How to downsize from a DSLR to a Mirrorless Camera

Over the last decade, the emergence of Digital SLR cameras have turned the photography world on its head. The amount of performance packed into the Canon and Nikon's latest mid-range DSLR models is astounding. Now, anyone with $600 can buy a camera that is good enough to take "pro" shots.

But as awesome as these cameras are, they aren't exactly pocket-sized and their goofy stylings don't encourage you to bring them along to restaurants or parties. But now that people have gotten a taste of DSLR quality, they don't want to go back to old-school compact cameras that take boring snapshots. This has led many enthusiats in search of something smaller and more fashionable that still offers DSLR-level performance.

Mirrorless Cameras

Camera manufacturers have responded in full force to this new demand for smaller 'pro-level' cameras. This has led to a new class of camera - the so-called "mirrorless interchangeable-lens" camera.

The Sony Alpha NEX-7 mirrorless camera is a lot smaller than your DSLR

A traditional DSLR camera uses a mirror to project light from the lens into the viewfinder. When you click the shutter button, the mirror flips up and light passes to the image sensor instead of the viewfinder. The flipping mirror is what makes that distinctive "click" you hear when you take a picture. This basic design has dominated the camera industry since the 1960s and the concept dates as far back as the 1860s.

Mirrorless cameras don't use a mirror to project an image to the viewfinder. Instead, they use digital viewfinders that display images directly from the image sensor. Recent advances in modern technology have greatly improved the quality of digital viewfinders making this a realistic alternative. The lack of a mirror makes these cameras smaller, more durable and much quieter. This allows camera makers to pack a lot of camera into a small package.

Matching DSLR image quality

DSLR cameras have large image sensors (the digital equivalent of film). A typical DSLR has an 'APS-C' image sensor that measures 25 x 16mm. High-end professional DSLRs have 'full-frame' sensors that are even larger - 36 x 24mm. A large sensor allows a camera to capture more light with less distortion and allows optics to be engineered that produce a shallow depth of field when desired. By comparison, point-and-shoot cameras and cell phones have absolutely tiny image sensors. For example, the image sensor in an iPhone 4S is a minuscule 4.5 x 3.4mm. No matter how well the iPhone 4S image sensor is engineered, it simply can't compete with larger image sensors due to the laws of physics.

A mirrorless camera attempts to put a large, high-quality image sensor into a small body. For example, the Fujifilm X-Pro 1 has a APS-C sensor and the Leica M9 has a full-frame sensor. These large sensors allow for great image quality.

The Fujifilm X-Pro 1 lets you control depth of field and shoot in low light like a DSLR but is portable enough to bring to a restaurant

Lens quality is also key to producing great images. The best lenses are optimized for one type of shooting because it is very hard to design one lens that works well in all situations. Point-and-shoot cameras have lenses that can't be switched out and thus can't be optimized for different shooting situations. Mirrorless cameras can be mounted with almost any lens, including great prime lenses that are designed to pack maximum image quality into a small and light package.

The Best Camera is the one you actually have with you

A popular saying is that "the best camera is the one that you have with you." The idea is that if you need a camera right now, your iPhone is a better camera than any expensive DSLR camera that you left at home.

A corollary to this would be "a camera that you want to bring with you is better than one you want to leave at home." The biggest advantage to using a mirrorless camera is that you are more likely to take it with you. While a Canon 5D Mark III may take beautiful pictures, it isn't going to fit in your pocket and you aren't going to take it with you to a dinner party. But mirrorless cameras are much smaller and less obtrusive. You can take one everywhere and always have it ready in case something interesting happens and you want to snap a photo.

But they aren't perfect

Despite all the good news, mirrorless cameras aren't right in all situations. There are still some cases where DSLRs have them beat.

Focus Speed

Most DSLR cameras use an autofocus technology called phase detection. Originally developed in the 1970s, phase detection autofocus has been continually improved ever since. DSLRs can focus nearly instantly and many have the ability to follow moving objects while autofocusing.

