So now that Mirrorless is here, what is the features and functionality that makes this technology talk of the town? Why does it revolutionize photography and obsolete DSLR’s, and very importantly, are there no drawbacks?

Since features generally are used to segment the camera models and the market, this discussion is about what Mirrorless currently can do and what it will soon enable – across all brands and models pending on what the makers decide for each of their cameras. Also, it’s not at review of the current quality of a given feature. Since Mirrorless enables new functionality, If the feature has not already been perfected to DSLR level maturity, it will be very soon.

Please note this article is about photos - not movie mode - so I will not address what mirrorless brings when it comes to recording video. The movie mode advances are far bigger and more revolutionary than the changes to photo mode, so if movies are your thing, mirrorless is a no brainer.

But first, let’s get the drawbacks of Mirrorless out of the way. By drawbacks I mean things we are used to and expect based on using professional tier DSLR cameras. In reality there is only one real drawback plus a pretty annoying maintenance issue:

• No optical viewfinder (OVF). For many people the loss of the optical viewfinder will be difficult or perhaps even impossible. A VERY good screen/electronic viewfinder display will still be a representation of what the camera is seeing, with refresh delay, possible color mismatch, lighting “interpretation” and so on. No matter how many gains and advanced features that display will bring, it’s still not an optical real time view of the world.
• Mirrorless cameras is by definition a lot more prone to sensor dust specks. This is because when sensors are powered up they electrostatically attract more dust. In mirrorless it’s powered on during all activity (composing and so on), and for most models it’s never hidden behind a shutter. 

"For many people the loss of the optical viewfinder will be difficult or perhaps even impossible"

This is where die hard DSLR fans shout: AF and AF tracking is not on DLSR level, battery life is abysmal compared to DSLRs, and and and… So let my just reiterate: That is just semantics. Mirrorless uses Phase arrays and Li-Ion batteries just like DSLRs, so if it’s not a 100% on par yet, it will be in another Mirrorless camera model 😊 

So, let’s get to the advantages Mirrorless has brought so far – and a fair warning here, it’s a pretty long list:

• No Mirror, no prism and no dedicated Phase Array optical light path equals a nice potential for physical size reductions and weight saving for the camera house. But very importantly this does NOT extend to the lenses. They need to capture the same amount of light and details and thus need other technological advanced to get size reductions.
  Right now some would probably trade a little of the focus on massive size reductions in favor of better ergonomics and better battery. Camera models that address this will surely surface.
• With no Mirror to move in the camera...:
  - There are fewer moving parts which will increase reliability, potentially increase unserviced camera lifetime and certainly reduce production costs.
  - There is no longer the common problem of unsharp/shaken images because of the mirror slap and the vibrations it brings.
  - Frame rates can be increased above the physical limits a moving mirror imposes. Right now, 20fps is available but likely this will keep climbing and only be limited by exposure speed. A 100fps and more is certainly possible and already present in smaller sensors with less mega pixels to move. This is mostly limited by current data processing speed and shutter implementation.
  - Viewfinder blackout time at each shot will be reduced to the VERY brief shutter action time (which will also go away – more on this later)
  - The Mirror slap and this entire source of noise is removed.
• In DSLR the phase arrays used for focusing…:
  - Only sees the frame when the Mirror is down which is a problem during high frame rate shooting. In Mirrorless your Phase Arrays are located on the image sensor itself and are exposed to the frame almost continuously – also during high frame rate shooting. This increases the potential for much more reliable AF during shooting.
  - Sees a reduction in the overall incoming light to use for focusing because some part of the light is reflected by the main mirror to the viewfinder. In Mirrorless the on-sensor Phase Arrays gets all the light and can therefore become more sensitive in low light conditions.
  - Needs to be physically big because of the low light. Their numbers are also severely limited by the size of the camera house. At best there are a couple of hundred sensors covering ~50% of a Full frame. In Mirrorless they can be much smaller and spread out all across the sensor. Thousands of phase arrays and 99% frame coverage is already possible.
  - Are physically located away from the sensor and requires ultra-precise calibration and mirror action to focus at precisely the focal plane of the sensor when the mirror is up. This usually results in minor front or back focus issues at very large apertures (F1.8 or more). In mirrorless the phase arrays are on the same physical focus plane as the sensor. So, no micro adjustments like with DSLR are needed.
• With the Electronic Viewfinder a lot of new options become available:
  - What You See Is What You Get (WYSIWYG) is the obvious one – any settings you dial into your camera can be “realtime” computed and displayed so you see your end-result live.
  - Brightness is no longer determined by available light. If your eyes are bad in low light, dial up the brightness (will obviously affect WYSIWYG)
  - You can use realtime focus peaking which is a feature where the most in-focus parts of the frame are highlighted to show your current focus plane. This is a simple contrast analysis done by the processor - much like the old contrast detect auto focus in smaller mirrorless cameras.
  - Viewfinder size is only a design decision, it’s not limited by available light. It can be a small OVF like screen, the main camera screen or even a full-sized monitor if preferred.
  - Any kind of additional information that could make sense can be displayed in the viewfinder
• With the sensor always on and recording, any image dependent or computational additions the camera maker wishes to add is only limited by processing power. For now, this adds things like real face detection, real eye detection, much deeper and cleverer object tracking and of course automatic eye focus. The sky is the limit on this one.
• While it’s technically not a feature of Mirrorless, In Body Image Stabilization (IBIS) have only been deployed with Mirrorless cameras. IBIS is the art of moving the sensor physically inside the camera to counteract the vibrations and shaking that the camera is experiencing during exposure.

"A global shutter capable sensor promises massive improvements that mostly only affects Mirrorless cameras"

Some of the above advantages have not shown their full potential yet, and a few requires the usual advancements in processing power and refinement of technology for a couple of years to become fully mature. But it’s obvious that the potential is much greater than with DSLR.

The amazing part is we are not even done yet, because a new advancement in sensor design called “Global Shutter” is getting close to market. Simply said it allows the Sensor itself to stop recording light in all pixels at once – something that used to require a mechanical shutter on larger sensor cameras. You can read more about what a Global shutter is, and what it means in this dedicated article: The Shutter conundrum.

A global shutter capable sensor promises massive improvements that mostly only affects Mirrorless cameras. The DSLRs mirror design prevents it from enjoying most of the gains from this new technology.

With a global shutter, Mirrorless would gain these additional features over DSLR:

• Completely remove all moving parts in the camera, which will further improve reliability and longevity of the camera house without the need of service.
• The camera will become completely silent – no mirror slap or shutter chock.
• AF can now run 100% continuously during shooting as there is no shutter in the way
• Viewfinder blackout can be completely removed during all shooting
• With no mechanical parts an even higher frame rate is possible pending processing power.

"DSLR is singing its swan song"

I hope this little article opened your eyes to where camera gear is heading and why Mirrorless is so hot these days. Let’s not kid ourselves, DSLR sales will diminish greatly as the technology and R&D in Mirrorless perfects all of the above features. It has already stolen the R&D in DSLR from manufactures, so we will likely only see new DSLR cameras that was already scheduled and in development. These kinds of gains will definitely persuade the PRO’s once product maturity has been reached, and once the PROs go, high end amateurs go. Sales will start dropping significantly and then all development in DSLR will stop because the marked is not there.

The low-end marked is a given to mirrorless once manufacturers have the production facilities, knowledge and R&D down solid. They are cheaper to manufacture and offer more features. Just what the manufacturers and customers new to “serious” photography are looking for.  

DSLR is singing its swan song.