DSLR vs Mirrorless CSC

DSLR cameras (Digital Single Lens Reflex) have been the main tool of the professional and enthusiast photographer in the digital age, and before that the recent film era too (SLR). Over the last few years, a new style of camera the Mirrorless CSC (Compact System Camera) has made in-roads into the traditional DSLR market. Headlines such as ‘The Death of the DSLR’ have been seen in the photographic press for some years now. Many proclaim the Mirrorless is superior and the one you should buy. So we have some questions to answer.

  • What is the difference?
  • Which is better?
  • Which type is winning the market share battle?

What is the difference between a DSLR and a Mirrorless CSC?

The simple answer, of course, is the mirror. A DSLR has a mirror and Mirrorless don’t. So what is the mirror used for? It allows the light coming through the lens to be diverted into different areas inside the camera. This allows some of the light up into the optical viewfinder so that the user can see the image in the viewfinder in ‘real-time'. Some of the light is directed by a secondary mirror to a sensor array that is used by the auto-focus system. Finally, the some of the light is seen by the exposure metering system of the camera. So a very important part of a cameras functionality, you would think. At the moment of exposure, the mirror is raised to allow the light from the lens all to go through to the image sensor to capture the moment in time. Hence the ‘reflex’ bit of DSLR.

If the mirror has so much to do then, how can the Mirrorless camera do without the mirror? Firstly, all the light through the lens strikes the image sensor allowing the image to be processed continuously. DSLRs also have a mode called ‘Liveview’ that acts in the same way. The image is then made available to the electronic LCD display on the back of the camera, A second electronic display may also be added to make up the viewfinder.

Autofocus on the Mirrorless has to be accomplished by the camera analyzing the image contrast or by specific phase detection points on the image sensor. Canon also has a proprietary system called Duel-Pixel that can use 80% of the sensor to quickly determine focus, a system that has become their standard for Video auto-focus.

Exposure metering in Mirrorless cameras is done by analysis of the main sensor image.

Not having a mirror does allow the camera to be smaller and thinner with the lenses closer to the sensor than a DSLR. However, that means the Mirrorless will require a new set of unique lenses or you can buy an adaptor for some cameras that will allow you to use DSLR lenses. The latter rather spoils the Mirrorless cameras unique proposition as a smaller camera.

Is a Mirrorless camera better than a DSLR?

The Mirrorless camera is all about advances in electronic technology. The viewfinder, for instance, has come on leaps and bounds and the best cameras now have OLED viewfinder with 2.3M dots. When given a refresh rate of 100Hz then can perform very well in comparison to the DSLRs optical viewfinder. They can also display a previous image or overlaid graphics and text, unlike the optical version.

The main criticisms of the Electronic Viewfinder (EVF) are they can be very high contrast, flicker under artificial lights, be subject to blurring and take a lot of battery power. On the other hand, the DSLRs optical viewfinder cannot display previous images, text and show the image as it will appear in the final result. It comes down to personal preference and the type of photography you are doing. No clear winner yet.

Auto-focus has improved in the Mirrorless camera, but the DSLR has also made significant improvements. This is a real battleground but as technology improves so does auto-focus. The real difference is how much you have to pay for the camera versus its auto-focus capability. The lead is still with the DSLR at the high end but also the cheaper DSLRs. The best auto-focusing Mirrorless cameras are all mid-to-high priced.

Another major consideration is the size and weight of the camera. Olympus and Panasonic offer cameras with the smaller Micro 4/3 sensor size. This has an advantage in allowing smaller cameras but the sensors lack a little in quality, resolution, and ISO capability of the larger sensor cameras. Whilst they are often smaller in physical size they aren’t necessarily lighter. They are oft made of heavier metal parts where lower cost DSLRs are made from light-weight polycarbonate plastic.

They differ too in size, even with the same size sensor. For example, the Fujifilm X-T2, a very popular Mirrorless Camera, is much larger than the Canon M5, yet they both have the same size APS-C sensor.

One consideration about the difference between these camera types is the ‘style’ aspects. There is no doubt that the most stylish, retro-looking and desirable cameras are in the Mirrorless camp. The reason most DSLRs aren’t stylish is because they have been developed with function and handling in mind and they certainly do win on ergonomics.

The final and possibly more important aspect is the range of lenses available to a camera. DSLRs have been around longer and have developed a wider range of lenses. If you already have invested in lenses it makes sense to have a camera that can use them. You could choose a mirrorless that has an adapter available to convert the lenses for use. The only problem is you end up with a camera that is nearly just as big as the DSLR.

Currently, the APS-C sized Mirrorless camera of choice is the Fujifilm X-T2. This ticks many of the boxes in any comparison, but perhaps it’s Fujifilm investment in a superb range of dedicated lenses that makes this choice easy.

In the Full-frame sized Mirrorless cameras, the only real option is the Sony A7 series. The downside is the Sony lenses have been split down the middle with two series the A and E. This has led to the fragmentation that causes confusion and many photographers are choosing to use Canon lenses on those cameras anyway, via the Metabones adapter.

The lesson for camera manufacturers has to be if you are going to make a ‘system’ camera then make sure the ‘system’ is clear, coherent and comprehensive. On that score, you can see why Fujifilm have stolen a lead.

Mirrorless CSC vs DSLR - Market Share

Looking at the market share we have to take into consideration the overall digital camera market. This market has been sinking rapidly for several years now. This fall in the overall market will see a further -3.4% fall for Interchangeable Lens Cameras (Both Mirrorless and DSLR) in 2017. That will mean camera Brands fighting for market share. Any company thinking of launching a new Mirrorless CSC had better get it right!

From the chart above, we can see that the story over the last 3 years for DSLRs has been one of falling sales. Although it would be wrong to think this is due to Mirrorless cameras. They have flatlined for 3 years. DSLR sales have stabilized due to favorable prices and higher demand. Mirrorless cameras are running for the high ground.

The chart above shows the average unit price for the cameras, in ¥en. We can see that Mirrorless cameras have migrated to the higher price bracket whilst some DSLRs have reduced in price to improve sales in the enthusiast market. If Mirrorless only target the top end of their range they will find a very limited market.

The professional market still prefer DSLRs as can be seen by the take-up of the latest Canon 1Dx MkII and 5D MkII. These cameras will top the market for at least the next 3 years. So Mirrorless have the marginal professional market and the top end of the enthusiast market to aim for. If they cannot make a Mirrorless camera to compete both on performance and price they will always run second place.


The mass market of the last decade in digital photography has changed with the advent of the smartphone and tablet. The need to buy a stand-alone camera is now reduced considerably. Those who do want to buy a discrete still camera can be classified into at least three groups, professionals, enthusiasts, and beginners. Professionals will pay what they need to. Enthusiasts will pay what they can afford, whilst beginners will pay the least they have to. This all leaves Mirrorless cameras in a bit of a niche, attracting the affluent enthusiast whilst DSLRs can target all price points from top to bottom.

In my experience money is getting tighter for most people, so most buyers will be at the low, value end of the market. Even professionals will find it tough to commit large amounts to new high priced kit.

Given the above, Mirrorless will at best continue to flatline, whilst DSLRs will continue to outsell Mirrorless until at least 2020. The unknown factors are how much camera companies are prepared to spend on R & D without significant returns and just how good smartphone cameras get.

Things are going to get interesting.