The Differences Between DSLRs And Mirrorless Cameras

A camera — in essence — is nothing more than a sealed box with a small hole (the lens) at the front, which collects light and "beams" an image onto a light-sensitive surface inside in order to record an image. That opening line always caught people's attention when I used it during photography workshops.  

It's a very simple, bare-bones definition, and true in essence, but there is a lot more to these devices that allow us to capture and preserve moments in time so easily and effortlessly. Now we have various types of cameras, but there are two most photographers and hobbyists use today — DSLR and mirrorless.

Though there is no clear answer across the board as to which is better, this debate still rages in the photography world. So let's dive deep to take a look at what a camera actually is in terms of the method of how pictures are captured, and how these two types of camera differ in that respect. We'll also look at each one's respective pros and cons.

To talk about the similarities and differences between these two types of modern cameras, first, we need to understand the inner workings of modern cameras.

Based on the SLR, or Single Lens Reflex cameras, which came on the scene just after WWII, both DSLR and mirrorless cameras feature:

• a lens through which the light enters the body and gets focused 
• a medium to record the images — namely, the sensor
• a shutter mechanism in front of it to control the amount of light exposure on the sensor at one time
• a viewfinder through which you can compose the scene you want to capture

In a DSLR, you also have the mirror array inside. 

This is the biggest difference between these camera types. As the name suggests, mirrorless do not have a mirror, thus allowing them to be smaller, more lightweight, and more compact in general. I've been teaching photography principles for many years now and within the last three years or so, I've seen a dramatic increase in people using mirrorless cameras, hinting at a major focus shift in the industry.  

While DSLRs still use optical viewfinders, mirrorless cameras instead use power-intensive electronic viewfinders, and it's only the very best of these that are able to even approach the immediacy of their optical counterparts. For most commercially available models, a trained eye can notice a slight visual lag on the screen. It's not the end of the world, but still detracts a bit from "being in the zone" when you're taking a picture. As a photographer, I've always thought there is a sort of meditative aspect to taking pictures, and for me, at least, it was more difficult to get that same feeling looking at a screen instead of straight through the lens such as in optical viewfinders.

Progress is inevitable, however, and electronic viewfinders have come a long way from their first iterations just a few years ago. They are getting quite a lot better these days, approaching a clarity that genuinely reflects optical viewfinders in both resolution and (lack of) lag (via Digital Camera World). Panasonic's Lumix S cameras brought the highest electronic viewfinder (EVF) resolution to the table at over 5 million dots, and Sony's A1 has an astounding 9.44 million dots to offer.

One major advantage of electronic viewfinders over traditional optical ones is being able to see any adjustments made, such as white balance or exposure changes, in real time.

In short, a picture is taken. But it's not quite that simple. When you press the shutter, quite a few things happen inside the camera. In a traditional (D)SLR, when you press the shutter button, the mirror actually flips up, out of the way, to let the light information pass through and be recorded on the inserted film (one frame equaling 35mm) just behind the shutter. It then flipped down again. Depending on the available light, this either happens very quickly (milliseconds), or slowly (several seconds, or even minutes if the light level is very low). In photographic terms, this is called the Shutter Speed — the time interval of how quickly or how slowly the mirror flips up and thus the amount of time the shutter stays open during an exposure.

In a Mirrorless camera, there is no mirror mechanism inside. This saves space and weight. But with no mirror for viewing the image and blocking the light until you're ready to take an exposure, mirrorless cameras rely on an electronic shutter instead. Rather than flipping the mirror up and down to control exposure, the imaging sensor is simply turned on and off, thus limiting the exposure time electronically. This method has one drawback. When the sensor is turned on during an exposure, the sensor scans line by line sequentially. For normal subjects, this makes no difference, but for fast-moving subjects, rolling shutter distortion can be seen in the image.

