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What is a Mirrorless Camera? (6 Things You Should Know)

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If you are shopping for a new camera, the hype of the moment is the mirrorless camera. But what is a mirrorless camera? And why should you buy one?

This article will discuss six things you should know about mirrorless cameras. Have a read and then decide if mirrorless is the way to go.

Sony a7 III
Sony A7 III
This full frame mirrorless camera is perfect for experienced photographers, offering high resolution and fast autofocus for stunning shots.
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What is a Mirrorless Camera?

So what is a mirrorless camera? As the name suggests, mirrorless cameras have no mirror. This is unlike digital single reflex cameras, better known as DSLRs.

The mirror has been used since the 1950s. So why change it? There are at least three good reasons to remove the mirror:

  1. No longer a delicate and complicated mechanism
  2. Reduces camera shake
  3. It makes for a more compact and light camera body

An electronic viewfinder (EVF) replaces the mirror system. This is a small, high-resolution LCD screen.

The image below shows an old Olympus OM-1 35 mm film camera and a modern Olympus OM-D EM-5 Mark II.

Diptych showing the mirror in the Olympus OM-1 SLR camera (left). On the right no mirror is present the interior of the modern Olympus OM-D EM-5 Mk ii mirrorless camera
A mirror in the Olympus OM-1 SLR camera (left). No mirror in the modern Olympus OM-D EM-5 Mark II mirrorless camera, and the sensor is visible (right).

6 Things You Should Know About Mirrorless Cameras

A small disclaimer… I am a long-time mirrorless camera photographer and enthusiast. But if you are going down the mirrorless camera road, you should know that it’s not all roses.

6. Mirrorless Cameras Are Smaller and Lighter Than a DSLR: The Size Myth

The mirror (with all the other related parts) is not there anymore. This makes the camera body smaller and lighter than DSLR bodies. This is particularly good for pro-graded gear.

  • The Myth: A mirrorless camera is a perfect camera to bring everywhere. They are small and light. If you value portability, you should buy one of these cameras over classic DSLR ones.
  • The Truth: This is historically accurate. The first mirrorless cameras were Panasonic and Olympus cameras. They had no electronic viewfinder (or it was optional). They also sported a Micro Four Thirds (MFT) sensor. This is half the size of full frame sensors.

But what about today’s mirrorless cameras?

One of the first Olympus mirrorless cameras: the EPL-2 with MFT sensor and no EVF.
One of the first Olympus mirrorless cameras. The Olympus EPL-2 with MFT sensor and no EVF.

A Comparison of Old and New Olympus Mirrorless Cameras

Olympus is still working with the MFT format. What about competitors like Fujifilm, Sony, Pentax, Nikon, and Canon? They’re using APS-C and full frame sensors instead.

But the size of a full frame sensor should not change the size of the camera body significantly. Right? True, but these cameras are ILC cameras. This stands for “interchangeable-lens cameras.”

The size of a lens determines the amount of sensor that is illuminated. This means it affects the size of the image the lens projects on the sensor.

Very compact and lightweight interchangeable lenses can illuminate MFT sensors. But for full frame sensors? They need lenses as big as those used by DSLR full frame cameras.

The Olympus EPL-2 with the 14-42mm lens - mirrorless camera facts
The Olympus EPL-2 with the 14-42 mm lens (28-84 mm equivalent focal length on full frame, or EFL) is a classic kit lens. The SD card is there to show the scale of size.

And there’s another drawback. The camera body is nice and small. But this means that the camera-lens system is unbalanced on the lens side.
This is tiring and annoying when photographing handheld with big lenses.

If you need an adapter, things get even worst. The heavy lens is pushed further in front of the camera body. This will make an already unbalanced system worse.

Top view comparison of a 28mm wide angle lens on the old OM-1 (right) and on the OM-D EM-5 Mk ii (left).
A top-view comparison of a 28 mm wide-angle lens on the OM-D EM-5 Mark II with the necessary adaptor (left) and on the old OM-1 (right). The lens sticks further out with the adaptor, moving the weight far from the camera body.

This also reduces the portability of a full frame mirrorless system. What you gain is only on the size and weight of the camera body.

But to make things more ergonomic, the bodies are often not made as small as they could be. Dedicated accessories even exist to make the body larger and easier to hold.

Below is a comparison between the Olympus OM-D EM-5 Mark II and the EPL-2. You can see them with and without the accessory power grip for the OM-D.

Diptych comparison between the EPL-2 and the OM-D EM-5 Mk ii with and without power grip.
Comparison between the EPL-2 (small) and the OM-D EM-5 Mark II (large) with and without a power grip.

Removable battery grips are an interesting solution. It lets the camera stay small when paired with small, lightweight lenses. And ergonomics are improved when using heavy and long lenses.

As you see, the argument about size and weight is not particularly good. That’s especially true if you care about portability.

If this is your case, try a high-end bridge camera like the Sony Cyber-shot RX10 IV from the Sony RX10 family. Add a fast superzoom lens if needed. It can be a better solution.

Diptych of the OM-D EM-5 Mk ii with power grip Vs the Sony RX10 bridge camera - mirrorless camera tips
The OM-D EM-5 Mark II with a power grip vs the Sony RX10 bridge camera.

5. Mirrorless Cameras Are WYSIWYG Cameras

Mirrorless cameras have a much stronger advantage over DSLRs. They arewhat you see is what you get” cameras. And this will make you improve faster as a photographer.

