Mirrorless vs DSLR – Everything You Need To Know

Last Updated on July 12, 2015 by PixelPluck

Mirrorless vs DSLR – Everything You Need To Know.

While we’ve all been discussing the death of the point-and-shoot at the hand of the smartphones, mirrorless cameras have gradually been making their way into the professional category by boosting quality, performance and features. But how far have they really come? Can a professional photographer really scrap DSLRs and go mirrorless?

Mirrorless cameras existed back in the analog days in a rangefinder design made famous by the legendary Leica brand. Digital mirrorless models emerged in 2008 when Panasonic and Olympus formed an alliance around a new Micro Four Thirds sensor format that allowed for near-DSLR image quality but allowed for much smaller camera bodies and lenses.

SLR vs Mirrorless Construction
SLR vs Mirrorless Construction

Modern DSLR cameras by design have some inherent flaws and limitations in them. This may be due to the fact that SLR cameras were initially developed for film. When digital evolved, it was treated just like film and was housed in the same mechanical body. Aside from the circuitry required for a digital sensor and other electronics, new digital film media and the back LCD, the rest of the SLR components did not change. Same mechanical mirror, same pentaprism / optical viewfinder, same phase detection system for autofocus operation. Their savings in bulk and weight are possible because these cameras get rid of the optical viewfinders found in DSLRs (higher-end models replace them with electronic ones) eliminating the need for a flip-up mirror as well as the viewfinder housing that gives DSLRs their distinctive hump above the lens mount.

While new technological advances eventually led to extending of features of these cameras (In-camera editing, HDR, GPS, WiFi, etc), DSLRs continued to stay bulky for a couple of reasons. First, the mirror inside DSLR cameras had to be the same in size as the digital sensor, taking up plenty of space. Second, the pentaprism that converts vertical rays to horizontal in the viewfinder also had to match the size of the mirror, making the top portion of DSLRs bulky.

DSLR Camera Limitations

All DSLRs are dependent on mirror for “through the lens (TTL)” viewing, so they have the following limitations:

  • Size and Bulk : Reflex system needs space for both the mirror and the prism. This leads to wider body and protruded top.
  • Weight: Large size and bulk also translates to more weight. While the entry level DSLRs have plastic body, the professional DSLRs have alloy metal body. This increases the weight significantly. Lighter alloys are expensive and adds to the cost of camera.
  • Complex Mirror and Shutter Design: Every actuation requires the mirror to move up and down to let the light pass through directly onto the sensor. This alone creates a number of issues like
    Mirror Slap: Results in loud noise and camera shake.
    Movement of Air: As the mirror flips up and down, it moves plenty of air inside the camera chamber.
    Frame Speed Limitation: Even the Nikon D4 can only do 11fps.
    Expensive to Build and Support: The mirror mechanism is very complex and consists of dozens of different parts.
  • No Live Preview: When looking through an optical viewfinder, it is impossible to see what the image is actually going to look like. You have to look at the camera meter (which can be fooled in some situations) and adjust the exposure accordingly.
  • Lens Calibration Issues : Traditional DSLR phase detection system not only lies with the secondary mirror alignment issues, but also requires lenses to be properly calibrated.
  • Cost : Mirror mechanism is complex and costs a lot. It needs regular maintenance.

So what advantage does mirrorless camera have?

  • Smaller Size / Bulk and Lighter Weight: Removing the mirror and the pentaprism frees up a lot of space.
    Camera size comparision
    Camera size comparision
  • No Mirror Mechanism:
    → Less Noise: No more mirror slap, just the click of the shutter is all you hear.
    → Less Camera Shake: Unlike the mirror in a DSLR, the shutter by itself does not produce a lot of vibrations, resulting in less camera shake.
    → No Movement of Air: Since there is nothing constantly moving inside the camera chamber, dust is less of an issue here.
    → Easier to Clean: If dust does end up on the sensor, cleaning mirrorless cameras is easier than DSLRs. You do not need a fully charged battery to lock up the mirror – the sensor is exposed once you dismount the lens. Also most mirrorless cameras do not have an opening under the mirror to house a phase detection sensor and other components, so there is very little chance for dust to circulate after the chamber + sensor are fully cleaned.
    Very Fast FPS Speed: Having no mirror means that the capture rate (fps) does not have to be limited by the mirror speed. This means that mirrorless cameras could potentially capture images at much faster frame rates than 10-12 FPS we see today, with much less noise.
    Cheaper to Build and Support: Less moving parts translate to lower cost of manufacturing and support for the manufacturer.
  • Live Preview: In case you messed up White Balance, Saturation or Contrast, you will see it in live preview – whether in the EVF (see below) or the LCD.
  • Electronic Viewfinder: Now here comes the biggest strength of mirrorless cameras and the present + future innovation with it. Without a doubt, an EVF has huge advantages over OVF. While the current implementation of EVF might not be as robust and responsive as it should be, it is just a matter of time before manufacturers fix that.

