What is a Mirrorless Camera? | A Beginner’s Guide

Mirrorless cameras stormed the market by 2013 when major manufacturers like Sony, Nikon, & Fujifilm entered the scene. Panasonic Lumix and Olympus PEN models first introduced mirrorless systems as a photography camera. Mirrorless techniques were already in use for viewfinder cameras. Mirrorless cameras made a giant leap from a moderate camera experience to the front face of photography within a few years. Now let’s understand what a mirrorless camera system is, and how it works.

What is a Mirrorless Camera?

A mirrorless camera is a type of camera that eliminates the use of a mirror from the conventional SLR model. The key to the development of mirrorless cameras is advancement in digital electronics in the early 21st century. There are fixed lens Point-and-Shoot mirrorless cameras, and then the mirrorless interchangeable-lens cameras (MILC).

An SLR or a DSLR camera uses a mirror, along with the help of a pentaprism, in front of the sensor to project the image to an optical viewfinder. As the name suggests, mirrorless cameras do not have a mirror for the optical viewfinder. Instead, they have an electronic viewfinder(EVF). The sensor relays feed directly into the EVF. Before explaining the working of any camera it is crucial that you understand the individual components that make up a camera system.

Components in a Mirrorless Camera

A mirrorless camera build is almost similar to that of a DSLR. However, the viewfinder & autofocus systems are different. You are already using a mirrorless camera if you use smartphone cameras, or point and shoot models. Let’s take a look at the components that form a mirrorless camera.


The sensor is the most vital part of any camera. When exposed to light, the sensor converts the light into digital signals. Modern cameras use CMOS sensors, while the older ones used CCD sensors. Also, there are full-frame sensors and APS-C sensors in the market.

Image Processor

Once the light data is converted to digital signals in sensor, the image processor processes this data to produce a JPEG or RAW for images, or a video file like MP4 or even RAW videos. Image processors also determine a lot of other factors such as readout speed, focus performance, etc.


Modern mirrorless cameras feature both mechanical and electronic shutter. Check out our article on Shutter Speed in order to understand how a shutter works in modern cameras. The electronic shutter is predominant in mirrorless cameras because the sensor is always open.

While using a mechanical shutter in mirrorless cameras, the shutter first closes the sensor when the shutter release button is pressed. Then, the shutter exposes the sensor and then closes again, and later comes back to the original position. Why bother using it at all? Mechanical shutters tend to induce a lesser rolling shutter effect at higher shutter speed than an electronic shutter. Even with this amount of mechanical movement, beasts like Canon EOS R5 support a shutter speed as fast as 1/8000s and a continuous drive speed of 12fps in the mechanical shutter mode. And the same camera can burst a whopping 20fps continuous drive speed in the electronic shutter mode.

An electronic shutter is a silent mechanism. Unlike the mechanical shutter than involves motion, electronic shutters turn off and on the sensors in order to simulate the effect of a shutter. However, the chances of the rolling shutters are higher in electronic shutters.


Lack of the mirror and pentaprism in mirrorless cameras provide extra space as well as reduce the flange length in a camera. Distance between the sensor and where the lens is mounted is called flange length. A decreased flange length decreases the camera size. It is also important to consider your hand size while choosing a camera. If you have larger hands find a camera that fits your grip. You don’t want to feel uncomfortable with a small camera in your hand. The same applies to everyone, find what suits you.

The extra space allowed manufacturers to include In-Built Image Stabilization (IBIS) into mirrorless cameras. IBIS tracks the shift in sensor position while taking a photo and compensates for the movement. This allows the photographer to take better photos. Kindly note that IBIS is an exclusive feature of mirrorless cameras. If technology allows, even DSLRs may come equipped with IBIS.


The viewfinder allows the photographer to compose the image before capturing a photo. In DSLRs, the combination of mirror and pentaprism allowed the photographer to see exactly what the sensor sees. Unlike DSLRs, mirrorless cameras use a live feed from the sensor and project it to the high-resolution EVF. EVF has a better display quality than the rear monitor.


Conventional DSLRs have a dedicated autofocus(AF) sensor whereas mirrorless cameras use the camera sensor for AF functionality. Initially, mirrorless cameras didn’t perform well in object tracking. In effect, it performed poorly in action capture. However, modern mirrorless cameras boast a hybrid AF system with phase shift and contrast shift AF, unlike the initial models with only contrast shift AF. In contrast AF, only the contrast between adjacent pixels is analyzed to drive the focus motor in the lens. On the other hand, phase-detection AF calculates the phase difference between the incoming light signal to account for length. This way, phase-detect AF provides a better AF function and supports incredible live tracking.

How does a Mirrorless Camera work?

Now that we have explained the basic structure of a mirrorless camera lets take a look at how it works. Like any camera, light falls into the aperture of the lens to finally reach the sensor inside the camera body. When the shutter-release button is pressed, either electronic or mechanical shutter exposes the sensor to incoming light. The image processor then writes out the data from the sensor into a viewable format, like JPEG or RAW. This is a very simple explanation of a very complex system. Note that a large number of electronic circuitry working in synchronicity gives the final image you see on the camera.

The Weaknesses

Even though the mirrorless cameras are closing in tight with DSLRs in terms of performance, they do have some disadvantages. Reducing the body size limited the space for the battery in mirrorless cameras. Initial models had poor battery life. However, things are changing as batteries are getting better day by day. Poor performance in low light conditions is another issue that mirrorless cameras face. But now we have full-frame mirrorless cameras like Sony a7S III in the market that are praised for their exceptional and incomparable low light performance. EVF is a key feature of mirrorless cameras. However, EVF can be unreliable while capturing very fast action, like racing. The processor lag and refresh rates of the screen limit the performance of EVF.

Having discussed all that, please be informed that all these disadvantages are due to the limitations of the present technology. Soon enough, things will change for the better. Make sure that you understand your options before choosing a camera.

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Adarsh R

A blend of a photographer, a movie lover, and now a writer.