How? They always use the electronic viewfinder (or Live View) to show you what the mirrorless digital camera sees. Plus, you see the effects of changing camera settings (shutter speed, aperture, ISO). And you see these in real-time.

The video below shows the effects of changing the shutter speed in real-time.

A gif showing settings applied real time to the scene displayed on the LCD or EVF.
The settings are applied in real-time to the scene and displayed on the LCD or EVF.

This will help you understand the exposure triangle, aperture, shutter speed, etc. It will also make it easier to work in manual mode, particularly for photography beginners.

Another benefit? It will help you to manual focus in the dark. This is especially true if you are trying astrophotography, nighttime, or interior photography.

Overexpose the image to brighten the scene enough that it will be easy to focus. Then return to the proper settings for taking the photo.

4. Mirrorless Cameras Don’t Suffer From Light Leakage During Long Exposures In Daylight

If you have an optical viewfinder, light can enter your camera from it. In the photo below, the image you see on the mirror comes from what the viewfinder sees.

Light from the optical viewfinder of my OM-1 forms this image on the mirror.
Light from the optical viewfinder of my OM-1 forms this image on the mirror.

Light leakage from the viewfinder is not usually a problem. But if you’re doing long exposures, you should cover it. Your eye will not block it. Light can creep into the body, ruining your image.

If you look at the strap that came with your camera, you will find a small black piece of soft rubber. That is what your camera maker wants you to use to close the viewfinder during long exposures.

The cover for the optical viewfinder of a Canon DSLR.
The strap cover for the optical viewfinder of a Canon DSLR.

Since mirrorless cameras have no optical viewfinder, you don’t have to do this. And you can’t do anything even under harsh midday sun (and I do infrared photography with a mirrorless…).

3. Battery Life is Poor With a Mirrorless Camera: The False Power Problem

Mirrorless cameras drain their batteries faster than DSLRs. Even if the rear LCD is OFF, it uses energy to power the electronic viewfinder.

On average, the battery life for entry-level mirrorless cameras is about 300 shots. The high-end Sony a7 III camera reaches an astonishing 700 shots.

Entry-level DSLRs also allow you to take around 400 shots with a charged battery. You can take up to 1000 shots with the pro models like the Canon 80D.

People seem to make a big deal out of that. To me, this is a false problem.

How many of us shoot more than 300 images without the possibility of replacing the battery with a spare one? Do we need to shoot 900 photos with a single battery?

Also, as I said, power grips are available for many high-end mirrorless cameras. These allow you to use two batteries at the same time.

I do astrophotography with my Olympus OM-D EM-5 Mark II. I am out there at night, in the cold or humid weather.

Even when taking 200-plus images of the starry sky, I never run out of battery. Even without using the power grip.

2. Mirrorless Cameras Have Fewer Accessories Than DSLRs

That may be true, at least for MFT mirrorless cameras. Third-party lenses are scarcer than in the DSLR world. There are only some from Sigma (three lenses), Tamron (one lens), and Samyang/Rokinon (less than three lenses).

Lens adaptors are usually available to adapt lenses with a different lens mount. You can pair mirrorless cameras from Canon and Nikon with existing DSLR lenses.

There may also be fewer flash and remote shutter products than those available for DSLRs. Once again, though, this is something of a false problem.

Makers of camera accessories follow the market. And the mirrorless market is growing by the minute. They have started building dedicated accessories and lenses.

1. “Pros Don’t Use Mirrorless Cameras”: The Quality Myth

What’s the most common argument against mirrorless cameras? “Professional photographers are only using DSLRs.”

That’s not true. Many world-renowned photographers have switched to mirrorless.

One of the first to do so was travel photographer Trey Ratcliff. Other notable photographers include Andy Mumford and Phil Norton.

Image quality is about the lens and sensor (and electronics) combination. The mirror has no role in that. If you want to give the mirror a role, it’s the bad guy slapping around and blurring your long exposures.

There are many pro-graded lenses for mirrorless cameras. So image quality is not an issue.

There are two very practical reasons why most pros are still using DSLR cameras:

  1. They have spent a little fortune on photography equipment. So switching is expensive.
  2. People tend to associate small cameras with amateurs. And big, bulky DSLRs with large lenses are equated with professionals. The thinking is that if you are a wedding photographer with a small Olympus PEN-F, you will not attract many customers. And those you will get will give you weird looks.


We hope we’ve answered the question, “What is a mirrorless camera?’

If you are in the market for a new camera and you are interested in going mirrorless, here is what you should know:

  1. Mirrorless cameras are not always the small and light package people say. The most compact ones are MFT mirrorless cameras. Their smaller sensor can be illuminated with small, compact lenses.
  2. A mirrorless camera can make you become a better photographer. You will be able to see the effect of your settings in real-time.
  3. Yes, a mirrorless camera has shorter battery life than a DSLR. But do you really need continuous shooting of more than 300 photos without changing the battery?
  4. There is a larger number of camera accessories and third-party lenses for DSLRs than for mirrorless cameras. But the situation is changing as mirrorless camera bodies gain more and more market share;
  5. Image quality is on par with that of DSLR cameras. Many pro photographers (particularly those in travel photography and landscape photography) have completely switched to mirrorless camera systems.

For more great information, check out our great guide to the different types of digital cameras.

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