Selecting a Camera: Step 2 - DSLR or Mirrorless?

Right now one of the primary decisions someone is faced with when deciding to buy a camera, is whether to buy a Digital Single Lens Reflex Camera (or DSLR), or a Mirrorless Interchangeable Lens Camera (usually just referred to as a ‘mirrorless’ camera). This series of articles are geared towards someone buying their first camera, but equally many photographers who already have a DSLR are eyeing out the new breed of mirrorless cameras with interest. What follows below is our advice to someone trying to decide between the two.

(scroll to the bottom if you prefer tables to reading)

Read Part 1 - Selecting A Camera: Step One: Sensor Size

1 - Pentamirror 2- Focusing Screen 3- Mirror 4- Shutter 5- Sensor 6- lense array 7-Aperture

Some Background to DSLRs and Mirrorless cameras.

In essence all cameras do the same thing; light is transmitted through a lens and lands on a light sensitive sensor (or piece of film in the past). With DSLRs (and SLRs in the past) a camera has a mirror that reflects light into a pentaprism (or pentamirror for cheaper entry-level cameras) so that the photographer can literally look through the lens when composing an image. When the photographer presses the shutter on a DSLR a number of things happen: The mirror sitting between the lens and the sensor flips up out of the path of light, the aperture that controls the amount of light passing through the lens closes down slightly (if it was changed for the exposure), and the shutter curtains across the sensor rise and fall thereby completing the actual exposure. That’s quite a lot of things to happen in an exact sequence for the image to be made. This is why cameras are extraordinarily complex machines, and so expensive to boot.

Digital mirrorless cameras first appeared with the Panasonic Lumix DMC-G1 in 2008. This was fast followed by Olympus with their PEN EP-1 camera (which was also the first truly small mirrorless camera). Not to confuse the terminology, but what we refer to today as mirrorless is basically digital cameras that either don’t have a viewfinder, relying instead on the the rear LCD panel to compose images, or have an electronic viewfinder that uses the camera's sensor to ‘see through the lens’. In the pure sense of the word, mirrorless cameras have existed since the birth of photography as all cameras prior to the introduction of the eye-level SLR in 1943 didn’t have a mirror. Instead these cameras relied on everything from wire-frames to dual lenses to range-finder systems to give an accurate approximation of what the lens was ‘seeing’.

DSLRs are the continuation of the SLRs of the last century, while mirrorless cameras are modern equivalents where everything from focus to composition is driven off the sensor itself. Right now, if you walk into a camera store you have to decide on which system you are going to get the most benefit from.   

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Differentiation in Traits

EVF vs Optical

A DSLR (a Digital Single Lens Reflex) has an optical viewfinder whereas the mirrorless camera uses a digital screen; an electronic viewfinder. The advantage of an electronic viewfinder is that it lets you see changes to exposure on the fly. With a DSLR you only see the effect of exposure on an image after you have taken the photo. This makes it a little easier to get the exposure right first time with a mirrorless camera. However, most DSLRs also allow composition in ‘live-view’. This essentially turns the DSLR into a mirrorless camera where you control the camera and compose through the rear LCD screen rather than the viewfinder. In either regard, beginners might find it easier learning on a mirrorless camera or through the use of the rear LCD screen on a DSLR.

Up until very recently the disadvantage of an EVF was that there was/is a lag between pressing the shutter button and capturing an image. New cameras like the Sony A9 and A1, make this no longer an issue, but at a significant price. The new mirrorless cameras continue to shorten the gap  between pressing the shutter button and capturing the image. The new mirrorless cameras also don’t have ‘mirror blackout’. This is an effect when shooting with a DSLR that essentially blacks out the viewfinder as you take an image while the mirror flips up to allow the light to pass through to the sensor.

In certain scenarios having an optical viewfinder is easier, such as high frame rate photography of sport. Since you are viewing the world in ‘real-time’ through the lens, it is easier to follow action with the camera. Again the high-end mirrorless cameras have basically done away with this issue, but it is still an issue with entry-level and lower priced mirrorless cameras.

Another detraction from EVFs is that photographing in very low light situations can be problematic, even with the very best EVFs. The reason for this is that the viewfinder is dependent on what the sensor can ‘see’. In low light, the sensor has to ramp the exposure using high ISO, which in turn creates a lot of noise in the image. In extreme low light situations (photographing the stars, night sky, or also using low output modelling lamps in a studio), the noise in the viewfinder can make composition and focusing difficult.

For someone learning photography EVFs hold an enormous advantage over traditional optical viewfinders. This is that you can see the effect of exposure changes as you compose. Changing the exposure, white balance, or any of the image setting will affect the view you get, and hence the photograph you are creating. In a DSLR you can only see the affect after you have shot the image. With a mirrorless camera you see the effect while composing, and can make allowance for these changes while shooting.   

