that they were better off developing their A mount system, based as it is on superior optical design fundamentals. Their autofocus system, IBIS, and the 42MP BSI sensor would have reached their full potential on the dedicated professional full frame A mount system, and are being wasted on the FE mount mirrorless system.

Mirrorless FF 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 declare the DSLR dead. Next people find the Revolution to End All Revolutions brings its own set of problems, and it isn't the magical path to El Dorado 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.
 

monkey44

EOS RP
Aug 7, 2014
430
0
Nice post --

I've shot with Canon for my entire professional life - WHY? Because Canon lenses and Canon cameras fit, react, and work for everything I need. In many cases the difference becomes minuscule between cameras and lenses when you compare brands. A little better in one area is offset in another.

And for the most part, unless you have the most technical eye in the world, you can't tell the difference between a photo created from an image shot with one camera or another, and most people cannot tell the difference, nor can anyone but a top tech (maybe?) even tell which camera shot it once it's printed...

Maybe some go to mirror-less for reasons other than quality of end product - but for me, I like continuity in my gear ... once I learned how to use it (going from film-slide to digital was a bit of a struggle at first) then any changes to my work-flow better be huge (Like the cost factor in digital vs. film) before I make any drastic change. Overcoming the expense alone becomes a burden -

Count me in for DSLR until something comes along that knocks me off my feet - maybe then, I'll switch, but the mirror-less factor alone ain't gonna do it ... nor will a competing brand simply because it can adapt to Canon lenses - Canon lenses work just fine with Canon cameras without all the hassle and worry of fit or breakage.
 

Mt Spokane Photography

I post too Much on Here!!
CR Pro
Mar 25, 2011
16,673
1,628
Thanks for posting, but --- do you actually expect anyone to read thru your badly overlong rant?

Please don't take this harshly, but it does get boring to have the same thing posted over and over.

Its been posted here 100's of times here about the fallacy of size and weight. I do not use a mirrorless because of three things.

1. EVF Viewfinders are not there yet.

2. Camera buttons and grip too small for my hands

3. Battery life is very short.

I like the idea of eliminating the mirror from a engineering standpoint, its just another thing to fail. However, I do not like EVF or small buttons.

If a small camera is wanted, a small sensor will allow for a smaller lens and smaller overall size and weight. The 1 inch sensor size is becoming the new compact camera standard, and is ideal for those who want or need small.
 

Aglet

EOS 5D Mark IV
Feb 26, 2012
1,728
15
AB
Uhmmm... So you're regretting buying an A7-something?.. ???

You could try some new G(?)-series glass on it for amazing IQ. Otherwise, it's a near DSLR-sized rig with poor battery life and very good raw files. I don't think the size of ML systems has ever been that big a draw vs SLRs and that's something easy to recognize going into it. If you're buying MILC, you're doing so for it's unique features and advantages and overall compromise; they don't smoke the competition in all facets of usability.

I LOVE my ML systems! Olympus & Fuji provide me with really great results and are quick and fun to use and save me post time because of the WYSIWYG EVF displays. And the EVFs are more than adequate for most uses on these systems and, to me, often preferable to optical VFs. Their overall system IQ is comparable to my best DSLRs. Oly's ergonomics and controls are great too, IMO; Fuji's not so much.

Trade-offs. If you have ML and DSLR systems you should readily be able to appreciate the advantages each one offers and use them appropriately and that's where the satisfaction comes in. :)
 

Khufu

...
Aug 2, 2013
334
0
35
Merseyside, UK
www.facebook.com
Wooooords... :-X

Focusing on the pictures though: it's the first time I've really had a look at the newer/mk2 A7 bodies and, looking at the wee theta marker thingy, I'm wondering why the frick Sony are putting the sensors so far away from the back of the camera bodies, leaving the mount poking out like that with dead space all around it... they've drawn up so many piles of blueprints and patents that I think they've lost track of the original post-it with "the point of it all" scrawled across the top.

That was fair amount if words too, wasn't it? Nevermiiind... ;)
 

Refurb7

EOS RP
Feb 13, 2016
255
49
Sator said:
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.

I think you've reached the right conclusions. I have reached many of the same conclusions, having bought, used and then sold a Sony A7 series. I am sticking with Canon and don't intend to buy another Sony (for a bunch of reasons).

However, I think your title may go a bit too far. If we accept your conclusion that FF mirrorless has its pros and cons (I fully agree), it doesn't follow that the general "you" should stick with Canon and "forget" Sony FF mirrorless. For some people, Sony's pros will genuinely outweigh Sony's cons (though not for me).
 

