With no mirror or optical viewfinder, MILCs utilize data coming off of the imaging sensor to display the TTL (Through the Lens) view on an LCD. That LCD panel can be on the back of the camera or in a viewfinder where it is typically referred to as an EVF (Electronic Viewfinder). This is not a new technology, but one that has been utilized by many non-MILC digital cameras, practically since digital cameras existed.
Relevant to this site’s audience is the replacement of the traditional DSLR OVF with an EVF. Safe to say is that all high-grade cameras produced today have an LCD that can be used for mirror-up, live view of an image that is about to be captured. Therefore, the benefits of an EVF (Electronic Viewfinder) relate to being able to see an LCD with the camera placed at one’s eye. Making the difference less black and white is that LCD viewfinders/shades/loupes, such as those by Hoodman, are available for use on the rear LCD, effectively giving all digital cameras an “EVF”.
To get started with the comparisons, let’s look at:
The Advantages of All Live View LCD Displays Over Optical Viewfinders
A big advantage of an electronic viewfinder is the WYSIWYG (What You See is What You Get) image preview. Able to be included in the LCD image preview is the actual exposure brightness, optionally including a histogram and over/underexposure warnings. Also able to be included in the preview are the net results of other camera settings being applied, including white balance, contrast and saturation. This preview is usually able to show a 100% view of the composition vs. a slightly cropped view shown by many OVFs.
When shooting in a very dark environment, it becomes very difficult to compose an image using an optical viewfinder. By using an amplified signal from the sensor, an LCD viewfinder can present a much brighter image that greatly facilitates composition. A “dark environment” can include the use of a strong neutral density filter under even bright daylight conditions.
Under the extreme opposite lighting conditions, the LCD can offer protection to your eyes. At the extreme end of the brightness category, the sun poses a serious risk to eyesight. Eye damage can easily occur if looking at the sun through an OVF, especially with a telephoto focal length in use. An LCD’s maximum brightness is not dangerous to the eye, even with the sun in the center of the frame. There is little risk to your eyes when viewing the sun in an LCD, but note that your camera may not fare as well.
An LCD does not need a viewfinder shutter or cover to prevent unwanted light from affecting the metering or exposure.
A mirror assembly is required for OVFs, but not for LCDs. Removing the mirror assembly has some advantages, including the cost of the assembly being eliminated (though EVFs also have a cost that must be factored back in). The mirror assembly has moving parts and moving parts may eventually require replacement (though the life of a DSLR mirror assembly is usually a very significant number of actuations).
The lack of mirror movement creates some additional benefits. First, a mirror rapidly flipping up and down makes noise and a camera operating without a mirror is considerably quieter. Mirror movement causing vibration during the exposure becomes a non-concern. Also, the mirror lockup function becomes obsolete. Without the rapid mirror movement, airflow in the mirror box is reduced, which may in turn reduce instances of dust adhering on the sensor. Take the lens off of an electronic first curtain shutter MILC (a common design) and the imaging sensor is right there, easily accessible for cleaning.
The lack of a mirror forces another primary differentiator between non-OVF vs. OVF cameras and that is, without a mirror, the imaging sensor must be used for all pre-shot calculations, including auto focus and auto exposure. While there are some disadvantages to the mirrorless design in these regards (primarily related to AF speed), those weaknesses are diminishing as technology moves forward. One advantage is that the LCD provides a much larger AF area coverage with (at least potentially) more AF points. Another is that, with focusing taking place precisely on the imaging sensor, AFMA (Auto Focus Microadjustment) is no longer needed and lens focus calibration becomes a non-issue.
With the LCD previewing the image about to be captured, precise focusing can be monitored, including focus peaking indication. Also, an enlarged view of a portion of the frame can be selected to verify focusing or to aid in precise manual focusing. With the tremendously detailed information the sensor makes available, technologies including face and smile detection can be implemented.
