Viewfinder vs LCD Display

Most Canon EOS cameras offer two ways of composing images: using the viewfinder or the LCD screen on the back of the camera. Which you use depends upon the subject, the shooting conditions and your personal preferences. But are there any advantages to using one or the other? What are the differences between them? And are all viewfinders the same?

The key difference between a DSLR and a mirrorless camera is implicit in the names: a DSLR (Digital Single Lens Reflex camera) is so called because it has a reflex mirror. This reflects light coming in through the lens up into an optical viewfinder (OVF) via a pentaprism or pentamirror that ensures you see the scene the right way round through the camera's eyepiece. This means that with an OVF you are seeing what the lens sees, reflected but unprocessed.

In a mirrorless camera, an electronic viewfinder (EVF) uses the information from the imaging sensor to display an image on a small LCD or OLED screen. This means that an EVF shows the image that the sensor outputs, which can be subtly or sometimes significantly different from the view through the lens.

While some photographers like the natural view offered by an optical viewfinder, an electronic viewfinder brings the advantage of being able to see the effect of the exposure, white balance and Picture Style settings being applied. If you apply the Monochrome Picture Style, for example, the image you see in the EVF will be mono, while with an OVF it will remain colour. This means you can use the image in an EVF to assess whether your settings suit the scene and to be confident you will get the result you want before pressing the shutter button. That's especially helpful if, for example, the subject is backlit and you might need to use some exposure compensation.

In this way, an EVF is especially useful for relatively inexperienced photographers, because it enables you to see the effects of camera settings at the shooting stage, not just assess them afterwards. For many, it makes photography more intuitive.

Another advantage of an EVF is that it can compensate for low light levels, which means you always have a clear view of the subject. Conversely, with an optical viewfinder you're seeing the scene with the ambient light level, which means that in dark conditions it can be difficult to compose a shot or to focus.

On the other hand, because the image you see in an EVF has to be processed before it can be displayed, all EVFs suffer from some degree of lag. Although the latest mirrorless cameras such as the EOS R5 have EVFs with a refresh rate of 120fps and the lag is only a matter of milliseconds, this can still matter if you're shooting fast-moving action and split-second timing is critical. As technologies continue to develop, the lag is likely to get shorter and shorter, but an OVF works at the speed of light, which means in effect no lag at all. For this reason, many photographers shooting sports, wildlife or other subjects involving fast action still prefer a DSLR.

In addition, when you're using an EVF you're actually looking at a small screen, and even though this has a very high refresh rate, an OVF can be more comfortable over a long period of usage. This means that if you're shooting wildlife or sports where you have to keep your eye to the viewfinder for a very long time waiting for the action to happen, an OVF could be preferable.

With a mirrorless camera, the camera uses exactly the same technology to display an image in the viewfinder as on the LCD on the back of the camera. This is not the case in a DSLR, but it is still possible to compose images on the rear screen in what is known as Live View mode. When you switch a DSLR to Live View mode, the reflex mirror is lifted out of the way and the shutter opened. Light can now pass through to the CMOS sensor, where the image is formed, and this is displayed live on the rear LCD display.

When a DSLR is in Live View mode and its exposure simulation feature is activated, you not only see what the sensor is seeing, but you also get an accurate preview of exactly what the image will look like before you press the shutter button. In this way Live View works just like using a mirrorless camera.

When you use the viewfinder on a DSLR, it's not just the display technologies that differ from Live View – the camera also employs separate, dedicated autofocus, exposure metering and white balance sensors. When it's switched to Live View mode, a DSLR uses the imaging sensor to gather this information – just like a mirrorless camera.

Since the introduction of the EOS 70D in 2013, Canon DSLRs have featured Dual Pixel CMOS AF technology. This enables on-sensor phase-detection autofocusing, which means that modern Canon DSLRs can focus as quickly in Live View mode as they can when the viewfinder is used. Canon EOS M series and EOS R System mirrorless cameras also have Dual Pixel CMOS AF technology, and it's employed for focusing whether the image is composed in the viewfinder or on the LCD screen on the back of the camera.

Whether you're shooting with a DSLR or a mirrorless camera, there are times when it's easier to use the camera's viewfinder rather than the LCD screen, and vice versa. For example, it's usually easier to hold the camera steady when it's held to your eye because it's braced against your face. It's also easier to follow a moving subject in a viewfinder than it is on a screen with the camera at arm's length.

However, when you're shooting landscape, still life, macro or architectural photography with the camera mounted on a tripod, the larger view provided by the LCD screen is extremely helpful. Similarly, when you want to shoot from above or below head height or at an angle, it's very convenient to frame the image on a tilting or vari-angle screen instead of trying to use the viewfinder.

It's also very helpful to use the LCD screen when you're focusing manually because the Live View image can be zoomed in to 5x or 10x magnification. This provides a very detailed view of any part of the image, making critical focus adjustments much easier.

On the EOS 90D in Live View mode and on mirrorless cameras including the EOS R5, EOS R6, EOS R, EOS RP, EOS M6 Mark II and EOS M50 Mark II, you can also enable Manual Focus Peaking (MF Peaking), a visual aid to show which parts of the image are in sharpest focus. In theory, areas in focus will coincide with the greatest contrast, so the image is evaluated for contrast and these areas are highlighted on the display in a bright colour of your choice. You can see the highlighted areas of the scene change as you change the focus.