Khufu

...
Aug 2, 2013
334
0
35
Merseyside, UK
www.facebook.com
I love the idea of something like an RX1 (mk I or II, with OVF) ...but the price is ref**kulous. Throw together something with last season's FF sensor/processing tech in a worthwhile-small package with a decent consumer grade 24~50mm prime lens and I'll throw (less-than-RX1-RRP) cash at you!
 

pwp

EOS R6
Oct 25, 2010
2,530
24
Man that's the longest post I've seen this year. Read a bit then skimmed.
But got the picture clearly enough in the first 20%.

Negligible or zero size advantage and a big dose of buyers regret.
Plus having multiple systems sucks.

-pw
 

Sator

EOS M6 Mark II
Oct 14, 2015
74
20
photonicshunkan.blogspot.com
Refurb7 said:
Sator said:
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.

I think you've reached the right conclusions. I have reached many of the same conclusions, having bought, used and then sold a Sony A7 series. I am sticking with Canon and don't intend to buy another Sony (for a bunch of reasons).

However, I think your title may go a bit too far. If we accept your conclusion that FF mirrorless has its pros and cons (I fully agree), it doesn't follow that the general "you" should stick with Canon and "forget" Sony FF mirrorless. For some people, Sony's pros will genuinely outweigh Sony's cons (though not for me).

Thanks for your comments.

I've cross posted slight variants of this critique on different fora. This version is pitched at Canon (but could be Nikon) users, many of whom are being tempted to try a Sony FF mirrorless because it is the talk of the town. I really wanted to provide a bit of a counterweight to all of the positives that are frequently repeated, and to discourage Canon shooter from thinking they can easily use their Canon lenses on the Sony. Another point here is that all this talk of DSLRs being replaced by mirrorless is gross hyperbole of the sort that you get with rank novelties. I just want people to know that the whole lens-body package you get from Canon is still superb, so that people stop wanting to peek over the over side of the fence.

As a counterweight to my own critique I will say this. Sony should still be considered if:

1. You need 4K video
2. You need good low light performance
3. You love legacy lenses

There is a niche for the Sony mirrorless, which people should still consider after soberly weighing up pros and cons, but I am seeing too much irrational exuberance. I actually still shoot with my Canon tilt shift lenses on the Sony because of the focus peaking with manual lenses. I just wish Canon would add focus peaking to their bodies (yes, I know about Magic Lantern), since all of their TS lenses are MF.

As for the newer lenses coming out for FE mount, we'll see how they perform on independent testing. I am not terribly optimistic. People can go on about how Sony-Zeiss will perform magic and manage to overcome physics to make really competitive lenses for an APS-C mount being forced to double as a FF mount, but I am deeply sceptical. Tony & Chelsea Northrup suggested that the GM 24-70mm f/2.8 is only as good as the Canon, but costs $450 more. Sony still have no 16-35mm f/2.8 zoom in their lineup and that is considered one of the classic "essential" lenses. But I'm done and refuse to buy any more FE mount lenses altogether. I would be happy to buy more A mount lenses and bodies however, as I already have a few fine A mount lenses including a 300mm f/2.8.
 

No Mayo

EOS M50
Aug 3, 2012
43
0
Thanks, I appreciate your offering. I am a musician and a photographer and I have noticed that the best of both are the last to complain about information that they already know being presented, but instead find it interesting to see how the material that they know is presented by someone else. I have recently seen a few posts wondering what happened to some of our favorite members who used to post more often. I think that some of us may be more happy when we degrade another's offering. I appreciate and celebrate the best of this community and welcome differing opinions and a positive debate. I wonder if criticizing the length of someones post might reveal more about the critics reading level than it does about the author of the post. Peace to all and a special thanks to the givers of information that generously share with us all.
 

steyr

I'm New Here
Jun 24, 2014
9
0
Am I the only one who's sick of AFMA on DSLRs? To me the biggest advantage of mirrorless is being able to nail focus with a fast lens wide open.
 

d

EOS RP
Mar 8, 2015
417
0
steyr said:
Am I the only one who's sick of AFMA on DSLRs? To me the biggest advantage of mirrorless is being able to nail focus with a fast lens wide open.

No, I'm with you on that one. I've only played around with a couple of mirrorless bodies, but being able to get a spot on focus easily was something I liked about them.

d.
 

9VIII

EOS 5D Mark IV
Feb 8, 2013
1,843
0
Nice post.

Unfortunately all I read is that Fuji are awesome and as soon as they make that 33mm f1.0 that's being rumored then they're going to have a perfect system.
 