While intelligent optical viewfinders have shown great advances in recent years, complete with transparent LCD overlays, they don’t come close to the capabilities of LCDs in terms of the information that can be shown. A high-resolution LCD panel with a huge palette of colors available provides designers great flexibility in creating a camera’s graphical user interface and also in the customization capability of that interface.
Though a bigger advantage for true EVF cameras, LCD displays can provide an immediate display of a captured image precisely where the photographer is looking at time the image is captured (such as directly through the viewfinder). However, I must note that this review interrupts the capture of a subsequent image and that I now turn off the image review feature on the EVF cameras I’m using. Still, the press of a button brings the image review display up without the need to move the camera or look elsewhere.
While some manufacturers (including Canon and Nikon) contend that image stabilization technology works best in the lens vs. in-camera (and there is validity to this claim), inarguable is that the effects of in-camera image stabilization will not be seen in an optical viewfinder, leaving the view shaky.
Again, camera-back LCDs and EVFs (which also use an LCD) share the benefits just described.
Differences Between Primary LCDs and Viewfinders (Both EVFs and OVFs)
As mentioned, when it gets dark, LCD live view displays and EVFs are much easier to compose with than OVFs. However, in bright daylight, even the best rear LCDs become very difficult to see and I find it especially challenging to compose using the rear LCD under direct sunlight. In contrast, viewfinders make it easy to critically view the composition under even the brightest conditions, giving them a huge advantage over a rear LCD under bright daylight conditions.
I wear eyeglasses a good percentage of the time (and that percentage is increasing). If you do not need corrective optics now, you will – it is only a matter of time. I have reading/computer glasses and another set with a distance prescription for seeing longer distances. When out and about with a camera, I seldom have both sets of glasses with me and I often wear none. This means that the image on the camera’s rear LCD, within arm’s length, appears slightly fuzzy to me. Yes, bifocals and trifocals are options that would help with this issue, but … I have not appreciated the limited views that these provide. Dioptric adjustments provided by viewfinders resolve this issue, permitting a clear view of what I’m about to photograph and review of what I already photographed.
Another key viewfinder advantage is that it provides additional stability for holding the camera steady. While it can also lead to AEB, the camera pressed against an eyebrow adds a significant third point of stability in addition to two hands. Also, this position allows both elbows to be tucked into the ribs, increasing stability even more.
A camera’s primary LCD tends to collect fingerprints and other smudges at a rapid pace and these can interfere with visibility of the display, especially in bright light. A viewfinder, to the contrary, tends to stay clean. However, a viewfinder, with its inset glass, is harder to clean than a primary LCD that, especially if properly coated, easily wipes clean with a microfiber cloth.
Advantages of Electronic Viewfinders over Main LCDs
As mentioned, an accessory viewfinder/shade/loupe can turn a camera’s rear LCD into the equivalent of an EVF. A downside is that LCD loupes are not nearly as well integrated into the camera design as EVFs are – built-in EVFs are considerably more compact and less intrusive. External loupes also get in the way of touch screen functionality.
Advantages of Eliminating the OVF
A primary attraction of MILCs is their smaller size and lighter weight. Eliminating the mirror box and OVF immediately reduce the footprint of a camera, permitting these design advantages.
Advantages of Optical Viewfinders
With resolution not limited by dots of pixels (that can appear to flicker as they change colors when framing is adjusted) and refresh rates not limited by an electronic display, huge advantages of an OVF include resolution and responsiveness. In addition to seemingly unlimited resolution and refresh rates happening at the speed of light, OVF dynamic range is limited only by our eyesight. An LCD has a limited dynamic range and may show blocked shadows and blown highlights. Though the dynamic range of the image captured via an OVF system will similarly be limited by the imaging sensor, seeing the full brightness range is different.
The EVF properties just discussed can leave the photographer feeling somewhat disconnected from the moment, akin to watching a movie of an event vs. seeing it in-person as an OVF provides the sense of.
While an LCD can make low light composition easier, a photographer’s eye must constantly adjust between the bright display and dark ambient light levels. Generally speaking, the brightness seen through an OVF is similar to what is seen without the camera in use.