As camera technology further advanced over the years, film was eventually replaced by a digital sensor inside the cameras, which again changed the game completely and revolutionized photography by propelling it into the digital realm. A sensor's main job (as 35mm film before it) is to record light information. A sensor does this through the conversion of photons of light into electrons (known as photoelectrons), which then get recorded as pixels, or light-sensitive elements on the sensor. Think of the sensor as the "soul" of a DSLR. It determines image size, resolution, low-light performance, depth of field, dynamic range, the types of lenses you can use, and even the camera's physical size.

One of the best parts is that with digital sensors you are no longer limited to just 36 exposures. With DSLRs and Mirrorless Cameras, you can snap away until the battery runs out of juice. Most photographers out there will tell you that this is both a blessing and a curse since you can now take hundreds, if not thousands, of pictures. That's fantastic from a technology standpoint, but more is not always better in an artistic fashion, and the old adage of "quality over quantity" still holds true.

The basic rules of composition, along with photographic technique, should always take precedence over the increasingly popular "spray and pray" approach of taking as many pictures as possible and hoping there's at least a handful of good ones amongst them.

DSLRs can last through a whole day of shooting and then some, while the mirrorless camera will be on at least their 2nd battery even halfway through the day.

Being an electronic device through and through, from the viewfinder to the shutter, it's no surprise that mirrorless cameras are much more power-hungry than their beefier brethren. Their screens — either in the viewfinder, or on the back of the camera — are turned on nearly constantly, and many mirrorless cameras feature some kind of built-in image stabilization. As such, they gobble up battery power. A DSLR uses lots of power only while reviewing images on the back screen, or when shooting in live-view mode.

Just as a comparison, a basic DSLR will offer up a bare minimum of 600 shots per charge, Digital Camera World notes. On a Mirrorless, you'd be lucky to get around 400 shots per charge. One reason for this is, of course, the battery size. One of the best things about mirrorless, namely their size and compactness, is also the culprit for smaller, less powerful batteries.

Of course, there are constant improvements to capacity and efficiency, but be prepared to carry several batteries with you for a whole day of intensive shooting with mirrorless cameras. One major advantage many mirrorless cameras offer, however, is that you can easily charge them by battery packs via USB ports.

Just to briefly touch on lenses here, the DSLRs have a clear advantage for lens choice simply due to the many more years DSLR systems have been around, and the ability to use old legacy SLR lenses as well. Some true gems can be found while perusing used camera stores. If we include available third-party options as well, the number of usable lenses is overwhelming.

Until fairly recently, mirrorless cameras were more or less restricted to their own maker's offerings, but now more third-party lens makers are latching on to the mirrorless market and giving customers a growing range of lenses to choose from.

Throw in adapters and you'll never run out of great lens choices. Putting a big, heavy lens on a small mirrorless body is still not a very good idea, however from both a handling perspective, in addition to the danger of possibly breaking the lens mount by putting too much stress on it.

It seems like everything is getting smaller and lighter all the time, and cameras are no exception.  The mirrorless cameras available now have significantly changed the photography landscape, and they may even replace DSLRs as the go-to for most photographers. The light(er) weight and compactness certainly make them fantastic travel cameras, and features like tilty-flippy screens, alongside In-Body Image Stabilization, are becoming the norm rather than the exception.

• smaller and lighter overall system
• many have tilty-flippy screens for social media vloggers
• more versatile video mode
• live histogram in the Viewfinder
• can immediately see the composition and final image exposure on the screen during night photography 
• better autofocus for video
• better manual focusing — especially helpful with older lenses via an adapter

The mirrorless variant clearly holds all the cards here.  They are lighter, smaller, have better autofocus in both stills and video, and can shoot nearly silently. Mirrorless cameras can usually fly under the radar and be less "intimidating" to others, offering a tremendous advantage in many professional situations from weddings to travel photography. I photograph many locations when traveling — some, where pro cameras are banned or require a special permit. There have been a number of times I've made it past the hawk-eyes of security in those places because my small mirrorless doesn't look "professional" enough. As a photographer, this inconspicuousness can be one of the best features for getting some great shots in amazing places.