Bear in mind, however, that using your camera's rear screen for extended periods will have an impact on battery life. Using Live View on a DSLR is also not recommended when you want to take fast bursts of shots, because it will usually reduce the continuous shooting speed. At the other extreme, if you're shooting an exposure that lasts for multiple seconds or minutes, an optical viewfinder can cause a particular problem: stray light can enter the viewfinder and interfere with the exposure. To prevent this, use the eyepiece cover provided on your DSLR's strap.

EOS cameras with an EVF have a proximity sensor that will automatically switch from the rear screen to the viewfinder when you raise the camera to your eye (although you can optionally disable this).

An EOS camera's viewfinder displays essential information such as the focus point and the exposure settings. With a mirrorless camera and a DSLR in Live View mode, it's sometimes also possible to see other information such as the white balance and Picture Style setting or the metering mode (evaluative, spot, centre-weighted or partial metering).

On a mirrorless camera or a DSLR in Live View mode, press the INFO button to cycle through the available display settings: image only, image with basic information, image with full information and image with live histogram. The amount of information that's visible can be tailored to your preferences using the Shooting Info Display or Info button display options settings in the camera's Setup menu.

The live histogram helps you assess the brightness of the scene and evaluate how the exposure settings affect it, in a way that you could otherwise do only by reviewing the image post-capture. You can see the graph move as the exposure settings are adjusted, helping you avoid burnt-out highlights or clipped, featureless shadows.

On cameras that feature an electronic level, this can also be overlaid on the Live View display of a DSLR or mirrorless camera. In some cases there's the option to show a level in a DSLR's viewfinder.

It's also possible to activate a grid view via the camera's Setup menu. This can be set to display a 3x3, 6x4 or 3x3 and diagonal grid on the screen when the camera is in Live View mode, and in some DSLRs in the viewfinder. This is a helpful visual aid that makes it easier to align objects in the scene, avoid tilted horizons and create pleasing scenes conforming to the compositional principle known as the Rule of Thirds.

The depth-of-field preview button, found on the front of some EOS DSLRs next to the lens mount, is useful for checking what parts of the scene are in focus at the current focus and aperture settings. It can even be used in combination with the magnification functions to give a very clear idea of exactly what will be sharp.

EOS cameras can adjust the brightness of an electronic viewfinder and the rear LCD screen automatically to suit the ambient conditions. In particularly bright or particularly dark environments, however, it can be helpful to manually set a level that you find comfortable via the options in the menu. In glaring sunshine, it is usually easier to use the viewfinder rather than the rear screen – even if you can make out the image on the LCD screen, it might be difficult to accurately assess the focus, exposure and composition.

Otherwise, lowering the LCD display brightness, and the screen refresh rate on cameras that offer this option such as EOS R System cameras, can also help extend battery life. But if you adjust the LCD or EVF brightness, remember that this won't affect the brightness of the images you capture. It's advisable to use the histogram to be sure you can assess your images' exposure accurately.

Whether it's a DSLR with an optical viewfinder or a mirrorless camera with an electronic viewfinder, all EOS cameras feature a built-in dioptric adjustment system that makes it possible to configure the viewfinder for your own eyesight. Ideally, it should be the first adjustment you make when setting up a new camera. The process is essential to ensure that both the information and the image displayed in the viewfinder are in perfect focus for you. If the dioptre setting is wrong and you are focusing manually, the image is unlikely to turn out to be sharp. If you use autofocus, the camera will probably get the subject sharp but it will look out of focus to you in the viewfinder, and of course the information display will be unclear.

The small dioptric adjustment dial is easily overlooked. It will be located close to the viewfinder, but its position varies between camera models – it may be below the eyepiece or to one side of it.

On EOS-1D and EOS 5D series DSLRs, you need to remove the rubberised eyecup to access the adjustment dial. This is best done by squeezing both sides of the eyecup together firmly between finger and thumb and then pulling carefully upwards. The eyecup is held in place by two small latches. If it does not come free easily, it may need a little more pressure, lower down, on either side of the eyecup, before pulling upwards. Sometimes pushing upwards on the base of the eyecup with an index finger may help to bring it away from the viewfinder.

Take a close look at the dioptric adjustment dial and you'll find that it has a centre point marker, which aligns with a line on the camera body. At this point, the adjustment is set to the default -1 dioptres. Above and below are plus and minus indicators, and the adjustment range is typically from about +1 to -3 dioptres.

Canon recommends that dioptric adjustments are made using your normal spectacles. However, if you prefer to use your camera without them, the process is the same.

Remove the camera lens and point the camera at a bright but diffused light source such as a window on an overcast day. Removing the lens ensures that you can concentrate on getting the viewfinder display in perfect focus.

With a mirrorless camera you will see the usual EVF information display, while with a DSLR you will see the viewfinder display and the focus screen, the surface where the camera mirror projects the image that you are capturing.

Move the dioptric adjustment dial backwards and forwards until the information display (and markings on the screen in the case of a DSLR) appear sharpest. The eye has an impressive ability to compensate for subjects that are not quite in perfect focus, so it may be worth repeating the process a couple of times to ensure that results are consistent.

Once you have finished making the dioptric adjustment, replace the lens (and eyecup if relevant) and check that when the camera autofocuses, the image in the viewfinder appears clear and crisp.