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5 August 2021

How we test DSLR and mirrorless cameras

Find out how we test DSLR and mirrorless cameras to separate those that put you in a position to take fantastic photos, from the duds that let you down.
Jake Massey
How we test1

A mirrorless or DSLR camera is a big investment – you’re not just buying a camera, but investing in a system of lenses and accessories that you may be using for many years to come. 

That’s why we recommend the cameras you can trust to help you take great pictures and support you in your photography

What makes a Best Buy DSLR or mirrorless camera?

We look for sensors that make the most of the light in every scene, and the features and controls that enable you to get a brilliant photo in an instant, but also give you the creative power when you want it. 

While we want faster shutter speeds, higher ISO settings and a fast, precise auto-focus, we don’t forget about the basics. What is the kit lens like? Is it easy to grip? How hard is it to replace the batteries? 

A DSLR or mirrorless camera must score 76% or higher to earn our Best Buy recommendation. DSLR or mirrorless cameras that score 45% or lower are Don’t Buys, because we think they’re best avoided.

How is the Which? test score calculated

We conduct around 450 tests per camera; every DSLR and mirrorless camera goes through exactly the same tests, combining assessments from image-quality experts with rigorous technical lab tests. We ensure that every camera review answers all the key questions you might have, including:

  • Does this DSLR or mirrorless camera take great photos?
  • How easy is this DSLR or mirrorless camera to use?
  • How good is the monitor and/or viewfinder?
  • Does this DSLR or mirrorless camera shoot great video?
  • How effective is the built-in flash?
  • Will its features help me take better photos?

All the tests above contribute towards a total test score, which enables us to pull the best and worst cameras from the pack. We don’t figure price into the equation. The total score breaks down as follows:

  • 45% image quality
  • 30% ease of use
  • 10% viewfinder & monitor performance
  • 10% video/audio quality
  • 5% flash (when applicable)

Don't settle for anything less when it comes to image quality - find a superb DSLR or mirrorless camera that takes first-class stills and videos from our Best Buys.

Mirrorless cameras photographing

Our key testing criteria

Below are our key testing categories and how we evaluate each one.

Does this DSLR or mirrorless camera take great photos?

With DSLR and mirrorless cameras, photo quality is paramount. We take photos in a range of conditions, including in bright outdoor natural light, indoors and in low light. And we try the camera with different settings, using the bundled kit lens at both its wide-angle and telephoto settings, and using the camera in both automatic and manual modes. 

We also measure image resolution and look for potential problems, such as distortions, with the camera at different settings. 

Our Best Buy DSLRs and mirrorless cameras produce great photos whether you’re shooting inside or outside, in sunlight, twilight or under artificial light.

How easy is this DSLR or mirrorless camera to use?

DSLRs and mirrorless cameras may be designed for more advanced photography, so will inevitably be more complex than a simple point and shoot compact camera, but we still expect them to have quick and intuitive controls, well-placed buttons and dials, a comfortable grip for steady shooting, logical menus and a good range of features.  

We also look at:

  • How easy it is to insert a memory card or change the batteries
  • How fast the camera is to start up
  • How quickly the shutter reacts when you press the shutter release button; is it quick enough to make sure that you get the shot you want, and is there enough feedback to know when you have your subject in focus and ready to shoot? 
  • How quickly the camera can rattle off a burst of shots, so that you don’t miss the perfect fast action or wildlife photo.                                                                

How good is the monitor or viewfinder?

Most DSLRs come with an optical viewfinder as well as a monitor; you can use the monitor both to frame images and to review photos and change settings. Some mirrorless cameras rely solely on monitors, though others also have electronic viewfinders (visit our guide on DSLR vs mirrorless cameras for more on the difference between optical and electronic viewfinders).

We check both carefully to see whether they provide the clarity, field of view and detail you need to help you compose your photos and make creative decisions. We also assess them both in low light and bright sunlight, to ensure that our Best Buys can be used in any situation.

Does this DSLR or mirrorless camera shoot great video?

We set each DSLR and mirrorless camera to shoot video of two different scenes at a range of different quality settings, looking for whether it can capture fine detail and colour in clothing or objects, while checking how well it handles fast movement. We pan the camera around to see whether the picture holds up, or whether it becomes jerky. 

We also assess and rate the audio captured by the built-in microphone, listening carefully to see whether any noise is picked up from the auto-focus or the buttons, and whether the sound is clear and rich or dull and muted.

How effective is any built-in flash?

Where a DSLR or mirrorless camera has a built-in flash we put it through its paces to see how well it adjusts its brightness for different conditions, so that you don’t end up with shiny-looking skin in portraits or underexposed photos when you shoot indoors. 

We also take a photograph at different distances, from close up to more than 10m away, to see how the flash behaves at different ranges. Does it go too bright close up, or does it lose its power when at a distance? Do any unwanted reflections from it creep into the shot?

Will its features help me take better photos?

Manufacturers often claim that certain camera features will help you take better photos. We put those claims to the test. 

We test face-detection features to see whether they help you take well-exposed, sharp photos of people – alone and in groups. We also test image-stabilisation features by putting the camera on a vibrating platform, simulating a pair of shaky hands.

Digital camera security testing

Like many modern gadgets, digital cameras increasingly have internet-connected features. Digital security is paramount, so we carry out tests to ensure that cameras and their related apps are secure and responsible with your data. 

These don't feed into our overall test scores, but if we identified a significant problem, we'd let you know and it might impact on a camera's Best Buy status. 

Camera app privacy and security

For some time, camera manufacturers such as Canon, Nikon and Sony have been providing dedicated apps for use with your camera. These apps are designed to enhance how you use your camera, for example, by controlling your camera remotely or by automatically backing up photos and videos to your phone or tablet.

No camera apps should transfer any personal data without your permission. They should also have high standards of security to protect them from vulnerabilities, including password quality controls, appropriate encryption, and authentication to prevent the information you transmit to the app from being hijacked. 

We also check that apps only request information they need to provide you with a service. When apps ask for permissions they don't have functionality for, or when they seek to harvest excessive amounts of personal data, we talk to manufacturers to find out why. We also detect the location of the servers your data is being transmitted to.

We haven't found any cameras or related apps that misuse your data or expose it to needless risk, but we will keep testing them so you can be assured that the information you give away is protected.