Cornelius Muller shooting on the tiny Fujifilm XT-2 while on a workshop in the Drkensberg. The small body and lenses of the mirrorless APS-C system make travel easy and painless compared to the larger Full-Frame DSLRs

The new Nikkor S 14-30mm f4 (for mirrorless) and the older, larger and heavier 16-35mm f4 (for DSLRs). The new lens is also sharper, but lacks the mechanical focusing of the older lens.

Size

The promise of mirrorless for many is the reduction in size and weight of mirrorless cameras due to the loss of the mirror. For the most part this is true. Mirrorless cameras are indeed smaller and lighter than their DSLR counterparts. This is particularly the case with the APS-C mirrorless cameras from Fujifilm, Sony and Canon, which are really small and light. The M43 Olympus cameras are truly tiny, which is why they are such popular travel cameras. Unfortunately physics rears its head as you get larger sensors, and larger sensors require physically larger glass elements in order to cover the full imaging circle of the sensor. This means that although we can get smaller camera bodies, the lenses themselves remain large (on Full Frame and Medium Format sensor cameras). The current penchant for super-fast glass (very large apertures) also means that the current generation of mirrorless lenses are enormous compared to the bodies they are mounted on (a notable exception are the range of small pancake lenses made by Tamron and Sony).



So mirrorless cameras can be smaller and lighter than DSLRs, but they aren’t always as small and light as they could be.

Batteries

Since a mirrorless camera uses an electronic viewfinder, it draws power from its batteries continuously, even when only looking through the viewfinder and not actively shooting. DSLRs go into a ‘sleep’ mode since they don’t need power to see anything through the viewfinder. As a result mirrorless cameras do chew through batteries more rapidly than DSLRs do. This isn’t really an issue though unless you need a battery to last long periods of time (timelapse photography, some sport photography, being away from power for prolonged periods of time). This has gotten better recently with the more expensive mid-level and professional mirrorless cameras. Entry-level mirrorless cameras continue to be plagued with the battery issue though. If you buy a mirrorless camera, make sure to get spare batteries basically (as one should anyway).

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Stabilization

Since the early noughties we have been getting increasingly better image stabilisation in our lenses, and now also in our cameras. With DSLRs stabilisation is relegated to the lenses that we use. Mirrorless, due to the loss of the mirror-box, has allowed stabilisation of the actual sensor (they build the sensor into a gyroscope basically). This means in theory that mirrorless lenses can be smaller, lighter and cheaper (unfortunately for the most part they are not, but we’ll get to that below). In a nutshell though, you get more stabilisation choices with mirrorless than with DSLRs.

As an added bonus, sensor based stabilisation has led to ‘pixel-shift’ technology. What this does is capture multiple images while shifting the sensor slightly to the left and right and up and down. The camera proceeds to stitch these images together to create a single file with a greater resolution than the sensor allows with a single capture. At the moment pixel-shift is available on some Sony, Olympus and Fujifilm medium format and Panasonic cameras.

The advantage for some photographers is that they can use small sensors like those in the Olympus OME series, but get results similar to the larger Full-Frame cameras. The downside is that you have to use it on scenes that are close to dead-still as any movement in the scene has the potential to create weird artefacts (ghosting etc).

As an aside, Pentax also offer in-body stabilisation and pixel shift shooting with their recent DSLR cameras. They are the only DSLRs that do so. Hasselblad also allow a multi-shot mode which shifts the sensor slightly between exposures and stitches the resultant images together. Pixel-shift can only really be used properly while on a tripod, of a subject that is not moving at all, so it’s not something that should make or break a camera purchase. At the moment neither Canon nor Nikon have implemented pixel shift, even though both do now have in-body image stabilisation on their mirrorless cameras.

A graphic from Olympus' marketing material showing the different movements (yaw, shift, roll and tilt) that can be counteracted with sensor shift.

Cost

If for nothing else, mirrorless is the future of photography since it is cheaper to manufacture cameras without a mirror than with one. There are fewer parts involved in the manufacture of the camera, less materials and more functions driven by the imaging sensor and the CPU, than by other sensors that used to be required by DSLRs. You’d be mistaken for thinking that because mirrorless cameras are easier and cheaper to produce than DSLRs, they would also be cheaper. Unfortunately you’d be wrong. Across the board mirrorless cameras are more expensive than their DSLR equivalents. This extends into the lenses as well incidentally, with the marque manufacturers of Nikon, Canon and Sony all producing lenses that are more expensive in the mirrorless mount than they are in the DSLR mount (the distinction is egregious in the new Canon super telephotos which literally just retool the mount for mirrorless).

