Why Mirrorless ?
What is a Mirrorless Interchangeable Lens Camera (MILC)
and
How does it differ from a Digital Single Lens Reflex Camera (DSLR) ?
Why am I writing this article ? I was talking about cameras with family members recently. The subject of discussion was a Nikon 1 V2 camera. The question was put …”What kind of camera is that” ? I said “It’s a mirrorless interchangeable lens camera, not a digital single lens reflex camera, OK” ? They replied…”What are you talking about, we don’t understand any of those words”.
These particular family members are pretty smart people but they are, like most other people, just not camera geeks.
(very) Brief Historical Background For many years if you wanted to step up to better picture quality from a compact camera, you got a Single Lens Reflex (SLR). In due course film gave way to digital and the SLR became a DSLR.
Leica can probably claim to have been the first to introduce a MILC with it’s original 35mm film M series rangefinders dating from 1954, and also the first to introduce a digital MILC with the M8 of 2006. But M Leicas occupy a select niche with manual operation and very high prices.
The MILC entered the electronic era with the 2008 release by Panasonic of the G1 which was the first camera made to the new Micro Four Thirds (M43) format. Olympus soon followed with it’s own M43 cameras. Other makers were not far behind with their own interpretations of the MILC theme, using a variety of different sensor sizes and proprietary lens mounts.
Now all the makers of interchangeable lens cameras offer some kind of MILC. Some, such as Panasonic, Olympus and Fuji are fully committed to mirrorless ILC’s. Others such as Canon, Nikon and Pentax remain heavily involved with DSLR production. Sony appears (although this is not entirely clear) to be in transition to an all mirrorless model lineup (maybe).
The DSLR Has it’s roots in mid 20th Century technology. It is essentially a mechanical/optical device onto which has been grafted autofocus and digital image capture. It’s effective operation is highly reliant on optical and mechanical components which must be manufactured and assembled with a high degree of precision. These include the flipping mirror, submirror, autofocus module, focus screen and pentaprism.
The MILC Is a creature of the 21st Century and of electronic technology. The MILC does away with the mechanical components referred to above. It replaces the optical viewfinder (OVF) with an electronic viewfinder (EVF).
What are the advantages of the MILC ?
Size/mass Much of the manufacturer’s promotional material for the MILC concept strongly emphasises the reduced body size made possible by the new technology. This is all true of course but maybe not as important to consumers as the makers appear to believe. There could be several reasons for this.
- Cameras can get smaller but the hands which hold them do not, so there reaches a point at which the camera body is so small it becomes difficult to hold and operate confidently.
- DSLR’s can also be made quite small.
- We are talking about cameras which use interchangeable lenses so we need to consider the size and weight of a camera body with several lenses. As it happens, lens size is mainly determined by sensor size which is unrelated to the question of DSLR vs MILC technology.
- EVF vs OVF The debate about the relative merits of the two types of viewfinder continues to find energy on camera user forums. However as EVF’s improve with each iteration and given that the OVF reached the end of its’ evolutionary journey many years ago, the balance is gradually shifting in favour of the EVF.
OVF advantages
- A good quality OVF provides better highlight/shadow detail than even the best current EVF’s, especially in bright sunny conditions, but the gap is closing.
- With continuous shooting an OVF preview image refreshes at the speed of light which we all know is pretty darn quick. The best EVF’s are not yet as fast. ?
EVF advantages
- Preview image brightness can be configured to remain constant in bright or low light. It can also be set to emulate the effect of exposure compensation.
- The EVF can be adjustable for brightness, contrast/saturation and color balance, to suit individual requirements.
- The EVF can be configured to a variety of image preview and review formats. The aspect ratio can be selected. The preview type such as SLR style or Monitor style, can be selected.
- A large number of user selectable image overlays can be displayed or not displayed, to user preference.
- The EVF typically displays a 100% accurate image preview size and boundary. Most OVF’s do not.
Segue from eye level view to monitor view
The DSLR is really two cameras inhabiting the same body shell. With eye level viewing the light path passes through the lens, is partly reflected off the flipping mirror, travels up through the focussing screen, pentaprism and viewfinder eyepiece. But switch to monitor view (often called live view in DSLR parlance) and the light path is completely different. The mirror flips up and the camera now functions like a MILC, with image preview, focussing, and exposure measurement all derived from the imaging sensor.