Key benefits of EVF over OVF:

  • Information Overlay: With OVF, you never get to see more than some basic grids. There is some static information presented in the viewfinder, but it is always fixed and cannot be easily changed. With EVF, you can get any information you want displayed right inside the viewfinder – from live exposure data to histograms. Different warnings could be added, such as a warning for a potentially blurry shot.
  • Live Preview: The same live preview on the LCD can be shown inside the EVF.
  • Image Review: Another key feature that you will never get in an OVF is image review. How cool would it be to see the image that you have just captured right inside the viewfinder? With OVF, you are forced to look at the LCD screen, which is a big pain in daylight conditions. People buy a Hoodman Loupe to be able to see their LCD screen in daylight on their DSLR! With EVF, you never have to worry about this, since you could use the viewfinder for reviewing images instead.
  • No More Viewfinder Coverage: With OVF, what you see in the viewfinder is about 1-5 % smaller than what the camera will capture. EVF will always be 100% viewfinder coverage, since what you see in the EVF is what the sensor will capture.
  • Brighter Display: When light conditions are poor, you cannot really tell if the subject is in focus until you take the picture. With EVF, brightness levels can be “normalized”, so that you can see everything as if it was daylight. Some noise might be present, but it is still way better.
  • Digital Zoom: Very useful and popular feature! If you have used a Live View mode on your DSLR before, you know how helpful zooming in can be. With most modern DSLRs, you can zoom in to 100% and really nail focus. Well, with mirrorless cameras, this feature can be built right into the viewfinder! So imagine manually focusing with a lens, then zooming in to 100% right inside the viewfinder before you take the picture. A number of mirrorless cameras are already capable of doing this. It goes without saying that an OVF would never be able to zoom like that.
  • Face / Eye Tracking: This is the coolest part of the EVF technology. Because the EVF shows what actually happens on the sensor, additional technologies for data analysis can be utilized to do very cool things, like face and even eye tracking! You can take it a step further and could have the camera automatically focus on the nearest eye of the person that you are photographing. How cool is that? Sony is already doing this on their new Sony A7/A7R cameras!
  • Potentially unlimited focus points: DSLR cameras have a limited number of focus points that are distributed mostly around the center of the frame. While it works out in most situations, what do you do if you need to move the focus point to an extreme border of the frame? The only option is to focus and recompose, but that might not be always desirable, since you are also shifting the plane of focus. In addition, anything away from the center focus point is typically inaccurate and could result in “focus hunting”, where the camera struggles with AF acquisition and goes back and forth continuously. With mirrorless cameras and phase detection sensors placed directly on the imaging sensor, this limitation can be lifted. Contrast-detection is already possible anywhere in the imaging sensor, while on-sensor phase detection will eventually get to the point where focus points will be distributed all over the sensor.
  • Subject Tracking and other Future Data Analysis: Face tracking opens up a whole new innovation opportunity. Imaging having a complex tracking system that intelligently combines sensor data with autofocus and uses it to track a given object, or subject in the frame. Even the top of the line DSLR cameras today have challenges with full subject tracking. If you have tried photographing birds in flight with a DSLR, tracking can get challenging, especially when the bird moves out of the focus point area, or when the light conditions are less than ideal. If data is analyzed on a pixel level and there is no real autofocus area to concentrate on, subject tracking could potentially get super advanced with mirrorless cameras.
  • Eye damage: when looking through a viewfinder, one has to be extremely careful about photographing the sun, especially with long focal length lenses. With EVF, the image is projected through the sensor and there is no harm to your eyes.

Mirrorless Camera Limitations

  • EVF Lag: While some of the models are fast, some are relatively slow.
  • Continuous Autofocus / Subject Tracking: This is where DSLRs have the upper hand.
  • Battery Life : Only around 300 shots. DSLRs give more than double of that.
  • You Might Not Look as Cool : This one is totally superficial, but many photographers secretly think of it right away. Walk into a wedding/event with Canon 5D Mark III  / Nikon D4s with a 70-200mm lens on the front and people will trust you more. Good or Bad but that’s the way it is.

DSLRs simply have no way to compete with mirrorless in the future. But we are still far from that point when everyone will be switching to smaller and lighter mirrorless cameras.
What do you think? When are you going to switch? Which model will you prefer? Share with us in comments below.

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One comment

  1. Wow! Not even 1 piece of Panasonic camera to compare, the maker of the very first mirrorless camera, the G1. And the author maybe never ever heared about GH4 as well. Nice!
    (Not speaking about Fuji…)

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