Optical & Electronic Viewfinders | Everything You Need To Know

Optical & Electronic Viewfinders | Everything You Need To Know

Options man, options. We got so many of them these days. We are absolutely and truly spoilt for choice. With the advent of the mirrorless cameras, now we have a rather “new” one, the Electronic Viewfinder (EVF). If you know what they are and how they differ from the more traditional Optical Viewfinders (OVF) found in DSLRs, then you probably don’t need to read this.

For the rest of you though, you should.

Because the only way you can make an informed choice the next time you are trying to buy a new camera is by understanding the differences and the nuances of these new technologies. And how they might add to your existing abilities or style. Everything is not for everyone.

So let’s get cracking then. This is going to be a short-n-sweet post!

The Basics

A viewfinder is generally referred to as a small hole or opening on the top half of the camera that allows the photographer to visualize the resulting image before he takes it.  

Historically many different cameras have done exactly this in many different ways. For example, Rangefinders have had separate lenses which try and mimic the view of the other lens attached in front of the sensor. Twin lens cameras also used two independent lenses but in a different way. For you to look through the camera viewfinder in a TLR camera, you needed to look down through it instead of just bringing it up to your eye. DSLRs have Optical Viewfinders which project an unaltered image straight out of the lens. And finally, mirrorless cameras use an electronic screen as a viewfinder. More on this in just a bit.

The one thing that all viewfinders should do and do well is accurately represent the image the photographer would end up recording before he takes it. The better the representation is, the better is the viewfinder. But that is not all. It also has to perform in many different situations, like low light, harsh climatic conditions, shooting fast subjects, using slow shutter speed, under bright lights, etc.

Keeping in mind these attributes of a typical camera viewfinder, let me just give you a rundown about specifically the Optical and Electronic counterparts.

Structure and Mechanism

  • OVF: Optical viewfinders have a simple mechanical design which is solely powered by light. There is literally nothing fancy about it. It just consists of a mirror and a prism mechanism which directs the incoming light from the lens up into the viewfinder.
    Diagrammatic description of how light travels inside the lens and the camera to reach the viewfinder
  • EVF: Electronic viewfinders are basically tiny screens. Think of them like your cell phone screen, just a lot smaller. When you use the camera on your phone to take an image, the whole screen shows you what the camera “sees”. This is exactly what the EVF does too. As the design goes, there are no mirrors or prism. The incoming light, in this case, falls directly on the camera sensor itself. The sensor then just projects this image on to the tiny screen which is the EVF.

Overlays

  • OVF: Since they are so simple by design, OVFs do not have a lot to offer when it comes to overlays. Most DSLR cameras show basic camera settings, such as camera mode, aperture value, shutter speed, ISO, autofocus points, light meter, a few grids, etc.

    Sharp Looking Symbology. Camera Diopter Configured Properly
    Sharp Looking Symbology
  • EVF: EVFs have a myriad of things that it can overlay on the display. Since it is all but a screen, there literally are NO limits to anything that you can put up on it. In addition to all the things a typical OVF offers, it has Live histograms, zebras, sound input levels, horizon level…..Basically, anything you want; if the camera has it, you can project it on to the EVF.

Resolution and Dynamic Range

  • OVF: There are no caps on this; includes all the resolution and dynamic range the human eye can see and perceive.
  • EVF: Most EVFs today top off at a few megapixels in resolution. Sure they have OLED displays in some high-end cameras but since they need to be placed millimeters away from the eye, the resolutions needed to match the OVF are very high. Something that they simply don’t have, as of now. It falls short of the dynamic range too. Especially when the scene has very bright and dark areas at the same time, the EVF has a really hard time reproducing it.To understand this, just walk up to your television and look really close. You will be able to find some imperfection or even individual pixels. The reason this isn’t a big deal on your TV is because you will always view it from a distance. The distance is what makes these teeny tiny imperfections go away. But when viewed from millimeters away, there is no place to hide. This is what is happening to the EVF today. However, I am pretty sure, in some years with better technologies and displays, there will be a solution to this.