With the MILC there is no need to switch from one view to the other. They are the same view, streamed directly and continuously from the imaging sensor. The EVF and monitor can be configured to have exactly the same appearance and features. [note: not all MILC’s currently offer this facility. They should, it makes a big difference to the user experience.] Look at the monitor, you see the monitor. Look at the viewfinder, you see the EVF. The segue from one to the other is seamless.
Whenever I use a DSLR I am reminded of just how clunky and discontinuous is the DSLR experience when switching view modalities, compared to the smooth and seamless experience with a good MILC.
Auto Focus In a DSLR there are two completely different autofocus systems. (Sony SLT’s use one system).
With eyel level view AF is managed by a module in the base of the camera. This receives light passing through the semi reflective flipping mirror, onto a submirror, then to a series of prisms and lenses making up the AF module. This system has two characteristics
- It can be very fast
- It is prone to inaccuracy from two sources
* The slightest misalignment of the optical/mechanical components of the AF pathway will lead to repeatable AF error, i.e. always too close or always too distant.
* The Phase Detect AF technology used is subject to random type errors. This is because the PDAF system determines where it thinks a lens focussing module should be sent and does so. This is fast, but does not confirm exact focus hence the inaccuracies.
With monitor viewing the DSLR uses the imaging sensor for autofocus just like the MILC described below. However many DSLR’s focus very slowly in monitor view as their on sensor AF technology is not as advanced as that in MILC’s.
With a MILC autofocus is always determined right on the imaging sensor. It can utilise phase detect (PD), contrast detect (CD) or some combination of both.
The AF speed of early model MILC’s was slightly slower than typical DSLR’s. However as I quickly realised when I started comparing my early model Panasonic MILC’s to my mid range Canon DSLR’s, the Panasonic MILC’s were very much more consistent and accurate in all conditions. It was in fact this inconsistency with Canon DSLR AF which caused me to move to MILC’s.
AF speed in MILC’s has now increased to the extent that many are now both faster and remain more accurate than DSLR’s with single shot capture.
Continuous Autofocus (follow focus on moving subjects) While many MILC’s are now comprehensively better at single shot AF than DSLR’s the same is not true for follow focus capability.
One of the issues here is EVF blackout time in MILC’s. Because viewfinder blackout is longer (than a DSLR) after each frame, using the MILC for continuous AF at high frame rates is difficult. The other issue is that the makers of MILC’s are not yet quite up to DSLR speed with their on sensor AF-C systems. There are some exceptions to this, notably the Nikon 1 series V1 and V2 cameras which allow 5 or 15 frames per second with AF on each frame.
Mirror Slap vs Shutter Shock DSLR’s can produce unsharp photos at certain shutter speeds (often around the 1/8-1/4 sec range) due to vibrations caused by the flipping mirror. Some MILC’s can also exhibit unsharpness with some lenses in some conditions due to the initial closing action of the focal plane shutter. This has been reported in the shutter speed range 1/20-1/160 second and is often referred to as “Shutter Shock”.
Cost At the moment, DSLR makers are working to retain market share with aggressive discounting. And it must be said MILC makers are doing the same thing with runout and discontinued models. However when the silly season is over, assuming it will ever be over, and the makers of MILC’s have recouped more of their R&D costs, there are reasons for believing that MILC’s can be inherently cheaper to make than DSLR’s. They have fewer components to make and assemble, fewer components which require accurate location in three dimensions and more electronic components which should be cheaper to mass produce and easier to assemble.
Evolution The DSLR evolved from the film era SLR. In the 1980’s the SLR acquired autofocus and in the 21st Century it replaced film with digital capture. In the process it acquired a monitor screen on the back and lots of buttons to control the electronics. But the basic architecture remains. There is a discontinuity between eye level view and monitor view. The flipping mirror and other optical/mechanical components remain in place. Sony tried, with some success, to address these concerns with it’s SLT variant of the DSLR theme. But these cameras have a translucent mirror permanently located in the image forming light path and they do not permit reduction of the flange back distance. For these reasons I suspect the SLT variant is unlikely to have long term prospects.
In effect DSLR evolution has come to an end. The basic architecture is locked in. Most of the recent technology advances seen in DSLR’s, such as improved sensor and image processing technology, could be applied to MILC’s or any other kind of camera.