If you are in search of a bargain, look at DSLRs as an option (particularly secondhand). If you have the means and want your equipment to be state-of-the-art and future proof, then look to mirrorless.

Conclusion

The most important thing to realise is that there is absolutely no difference in the image quality achieved between DSLRs and Mirrorless cameras. There are potential advantages to both systems over the other that can make shooting in different scenarios easier or more difficult. Moving from a DSLR to a mirrorless is not going to improve your images in any meaningful or even material way. Similarly, in buying your first camera, you are not losing out choosing one over the other. If you are a beginner photographer there is a possibility that it might be easier to learn photography using a mirrorless camera, but the argument can also be made that you will learn faster not using a mirrorless camera as you have to think a little more about settings and exposure (since you don’t see the setting changes real time in a DSLR like you do on a mirrorless).

For many the primary decision factor comes down to cost and size. Mirrorless is more expensive, but smaller usually than DSLRs. DSLRs on the other hand tend to be more affordable (relatively speaking) but are bigger and heavier.

It is important to remember that there is no difference in image quality between mirrorless and DSLR. Here Chris is shooting with a Nikon D810 and the other photographer with a Sony A7riii. The Sony has slightly more resolution, but the actual IQ will come down to lenses used, tripod technique and exposure control...none of which rely on being a DSLR or mirrorless.

DSLR vs Mirroless - Winners and Losers (said tongue in cheek)

	Winner	Loser	Tie
Cost	DSLR - Right now, feature for feature you will get better value for money with a DSLR. The equivalent DSLR is always cheaper than the mirrorless at the moment. Lenses are also significantly cheaper for DSLR than mirrorless.	Mirrorless is the trend, but also has a price tag to match.
Size	Mirrorless - body size is smaller and lighter than DSLRs for the simple fact that there is no mirror box. The big BUT is that the lenses are often huge.	DSLRs, particularly high end ones are big and heavy. Even the small entry-level cameras are bigger (although not necessarily heavier) than similar mirrorless versions.	Due to the size of the lenses this is technically a draw between DSLR and Mirrorless - the exception being the APS-C and M43 models which are genuinely small and light
Lens Choice	DSLR (with a caveat) - there are decades worth of lenses available in the mount of choice for each DSLR. But, it won’t be long before mirrorless has as many options.	No real loser	DLSR used to be the winner here, but this is now a tie in reality. If there isn’t a lens in the native mount there are adapters for it.
Auto Focus	DSLR, but only at the Low end, with cameras like the Sony A9 now being as good as the flagship cameras from Nikon and Canon	No real loser	For the most part this is actually a tie at the top end of cameras.
Manual Focus	Mirrorless - The focus aid available to mirrorless cameras make focusing manually extremely easy and accurate. No more missed shots!	Definitely DSLR, despite the optical viewfinder.	-
Exposure Control	Mirrorless - The EVF allows for exposure changes to be seen in real-time, making exposure choices very easy and quick to make.	DSLR - You only see the effect after you have take the shot, unless you use live-view which is as if you were using a mirrorless	-
Battery Use	DSLR - minimal battery usage and small batteries can literally last for days	-	It’s not a tie really, but battery performance should not be a deal-breaker anymore. Buy more batteries as they are usually relatively inexpensive and don’t weight much.
Sports	DLSRs in the budget range. The ability to follow action in an optical viewfinder along with a mature focus system means DLSRs still hold their edge here.	Apart from the very latest high end models, there is viewfinder lag when shooting continuously and autofocus performance in the lower models is not as good as their DSLR counterparts.	This is only a tie in the high end cameras that cost a bomb.
Landscape	Mirrorless - this would be a tie but for the fact that manual focus is important in landscape photography, and mirrorless makes this easier. Mirrorless is also smaller (with the right lenses) so easier to carry. High end mirrorless also has higher resolution, and some lower end mirrorless have pixel shift.	-	-
Reportage Theatre	Mirrorless - smaller, lighter and silent shutter	DSLR - heavy, and has loud clunk noise when the mirror moves up and down.	-
Wildlife	-	-	Overall a tie. The optical viewfinder makes composition easier with a DSLR, but the newer eye-autofocus on mirrorless makes accurate autofocus easier with a mirrorless.
Macro	-	-	Effectively a tie - An optical viewfinder is great in low light, but the focus aids from a mirrorless are also great for macro photography.
Night and Stars	DSLR - an optical viewfinder will allow you to see anything your vision can.	Mirrorless - An EVF ramps the signal from the sensor to see in the dark, meaning that the viewfinder will eventually just show noise instead of a picture - it’s getting better though.	-