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What Is A Mirrorless Camera?: A Complete Guide About All You Need To Know About Mirrorless Cameras


Jo Plumridge

This article is an extract from Issue 73 of Photography Masterclass Magazine
Image of mirrorless camera
Photo By: Mojtaba Mosayebzadeh
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Mirrorless cameras have been around for a while now but they’re getting a lot of press at the moment with Canon and Nikon entering the full-frame mirrorless market with Canon’s EOS-R and Nikon’s Z6 and Z7. Alongside Sony’s A7 range, there is now a choice of top-end mirrorless cameras available on the market. So, for those of you trying to figure out exactly what is a mirrorless camera, here’s our expert guide.

Overview: What is a Mirrorless Camera?

The clue is in the name! Mirrorless cameras don’t have a reflex mirror-like DSLRs. In a DSLR the mirror reflects the light up onto an optical viewfinder, whereas in a mirrorless camera there is no optical viewfinder. Instead, the imaging sensor is constantly exposed to light, giving a digital preview of the image on either the LCD screen or through an electronic viewfinder (EVF). The term mirrorless is actually a little disingenuous as it relates to mirrorless digital cameras with interchangeable lenses (ILCs). However, there are and have been many other styles of camera that haven’t had a mirror. But in modern terminology mirrorless describes ILCs. You will find that mirrorless cameras are significantly smaller and lighter in construction than DSLRs.

The Ins and Outs of the Mirrorless Camera

Photo By: Michael Soledad

You might be thinking that because mirrorless cameras are smaller than DSLRs they can’t have the same sensor sizes. But actually they can! As with DSLRs, you’ll find both crop frame and full-frame options and some manufacturers such as Fujifilm are taking it further and producing medium frame sensors. It certainly seems that manufacturers are investing time and effort in pushing the boundaries of mirrorless technology.

One of the areas where mirrorless cameras excel is with video. The EVFs can also be used in video mode and the manufacturers have also put a lot of effort into building in 4K capabilities to the cameras. Autofocus capabilities have also improved immensely on mirrorless cameras. Many mirrorless cameras also have touchscreens, meaning that you can literally ‘tap’ a point on the screen to focus on. However, good as the systems are I don’t believe that they can currently compete with the traditional DSLR AF systems. This is particularly noticeable when it comes to low light and tracking moving objects. However, the systems are improving all the time and it’s quite possible that they will surpass DSLRs one day.

Battery life on modern mirrorless cameras is excellent. But if you come from a DSLR background, you’re going to notice that the batteries don’t quite last as long. This is because of the constant use of the sensor and either a live view LCD or EVF.

Mirrorless cameras, particularly at the top end, have controls, menus and dials that are very similarly laid out to DSLRs. If you’re already using a DSLR and decide to switch to the same manufacturer’s mirrorless version, you should find the transition smooth.


Mirrorless camera lens

A lot of the mirrorless cameras have proprietary lenses that have been specifically designed for that specific system. Smaller mirrorless cameras can get away with smaller lenses, which all helps to keep the weight down. Of course, a 300mm lens is still going to be a weightier addition, but it is relative to the lenses found on DSLRs.

However, if you’ve been using DSLRs for some time, it’s likely that you’ll have built up a collection of lenses. Fortunately, all the major manufacturers offer converters that allow you to use your old lenses on mirrorless cameras. Like DSLRs, mirrorless cameras use a bayonet-style mount for attaching different lenses. And, as mirrorless is becoming increasingly popular, third party manufacturers are starting to produce specific lenses with different mounts, meaning that there’s a huge range of lenses to choose from.

Photo By: Reinhart Julian

Advantages and Disadvantages

As with most things in life, there are advantages and disadvantages to the mirrorless system. Let’s have a look at some of the key points:


  • Mirrorless cameras are significantly smaller and lighter in construction than DSLRs but still have the same sensor sizes.
  • Proprietary lenses are also smaller and lighter than DSLR lenses.
  • The EVF shows virtually 100% of your image and gives you a preview of how the final image will look. If you increase or decrease your shutter speed or aperture, for example, the results will show on the EVF. You can also electronically adjust the brightness and contrast of an EVF.
  • Modern mirrorless cameras have sensitive chips and can use the same sensors as DSLRs meaning that image quality is excellent and favourably comparable.
  • Video quality on mirrorless cameras is excellent, with many models having 4K and Ultra HD capabilities.
  • Mirrorless cameras have the ability to shoot quickly and silently, with excellent fps rates.


  • Battery life isn’t as good on mirrorless cameras, due to the EVF and live view LCD as well as the constant use of the sensor.
  • Autofocus, whilst improving all the time, is not quite as good as that of DSLRs – particularly in low light and when tracking subjects.
  • The EVF struggles in low light and when tracking subjects, with the preview slowing down and often becoming grainy and jerky. This is because the mirrorless camera has to slow down the speed at which it captures images to grab more light, but still has to show you a moving preview.
  • There aren’t as many proprietary lenses available for mirrorless cameras and, whilst you can use DSLR lenses with a converter this adds to the weight of your mirrorless system.
Photo By: Thom Bradley

In Conclusion

Hopefully, this article will give you a better understanding of mirrorless cameras and their capabilities, as they become a more and more popular option.

Video: Mirrorless vs DSLR Cameras

by Tony & Chelsea Northrup

In this video, the topic is mirrorless vs DSLR and the differences between them

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