The MILC however can be any shape or size, almost without restraint. The EVF can be located just about anywhere. Technology will improve EVF and AF-C performance.
As many operations on a MILC are drive by wire, the function of user interface modules can be user assigned for a high degree of configurability.
What do MILC’s need to improve ?
I nominate three main areas in which improvement is needed.
1. Improved EVF appearance, smoothness in low light and refresh rate.
2. Improved follow focus capability.
3. Elimination of shutter shock by moving from mechanical to electronic shutters.
I believe each of these challenges is amenable to a technological solution. Many current model MILC’s already incorporate partial solutions to each.
You can read more discussion about mirrorless cameras on my Camera Ergonomics blog at http://cameraergonomics.blogspot.com.au
18 Responses
Thanks for your post!
In your (dpreview?) graph, it’s not really fair to show a SLR with a zoom lens compared to a MILK with a prime lens on it.
Sorry, I added the image. The author didn’t show a picture and I wanted to have something as header 🙂
I have often felt that these explanations overcomplicate things for most people. These articles are good for people getting serious about photography. If this is for the people you describe, it’s not going to get you anywhere.
The bottom line is they are ALL interchangeable lens cameras. That’s really all the vast majority of people understand. At this point in the game the only thing that people should understand is perhaps the pros and cons of the sensor size, and what brand/system may be better for certain types of photography. And, even then, you’re probably talking to someone who is more serious than the average person. I have tried to explain the differences to very intelligent people, and they just glaze over. With the exception of very fast moving subjects or very shallow depth of field, there’s really no reason for most to go with the traditional ILC’s anymore. Not to mention, that gap is closing very quickly. I’ll bet in a year or two, focus tracking will be all but a problem of the past. Also, trying to explain mirror slap, or contrast vs phase detect, or optical vs electronic to a newbie makes them apprehensive and they say, I’ll just get a Canon or Nikon. I’ve seen it dozens of times.
One big mistake that the mirrorless companies have made is not driving home the idea that these are “SLRs in smaller bodies.” For 99% of the average person’s needs, it is all they need. People (not enthusiasts or pros) really don’t care at ALL about sensors size, phase vs contrast detect, optical vs electronic, etc. They want something that gets the shot. That’s it. Improved focus and shutter lag over a point and shoot is the main reason people buy Canons and Nikons. If they understood that these smaller ILC’s can do that Canon and Nikon would be much more worried (especially Canon)
Berneck: not that it affects your main point, but you should not be mentioning sensor size (and extremely shallow depth of field) as an advantage of DSLRs over Mirrorless ILCs. For DSLRs, you have FF (5DmkIII, D800, etc), APS-C (D7100, 70D, etc) and 4/3 (E-1, though not really supported anymore.) Likewise, for Mirrorless, you have FF (A7/A7R w/ more coming), APS-C (NEX-7, Canon M, etc) and 4/3 (E-M1, GH3, etc), as well as some odd smaller sensors (Pentax Q and Nikon 1.) Smaller sensors are not an inherent difference. The only real differences left are that on-sensor Phase Detect (as well as Contrast Detect) is not as good for tracking YET as the separate Phase Detect in DSLRs (well, the higher-end ones, anyway) and the old EVF vs. OVF debate. The quality of the latest EVFs is so high that it’s really just personal preference now (i.e., one is not better, but they are different with their own strengths and weaknesses.)
Yeah, you’re right. Although, I wasn’t suggesting that a dSLR is the way to go to get extreme DOF. I was saying that sensor size in some cases may be more of a factor than focusing on dSLR vs mirrorless. My whole point is that there is so many articles out there explaining mirrorless vs dSLR, that it’s not really as important as other factors.
You make a very good point.
Most of those looking at interchangeable lens cameras look for one of the following features:
1. shorter lags (AF, shutter and shot-to-shot)
2. wider dynamic range (often referred to as “richer colors”)
3. better subject isolation (referred to as “sharper photos” or “blurred backgrounds”)
This population regards the interchangeable lens bit a liability. The limited FL range of affordable zooms and the lack of a built-in “macro” option are also considered as prices to pay. Size and weight are a smaller concern than, say, price and brand recognition while the internal mechanisms are of no significance whatsoever. I’m afraid trying to educate such casual shooters is mostly a waste of time.