Hillsilly

EOS R
Oct 16, 2010
1,100
2
As a mirrorless user, accurate focus is something I appreciate. Also, interesting to note that the feature I like most, the EVF, is relegated to the bottom of the list of benefits.

As a Fuji user, I think they're smart in staying with the APS-C sized sensor. It should be noted that the photo in the initial port is their X-Pro2 - they're biggest camera. The more common, mainstream X-E2 and X-T10 models are noticeably smaller. And the 56mm is one of their bigger standard primes. Most of their lenses are smaller. Essentially, I'm trying to say that you can build a good Fuji kit that does have significant size and weight advantages over a DSLR kit, and it is one of the main reasons I shoot Fuji (and one of the reasons Sony has never really interested me - and you could add constant changes to mounts, RAW compression, build quality, service experiences, initial (and continuing) lack of lens choices that interested me, doubt about Sony's long term involvement etc etc).

Of course, one of the positive in Sony's favour is that their sensors are highly regarded. Their only real direct competitor in relation to sensor performance is Nikon. And Nikon have their problems, too. For some people, I can see Sony being a valid choice due to sensor performance alone.

But I agree with the general intent of the post. If you insist on using f/2.8 zooms, or longer, wider aperture primes, then what are you really gaining over a DSLR (assuming that there was a DSLR with similar sensor performance)? And I've never really considered IBIS to be that essential (or even preferable over lens based systems) but people using legacy lenses, primes without IS or making a lot of videos might disagree. And once Canon figures out how to incorporate an EVF into the DSLRs, then that advantage disappears, too.

Ultimately, people just need to do their homework.
 

Hillsilly

EOS R
Oct 16, 2010
1,100
2
9VIII said:
...Fuji are awesome and as soon as they make that 33mm f1.0 that's being rumored then they're going to have a perfect system.

mmmmm....33 1.0. I'm always surprised that nobody is interested in Fuji and that they are languishing at the bottom of all of the sales tables when they are making the sexiest gear.
 

Hector1970

EOS R
CR Pro
Mar 22, 2012
1,340
544
I enjoyed the post, it was a well made argument backed up by the use of visuals.
I've thought about Sony but all those issues pointed out were what would hold me back.
Certainly as a system with a series of pancake lens would be nice.

Canon rumors is great.
In two day it's put me off Sony and looking for more dynamic range in a camera.
Canon now seems just fine. Roll on the 5D IV
 

Sator

EOS M6 Mark II
Oct 14, 2015
74
20
photonicshunkan.blogspot.com
Hillsilly said:
As a Fuji user, I think they're smart in staying with the APS-C sized sensor.

Of course, one of the positive in Sony's favour is that their sensors are highly regarded.

I suspect that Sony's success with the a7 mirrorless series took them by surprise, and that it is a mixed blessing for them.

Firstly, they now have two competing full frame systems. The more popular of their two systems (FE mount FF mirrorless) was probably originally intended as a compact system for enthusiasts, but its popularity outgrew its original intent as a compact walkabout FF MILC system for enthusiast use. Now they have a funny FF MILC system neither fish nor fowl. The lenses are now too big to convince anyone that the system is compact. People are now demanding things from the system that Sony-Zeiss find hard to realise on an APS-C mount forced to function as a full frame mount. I bet that Sony sorely regret not increasing the mount diameter, and making the flange distance less shallow. Too late now! Unless they are really crazy and they launch a high-end mirrorless a9 series with a new, larger mount. They are much better off if they push the A mount as their premium high-end system.

Secondly, if Sony were genuine about making a high-quality compact system they should have just kept going with developing an APS-C MILC system. It would have been easier to implement IBIS on the E mount, and it would have kept the lens sizes from negating any size advantage. It would have complemented their FF A mount line much better.

They should have kept the 42MP FF sensor for the A mount DSLTs. They probably could have added IBIS to the A mount too since it is wide enough to accommodate it (it's wider than the K mount).

The trouble is that Sony were struggling with sales of their a99, which they apparently made a loss on (according to one rumour). They know that the A mount is their only serious pro level FF mount. They want to attack the market with A mount again (hence the rumours about the a99II), but they have trepidations. The trouble is that the market is fickle and irrational. The gush of sales on the a7 series is driven by irrational mania of a kind that really isn't sustainable. I don't blame Sony for capitalising on it while it lasts, but they are also profoundly aware of the limitations of the FE mount, so they better use the profits on the a7 to help propel R&D on the a99II.

Sony are dominant in the sensor market for now, but Canon will soon play catch up, and the Fuji-Panasonic consortium are working on an organic sensor. There will likely be more competition for Sony in future.