Mirrorless Gains and Losses

I overcame size with mechanics (Edwin Moses)

Almost the first thing that someone new to mirrorless cameras asks is this: how good are they? 

Well, they're quite good, as long as you don't buy one that's pink ;~). 

As with many things in life, you gain something and lose something when you pick a smaller or larger product. In the case of interchangeable lens cameras, that can get a little murkier than usual, as they're quite a range of product in this category. But a few things are clearly evident.

Mirrorless Losses
First, we have the obvious: you lose the mirrorbox when you move from a DSLR to a mirrorless camera. With that change comes the loss of an optical viewing system (it will be replaced with electronic screens, which are not the same thing as a clear optical view). In some lower priced or older mirrorless cameras, you may also lose phase detect autofocus. That last bit is important because phase detect autofocus generally has faster subject acquisition (at a minor expense of accuracy) and far better focus tracking capabilities than an all contrast-based system. 

The loss of the mirrorbox also means that you lose some bulk. The mirror inside DSLR cameras pushes the lens mount forward from the sensor (the swinging mirror needs clearance). In a typical cropped sensor DSLR (APS, DX), that probably adds an inch to the depth of the camera, though there's a great deal of variation between models, so it's impossible to come up with an exact number. Still, a mirrorless camera, all else equal, will typically always be thinner than a DSLR. It also may be less tall if it doesn't have an electronic viewfinder (EVF) to replace the optical one in the DSLR.

The mirrorless diet tends to produce cameras that are lighter and less bulky, all else equal. Some mirrorless cameras get very close to compact camera size, yet retain higher capabilities.

No mirror potentially means less vibration that might impact slow shutter speeds and promote a slight camera motion to pixels in some conditions. Unfortunately, the shutter itself can impart visible shake at some shutter speeds (early m4/3 cameras were notorious for this).

But there are losses that might not be so great, too.

Most mirrorless cameras leave the sensor exposed (shutter is left open when not taking a picture, and there's no mirror in front to quasi-protect the sensor, either). Coupled with the fact it is so close to the mount, that makes it easy to get water, dirt, or something else on them, or to even damage them if you aren't mindful of their vulnerability. 

You're not looking at reality with a mirrorless camera (either via the rear LCD or a built-in EVF): you're looking at a slightly delayed interpretation of reality that’s close to what the camera would capture (i.e. exposure, contrast, saturation information can be seen). It takes a bit of time to grab an image from the sensor, shuffle it through the camera's electronics, and display it on the electronic displays. On some cameras this "lag" is extremely slight (Fujifilm X-H1, Sony A9, for instance), while on others it's significant (Fujifilm X-A5, Sony A6000, for example). In any case, you've lost seeing things exactly in real time as you're composing. (Most people adjust to this with practice, even on the cameras with the most lag, but it makes it more difficult to capture peak action without using continuous bursts.)

With some cameras, mostly low end, we also lose some sophistication. The camera makers seem to think most mirrorless cameras are likely to be bought by more entry-level users, and thus while they often have some DSLR-like control in them, this is usually watered down in control capability, flexibility, feature depth, or all of the above. That said, the high-end mirrorless cameras—the GH5, E-M1II, X-T2/X-H1, and A7/A9 come to mind—are pretty much the equivalent of high-level DSLRs though.

The smaller size of most mirrorless cameras means that buttons and controls tend to get smaller. Using many of these cameras with gloves on (winter shooting) can be a problem. I've got one mirrorless camera that has maybe a dozen small buttons on it that are problematic to find and use with anything but the thinnest gloves on. And I mean really thin gloves, as in glove liners.

It's not necessarily a loss, but if you're coming from bigger DSLRs that use CompactFlash cards, the smaller size of most mirrorless cameras means they almost all use the smaller Secure Digital (SD) cards. A few use very small microSD cards, so take a close look at how images are stored if you’re making a transition.

One potentially big loss is battery oomph. The smaller sizes of most mirrorless cameras means that they often pack smaller batteries, as well. Given that the LCD and/or EVF is always on with these cameras, you'll get significantly fewer images per charge than you do with even the low-end DSLRs (unless you always shoot with your DSLR in Live View). 

Many of the mirrorless cameras have other losses, as well: watch out for weak or non-existent flashes, missing remote controls, missing GPS support, missing hand grips, and a host of other things. While these are called "system cameras" by the makers, the system isn't always fully accessorized.

Mirrorless Gains
I've probably gotten you pretty depressed with all the losses I describe, so the gains better make up for it, right?

Autofocus on most mirrorless cameras is now competitive with low-end DSLRs, at least for initial subject acquisition. But the good news is that, because they use contrast-based autofocus—even the phase detect-based mirrorless cameras tend to do this as a last step when in single servo autofocus—they tend to be better at things like face recognition. When these cameras say they're in focus, they're in focus.  

The reduced size means reduced carrying issues. In some cases, that can be considerably reduced from even the low-end DSLRs. Several of the mirrorless cameras are what I'd call jacket-pocketable, even with their kit zoom lens mounted. There's a big difference between two to five pounds of weight hanging from your neck all day and a pound of stuff in your pocket. A big difference that can get bigger when we get to lenses (more in a bit). 

But be careful. Some of the size advantage of mirrorless is that they use smaller sensors. That’s particularly true of m4/3. Once we get to full frame mirrorless (e.g. the Sony A7/A9 series), lenses tend to be the same size as equivalent DSLR lenses, and the size/weight advantage begins to disappear.