I think that the appearance of advanced bridge cameras such as the RX10 and Stylus 1 has the potential to disrupt the sales of entry level ILCs, DSLRs and mirrorless alike.
sneye, great points. It can be summed up simply by saying, “Same great picture quality, much less weight.” The photos showing a A7r next to a D800s don’t hurt either.
Found your MILC article intetresting.
One issue was not discussed regarding the costs of MILC’s.
You wrote: “Cost At the moment, DSLR makers are working to retain market share with aggressive discounting. And it must be said MILC makers are doing the same thing with runout and discontinued models. However when the silly season is over, assuming it will ever be over, and the makers of MILC’s have recouped more of their R&D costs, there are reasons for believing that MILC’s can be inherently cheaper to make than DSLR’s. They have fewer components to make and assemble, fewer components which require accurate location in three dimensions and more electronic components which should be cheaper to mass produce and easier to assemble.”
Another element regarding Costs is there are a few Camera Manufacturers that are fearful that MILC’s will ‘canabalize’ sales of their DSLR’s.
For this reason Nikon introduced the ‘1’ System cameras, which today are considered market place failures. The reason in my opinion is Nikon introduced this system to avoid losing DSLR sales.
If the ‘1’ System was designed to serve photographer’s needs it would be a success today.
My point in all of this is to alert those thinking about an MILC to make decisions based on the what the camera can do and not on a camera company’s marketing hype.
I have never used a Nikon 1 camera, but from what I have read, they are very fast and accurate, and track focus well. In my opinion, that’s all that most people need. The problem is, nobody knows the capabilities of these cameras. They regard them as expensive point and shoots.
If the Nikon 1 cameras had CLS flash capabilities I would own them right now regardless about my feelings on the lower IQ 1″ provides.
Nikon ‘Dumbed Down’ the 1 system cameras to protect their DSLR market place.
Nice overview.
There is one more area where MILCs are behind, way behind. That’s battery life. EVIL battery capacities will need to at least double to come anywhere near par between the systems. I can easily get over 1000 frames on one charge with my D600. My NEX 6 gets about a third of that. Even carrying two extra batteries I’ve run out of juice in a day with the Sony. Carrying four extra seems extreme, but that’s what I need to make sure of I don’t run out. That’s still fewer exposures than I get with one extra Nikon battery. The requirement for extra batteries also cuts down somewhat on the MILC weight (not to mention battery management)- and potential cost – advantage.
Battery life is a long-standing problem. NEX-6/7 are somewhat forgivable: they are relatively small. But I was surprised and baffled to see that the largish E-M1 and GH3 do not use larger batteries. At best, they only provide extra juice the portrait grips.
Agreed, they are “behind” only because the sensor is constantly activated, and of course the EVF and rear screen are constantly on. However, considering this obvious increase in energy use, battery life really isn’t so bad. I rarely have issue with it, and just make sure I have a spare battery.
That being said, I kind of laugh when someone complains about getting 300 pics vs 1000. If you are taking 1000 pics in one day, you are most likely trying to get lucky instead of truly enjoying a moment, and capturing good photographs. I used to come home home from vacations with thousands of pictures. Over time I realized a) I spent more time behind the camera than truly enjoying the moments, b) my photography wasn’t improving at all. I was simply taking every crazy angle hoping to get that one good shot, instead of really trying to get one good shot.(there is a difference). And c) there is no way in hell I could ever look back through thousands of pictures and actually enjoy them.
Unless you are doing some sort of stock photography, the battery concerns are overblown. And even then, if you’re a pro, you have plenty of backup and know when to change out batteries, etc.
I would also add, the beauty of digital over film is that it costs nothing to take thousands of pictures. However, I argue to get really good at what you do, you need to actually take less pictures (meaning pressing the shutter button less, not less time getting out), and focus on making every shot count. I actually sometimes pretend I have a few rolls of film, and will not shoot more than say 70 or 100 shots in a day. I have gotten much better as a result, because it really makes me think about how I’m shooting.
For pro work, it is not uncommon to need to shoot many frames, and in my opinion, battery life is a major impediment for mirrorless for pro work at the moment, more so than continuous focusing.