While removing the mirror assembly brings some advantages, the mirror provides a level of protection to the imaging sensor. Take the lens off of an OVF camera and it is the mirror that becomes exposed instead of the imaging sensor.
While not directly related to the viewfinder type, MILCs are very commonly given EVFs with reduced camera size and weight being two of the common design targets. Especially with the smaller MILCs, using large lenses and full-sized flashes can lead to a tail-wagging-the-dog scenario where the provided grip is inadequate or only marginally adequate to maintain control of the overall setup. OVF cameras are often larger, making larger lenses and flashes easier to control.
While on the size topic, If considering an MILC for size and weight reduction purposes, make sure that the MILC lenses you need do not make up for some of the camera footprint and weight difference. While most of these cameras indeed have a smaller footprint than their DSLR equivalents, the size of the lenses needs to be considered and these are not necessarily smaller. The smaller camera does not change optical properties and the image circle size required by the same-size sensor remains the same.
Though these cameras often utilize a short back-focus lens design and some lenses are indeed smaller, some of the smaller lenses also have narrower maximum apertures. MILCs may need an adapter to use the manufacturer’s standard lenses (the Canon EOS M series for example). While an adaptor can tremendously extend the number of lenses a camera is compatible with, it is an extra part to buy, carry and use. And, it makes the camera (or each lens) effectively larger and heavier in use, with the EF to EOS-M adaptor adding a modest 1″ (26mm) and 3.77 oz. (107g) respectively.
With the imaging sensor required to be powered up for an EVF to function and because an EVF’s full-color LCD requires its own share of power, EVFs require more battery capacity for an equivalent number of photos to be captured. However, battery size, and with it, capacity is a typical sacrifice made by MILCs. As a result, cameras with EVFs often have considerably lower battery life ratings. A faster battery exhaustion rate greatly increases the chance that the battery will become fully drained just when the perfect image presents itself (one of Bryan’s Laws of Photography).
Roughly figure an EVF system to require at least twice as many batteries as an OVF system. If you often carry a spare battery with your OVF camera, you should probably carry 3 or 4 with an EVF camera. Additional batteries add to the system cost, carrying extra batteries adds to the system weight and maintaining the charge of additional batteries requires maintenance and logistics – and probably at least a second charger as you can potentially drain batteries faster than you can charge them.
Do you ever look through your viewfinder with the camera powered off? Perhaps when setting up a tripod and composing a scene? Complete blackness is what you will see if doing so with an EVF camera.
If shooting action, I still want an OVF. While EVFs have made great strides in recent years, they have not yet equaled OVF systems in some important regards, especially in their ability to capturing a precise moment of action. As mentioned, EVF response rates are not light-speed and every microsecond counts when a precise moment in time needs to be captured. Advances in on-sensor AF capabilities have brought recently-produced EVF camera performance much closer to the traditional phase detection systems found in OVF cameras. But, traditional phase-detection AF systems still modestly outperform current on-sensor performance in the critical-for-action speed component.
Most OVF systems have a significantly shorter blackout time during the image capture and if following action, this is a critical factor. The difference at this time (Canon EOS M5 and Sony a7R II era) is significant enough that I find EVF cameras practically unusable for tracking/framing a moving subject even with image review turned off. I can keep a straight-on-approaching/leaving subject in the frame for a period of time with an EVF, but if they move to the side, my framing quickly falls apart.
So, back to the questions: Is an electronic viewfinder (EVF) better than an optical viewfinder (OVF) and is an EVF an acceptable alternative to an OVF?
The answer to both of those questions is yes or no. It depends. Both designs have advantages and disadvantages and how appropriate either type is for you depends on your personal needs.
As mentioned, using a shade/loupe/viewfinder on the rear LCD can provide the EVF features to most cameras and cameras with an OVF can then have the best of both features. Better still is the talk of a hybrid viewfinder being introduced. Such would feature the option of an OVF or an EVF selectable as desired. Transparent LCD overlays have been available in better DSLR models for years now, so the idea does not seem far-fetched.