Lag

  • OVF: Since it is optical in nature and projects the light as it comes in through the lens, there are NO lags at all. It shows everything literally at the speed of light (the fastest thing in the universe). It is no wonder hence that most photographers who shoot fast subjects like wildlife or sports tend to use a camera with an OVF. In an environment like that, a micro split second is the difference between a fantastic image and a worthless photograph.
  • EVF: In most mirrorless cameras though there are lags or delays. It takes time for the sensor to gather the light and then transmit it to the display on the viewfinder to project it. As compared to the yesteryears, EVFs today have extremely small lags or delays (in fraction of seconds) but it is yet to be perfected. The refresh rate has improved drastically and will only go up in the future.Your phone (which also has a mirrorless camera) has some lags too. Just hold your phone at an arm’s distance and sway it from side to side. You will see that the screen is a little late in reporting the image it is looking at. This is what we call lag.

Frame Rates

  • OVF: Owing to the mechanical parts which need to physically move to take an image, OVF installed cameras have a lower frame per second rate than mirrorless counterparts. This means when on burst mode, the camera takes comparatively less number of images per second than a similar mirrorless camera. Canon’s flagship DSLR, the Canon 1DX Mk II shoots 16 images/second and the Nikon D5 takes 12 images respectively.
  • EVF: Mirrorless cameras which use EVFs for their viewfinder all have fantastic frames per second numbers. This is mainly because they have no moving parts in between and the electronic shutter they use is mighty fast. The Sony A9 shoots at 20 fps. That is seriously fast. To put things in perspective, a standard video is shot it 24fps.

Battery Life

  • OVF: They do not need any battery to function. It is exactly like looking through a binocular or a telescope. The lens gathers the light and puts it out through the viewfinder. NO batteries are involved. Irrespective of whether the camera is on or off, the OVF always functions. This is a very important reason why DSLRs tend to have a much better battery life as compared to mirrorless cameras which need constant battery power to function.
  • EVF: Like all other screens, EVF needs a consistent rate of electric charge.  Moreover, since the incoming light is directly projected on the sensor first, it also needs to be switched on to be able to collect the light and convert them into electrical signals and send them to the EVF. Hence the camera, overall, requires a much higher battery power per unit time to function. When you switch on a mirrorless camera, virtually all of it is alive and switched on at all times. That is a heavy drain on the battery.

Visibility

  • OVF: Looking through an OVF is similar to just looking through your eyes. If you can see your subjects well with your naked eyes, you will be very able to find them through the viewfinder as well. Low-light situations are where the OVF really trumps the EVF. In harsh sunlight too, if you bring up the camera to your eye and look through it, the outside light is well cut off making the images look sharp, crisp and bright.
  • EVF: In normal day-to-day shooting, the EVF performs just fine. It provides a very accurate representation of the scene it is looking at and really helps the photographer “see”. In low-light conditions, however, there are a few problems. Since the EVF only projects how the sensor of the camera “sees” the scene to be, in low-light conditions it sometimes becomes so dark that hardly anything is visible through it anymore. On the other hand, outdoor in direct sunlight, sometimes the EVF seems a little dim and needs to be brightened up electronically to help the photographer see better. This goes against the “true representation” code but nevertheless (explanation in the image representation section below).

Camera Size

  • OVF: The design of an OVF is such that it requires mirrors and prism to be housed within the camera body to be able to function. Although it was indeed a killer reduction in weight and size from the earlier Twin Lens Cameras, by modern standards cameras with a traditional OVF do seem a little bulky. This is because by design the cameras could only be so thin. The mirror needs space to flip up and down and the prism also needs to be of a certain size to do what it does. Beyond a certain dimension, the cameras cannot go any smaller or lighter.
  • EVF: Cameras with a modern EVF do not have any such limits at all. Since it requires no such parts as the OVF, a camera with an EVF could be made much much smaller and lighter. And that is what their biggest advantages are, size and weight. Just look at the camera on your cell phone. It practically runs on the same principle as a mirrorless camera.