It’s also not just the number of exposures. With DSLRs, I can be in a shoot for hours with the camera on, even if I don’t fire off thousands of frames, and still have enough juice to get me home. Many mirrorless cameras quote battery life of around 300, but more often than not, that number is not really reached with constant EVF / LCD use over a period of time, even if the shot count is low.
Battery charging routines and power management are also made complicated when traveling. I used to carry 2 batteries and a single charger with a DSLR for travel assignments, and found that with mirrorless (this was in the X100 days) I carried up to 7 batteries with 3 chargers to ensure as many of them are charged as possible, because on assignment, often times when I head out in the morning I do not come back to the hotel until late night, and before sleeping charging as many batteries as possible is an absolute must.
The Leica M240 fixed that problem (sort of) with a large battery for over 600 shots – this is something we need mirrorless camera manufacturers to wake up to – putting large capacity batteries into those mirrorless cameras….. especially with all the Wifi / GPS features they like to cram into these new devices…..
Battery life is a non- issue for me because I always carry enough extra batteries to get me through a shoot. They are small enough to fit in any of my various bags.
Also when shooting in the cold it is always usefull to have extra batteries in your pockets close to your body for warmth.
A cold long lasting battery is just as dead as an ’empty’ short lasting battery.
I agree with Michael, the batterie life is one of the biggest issue with mirrorless (or compact) camera. When I do multiday hiking, camping or traveling into country where I know it will difficult to charge batteries, I bring my DSLR. The battery concerns are really not overblown.
EVF v. OVF. After few month with the GX7, honestly, I’m still missing the OVF. But that is the nostalgic “missing”. To me, the EVF easily outdoes the OVF on the general utility making overall shooting experience much much smoother. (OVF is a glass window – EVF is a heads-up display.) Real-time exposure compensation (and BW) preview, zoom, focus peaking, level – all readily available in EVF – those are the things I doubt I can give up now. Refresh rate is more than sufficient and lag is negligible.
What I was the most pessimistic about is the digital blackout. But to me personally in practice that turned out to be not an issue: GX7 is snappy enough and I’m not very interested in the burst shooting.
If I could pick 3 areas to improve on my GX1 it would be:
1) Add wifi and/or bluetooth interoperability so I can share photos to the cloud or Facebook.
2) Be able to do quick edits like on my iPhone to either improve exposure, add vignetting, or add little Instagram-like filters.
3) Better on board flash. The iPhone 5S is a revolutionary flash but nobody is giving it much press. It includes two color tones (cool and warm) as opposed to traditional on board flashes which just has one. Apple solved the problem with the flash to make a more natural looking shot to which the traditional Japanese camera makers should be beating their heads in saying, “Why didn’t we think of that??”
Don’t understand the comments about pros using MILC cameras. If I were a pro there’s no way I’m slinging an MILC. The first thing I’m grabbing is a 5D Mark III. No way any mirrorless is going to compete with a full frame, it’s a simple matter of physics. MILC are cute and nice for the average consumer, not for professional work.
Technology for cameras is changing so fast who knows what we’ll be using 3 years from now. MILC’s have only been around since 2008, that’s not that long ago. Sony’s new lenses designed to slide over a smart phone or tablet may be the wave of the future for all I know.
As far as I’m concerned photography today (for the average consumer) is all about the cloud. It’s about touch screens, instant sharing, social networking, and portability. Cameras on smart phones are advancing at a far greater rate than either DSLR’s or MILC’s.
For crying out loud, Nokia already has a 41mp camera on their Windows Smart phone. It’s entirely possible 3 years from now we’ll all be using smart phones to take our pictures if Apple or Nokia can pull off some technological wizardry.
If Apple were to come out with a dedicated camera with full cloud connectivity I’m convinced they could completely alter the photography landscape and dominate. They’ve already demolished the low end Point and Shoot category and I don’t think they will stop there. I think the Japanese camera makers are all entrenched and stuck in their old ways and I don’t think they see the tidal wave that’s coming.
Apple has the potential ecosystem to tie your camera in with all their other devices, Apple TV, iPhone, iPad, Mac, iCloud, Siri in cars, etc. wirelessly, simply, and easily. The only problem is, their camera is the one attached to the iPhone which isn’t very good in low light and doesn’t come with interchangeable lenses. It would be so nice to be able to say, “Siri, take the picture” and then it takes the picture. So many possibilities for the future of photography.