Likewise, the weight limits some airlines are now imposing on carry-ons come into play. On assignment with my DX DSLR gear I'm typically in the 20-30 pound pack range. With FX gear, I'm almost always over 30 pounds. And that's for a minimal kit. My usual m4/3 kit not only weighs less than 10 pounds, but it fits in my laptop bag. Yes, in my laptop bag. That's two camera bodies, three lenses that take me from 14mm to 300mm equivalent, a bunch of accessories, and my laptop. (Some of you are asking "which laptop bag is that?" The Tenba Messanger Small bag. It'll hold a 15" laptop and all that mirrorless gear I just mentioned, and still have some room left over. Use the link, below to order one and support this site.)


With the smaller size tends to come smaller lenses. Not always, as I noted above, but with many models there can be significant savings in size in lenses, too. First, because the mirror box is missing, the wide angle and normal lenses are designed for a short back focus and can be smaller. While the mount-to-sensor distance alone doesn't dictate small lenses, it has put a different twist on what consititutes the right sized lens, particularly for the wider angle lenses. Different companies have gone at this differently.

Olympus, for example, has put a strong emphasis on small lenses. Coupled with their 2x crop sensor, which already has a small image circle, Olympus has thought to make many of their lenses “collapsing”—they're smaller when not being used than when they are. The 9-18mm and the 14-42mm kit lens are two good examples of lenses that are extremely small while traveling, yet still quite competent in use.

Sony is at the other extreme. It appears that they originally pretty much took their APS designs and did little tweaking to make them smaller. Other than the 16mm f/2.8 lens, almost none of Sony's E-Mount lenses can be considered small for the sensor size, though many of them are fairly light in weight. The FE-Mount for the Sony A7 cameras is more of the same, in spades, particularly when you get to the f/2.8 zooms.

So the size/weight/traveling benefits vary between the different mirrorless options. Right now you can pick between the small 1” sensor Nikon J5 and the much larger full frame Sony FE mount cameras. So the gain here is quite variable. Make sure you know what it is you're seeking in terms of light/small and make sure that the camera you choose attains that.

Another thing that people like to point out is that, since these cameras do very respectable video—and in some cases, like the GH5, superb 4K video)—you can stuff them in places that you normally can't get a regular video camera. Olympus Pen cameras were used to film in places on the track for the movie Secretariat, for example, including in the starting gate. Thin is good when you're trying to pin a camera to a wall.

It may not seem like it at first, but there are certainly other gains, some of which you might not have thought of.

For example, when I use my mirrorless cameras, I can often shoot without looking like I'm shooting. Yes, I know that I can do something similar with Live View on many DSLRs, but the small size coupled with "not-at-eye" shooting (especially with the tilt/swivel LCDs) means people just don't pay a lot of attention to me when I'm shooting with mirrorless cameras. It makes it easier for capturing true candids, I think (obviously some cameras are better at this than others, but all the mirrorless cameras look at lot less professional and trigger less "look at me while I'm shooting you” response than my big FX DSLRs. 

But What About Image Quality?
I've been conspicuously avoiding talking about image quality for a reason: there's quite a variation here, and it also depends upon what you're trying to accomplish. 

At the extreme end of the scale, the sensor on the Pentax Q is so small it's...well, it's a sensor from a compact camera. That means that the Q tends to perform like a compact camera when it comes to image quality, which is to say that it struggles with very low light situations. 

At the other extreme, we have the Sony offerings with their state-of-the-art full frame sensors. The A7rIII model clocks in at 42mp, the A7III and A9 at 24mp, the A7s at 12mp. All shoot as well as the best full frame DSLRs in low light, plus the first one has a pixel count that lets you print extremely large.

But is that what you really need? Are you really shooting at ISO 3200 and above and are you really printing at 19" and above? Because if you aren't, some of the smaller sensor models in the mirrorless realm might work perfectly fine for you. 

Moreover, the m4/3 models offer a lot of fast lens choice, and fast lenses are just as instrumental as sensor when tackling low light. Compare the 12mm f/2 on the Olympus Pens with the 16mm f/2.8 on the Sony E-Mount. From an exposure standpoint, you're shooting a stop faster with the same angle of view, so if the Sony is at ISO 1600, the Pen is at ISO 800 with the same shutter speed. (Yes, I know there are still some other factors involved, but let's not get down in the weeds on a general introduction article. We're in the "did you get the picture and is it decent" realm here.) The Olympus is also stabilized (via the sensor), while most Sony APS-C models are not, which may mean that you can use slower shutter speeds (but not if there's subject motion).

That said, I've been shooting with m4/3 cameras for over eight years now. From the beginning, I've found them functional, useful, and capable of all the image quality I need for many types of photography. With the right lens set, I'm not particularly afraid of low light. For my landscape work, I often use stitching techniques for large prints anyway, so I end up with a smaller, simpler system that I can carry further into the backcountry. Here's an example of one such stitched image that prints nicely at over 36” wide (taken with an Olympus E-P2):

US UT Escalante 0412 EP1

During the time I’ve been shooting mirrorless, I've posted a lot of shots without referencing what camera they came from. People weren't saying "oh, that must have been from one of those small cameras you've been using" or "that must be from you high-end DSLR." In the end, cameras are just tools. You learn how to optimize your use of the tool and you go out and create. 

This is not to say there aren't limits. The m4/3 cameras, in particular, just don't cut it for me to perform really low light work. Nor are they always the right choice for me when I do wildlife work (I shoot an awful lot before dawn and after sunset, and with big lenses). But I use small mirrorless cameras for quite a bit of my shooting these days, more than most people may imagine. 

The Bottom Line
Assess your needs. Assess what these mirrorless cameras can do (I'll try to help with my reviews and other articles on this site). If the two things overlap, then welcome to the sans mirror club. If they don't, well, check out my other sites, as I have information about larger and smaller cameras there. 


text and images © 2018 Thom Hogan
portions Copyright 1999-2017 Thom Hogan-- All Rights Reserved
Follow us on Twitter: @bythom, hashtags #bythom, #sansmirror