Image Representation

  • OVF: Although the scene representation is extremely good. Meaning that the viewfinder very accurately portrays the scene the camera is looking at (example: low-light conditions). The image representation, so as to how it would finally look once the image is recorded by the sensor is virtually non-existent. The viewfinder only shows what the scene actually looks like, the settings of the camera notwithstanding. This means that no matter what settings you use to take an image, the viewfinder ALWAYS shows you the same representation.Certain important aspects of photography like exposure and depth of field are absolutely disregarded here. The image shown on the OVF does not reflect at all the amount of depth of field an image would have or if the exposure is correct or not. You have to read the light meter and adjust the settings for the same.
  • EVF: This follows a ‘What You See Is What You Get’ (WYSIWYG) policy. Looking through the EVF is essentially looking at the scene through the image sensor’s eyes. Whatever changes you make to the camera settings makes a difference to how the sensor sees it. This is immediately reflected on the EVF as well (*conditions apply). So in effect, you can see the amount of depth of field the final image would have and also have a pretty good idea about the exposure just by looking at the EVF.

    *Conditions: Very long exposures are NOT represented on the EVF at all. If you set a shutter speed of more than a second in most cases, the EVF just shows you the image without taking into account the effect of such a long shutter speed at all. Basically, it would not be able to show you the amount of potential blur or streaks the final image would have if you exposed for that long.

Blackout

  • OVF: By design, the mirror placed at 45 degrees in front of the image sensor needs to be flipped up so that the light can reach the sensor behind it to record the image. In an OVF mechanism, it is an “either or” situation. Light incoming through the lens is either received by the viewfinder OR the sensor. Both of them cannot have the light at the same time.

    By virtue of this design, OVF does have blackouts (the period for which the mirror is flipped up and no light reaches the viewfinder). The longer the shutter speed, longer the mirror needs to stay up and longer the blackout. If you take a 30 seconds exposure, the blackout will also be 30 seconds long. You will see nothing but darkness during this period.

  • EVF: Most cameras with an EVF do NOT have any blackouts at all. The sensor is always on and the viewfinder continuously reproduces the scene as it changes. In fact, to make up for the lack of blackouts which was a definitive sign of an image recording, modern mirrorless cameras had to come up with new ways of reporting an image record. Some cameras have a white border along the viewfinder everytime an image was recorded. Others had a green dot or something similar.

Video Shooting and Playback

  • OVF: To record video, the image sensor needs to receive continuous light for the duration of the recording. For the reasons stated above, to record video, the OVF needs to be switched off completely. It is absolutely impossible to shoot a video using an OVF.
  • EVF: Shooting a video using an EVF is a breeze. You can hold the camera up to your eyes and just keep filming just like you take images. Holding the camera so close to your body will help negate jerks and will be a lot more stabilized. You can also use the EVF to change settings on the fly. Once done, it can also be used to playback the recording. Pretty nifty huh! It’s a screen after all, that is what it does.

Which One Is “Better”

Like I said, in the beginning, it all depends. Depending on your style of shooting and the subjects you shoot, you might like one or the other. The OVF has been in the industry for many decades now and for good reason. It is one of the most accurate and precise representations of the scene. It is fast and versatile too. Sure it has some limitations but having used it for a sufficient amount of time, I can assure you there are very easy solutions too.

The problem of blackouts

Let’s say that you are shooting an extremely long exposure, say 5 minutes. Whether or not you can see through the camera for that duration doesn’t matter at all. You would have to in all probability, fix your camera on a tripod and keep it STILL for that duration. How will showing you the scene through the viewfinder help anyways?

When shooting extremely fast subjects like sports, the shutter speeds used are much faster too. Hence the period of blackouts is also much shorter. You might have an extended blackout if you shoot many frames at once but my reasoning is if you need so many shots to get a proper image you might as well shoot video. Its just ‘spray and pray’ approach.

The EVF has come a long way since it was first introduced. It has grown in resolution, dynamic range, refresh rates, efficiency and is going to just go up from here. In due time, it would probably find alternative solutions to the problems it has over OVFs. I do dig into the WYSIWYG policy of electronic viewfinders and I do think they help lot in certain situations.

Now it is for you to decide which are the functions that you would need to shoot? Remember, that your answer will also dictate whether you choose a mirrorless or a traditional DSLR. You cannot have a camera type with a viewfinder supported by the other one.

Keep shooting amazing.

This is now a teeny tiny blog trying to compete with the big guys. If you liked what you read, it would mean a lot to me if you could take a second to share it. Thank you.

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