Phase detection autofocus is complicated and the details vary from camera to camera, but it typically uses a prism to split light into two beams which are then compared to determine focus. Most mirrorless camera designs can't accommodate this and instead rely on contrast detection autofocus. This usually means slower autofocus speeds and makes mirrorless cameras a poor choice for photographing fast-moving subjects.

However, contract detection autofocus is rapidly improving and some manufacturers such as Olympus have made significant advances in autofocus speed. Because contrast detection autofocus is so useful in small cameras, manufacturers are devoting R&D efforts to improving it and we are likely to see it catch up with phase detection autofocus in the next few years.

Limited Lens availability

Because there is no mirror, mirrorless cameras are able to use lenses that mount very close to the image sensor. This means that the lenses can be smaller, but it also means that these cameras introduce new lens systems that aren't compatible with the lenses you already own.

Most mirrorless lens systems are new to the market so they don't offer nearly as many quality lens choices as 30-plus year old Canon and Nikon lens systems. Leica is an exception with excellent mirrorless lens choices dating back to the 1950s, but the prices are out of the reach of most consumers.

Canon's DSLR lens line-up offers a lot more choice than the Fuji mirrorless lens line-up.

Most popular brands of lenses can be adapted to work with any mirrorless camera with an inexpensive adapter from Amazon. But as good as this sounds, it rarely works in practice. The adapted lenses usually lose the ability autofocus, may only work at one aperture setting, and tend to be so large as to negate the point of getting a smaller mirrorless camera.

Here's a Fujifilm X-Pro 1 mounted with a Canon 24-105 F4L lens. Compared to the smaller Fuji lenses, the Canon lens isn't very portable.

The Best Mirrorless Cameras

The traditional DSLR market is dominated by Canon and Nikon. But Canon and Nikon have been slow to innovate in the mirrorless market because they are scared to cannibalize their DSLR sales. This has left space for three companies who haven't been leaders in the modern camera market to step up in a big way. Sony, Olympus and Fuji have all released excellent mirrorless cameras and are, as they say, crushing it.

Micro Four Thirds system

The Micro Four Thirds system, a joint venture between Olympus and Panasonic, started the current mirrorless trend back in 2008. The Micro Four Thirds system uses smaller image sensors than newer systems like Sony and Fuji. But since it has been around for awhile, Olympus has been able to squeeze every ounce of performance out of the system and the latest models are really good. Also, lens selection is a little better for the Micro Four Thirds standard than some of the other newer systems.

The Best Micro Four Thirds camera: Olympus OM-D E-M5

The Olympus OM-D E-M5 is the best Micro Four Thirds camera produced so far. The only real disadvantage is that the smaller image sensor doesn't have quite the image quality as the competition. But Olympus makes up for it with an excellent focusing system that is faster and more accurate than Sony's and Fuji's offerings.

Sony NEX E-mount system

Introduced in 2010, the Sony NEX E-mount system was originally aimed at the beginner still and video camera market. They original NEX models sold very well but they didn't offer advanced features. Sony addressed this with the release of the Sony NEX-7.

Sony's Top-of-the-line: Sony NEX-7

The Sony NEX-7 is Sony's "pro" mirrorless camera. It has fantastic image quality and is really popular with photographers who want to mount old lenses to newer digital camera bodies.

However, the NEX E-mount system was originally created for beginners and the early lenses aren't up to the same image quality standards as the NEX-7. So while there is a wide selection of E-mount lenses, only a few of the newer ones offer superior image quality. But this will surely improve over time as Sony releases new lenses.

Fujifilm X-mount system

Fuji took everyone by surprise when they released the Fujifilm X100, a beautiful but oddly limited and very expensive compact camera. Fuji further shocked everyone when the camera was a huge hit. Two factors made the X100 a success - amazing image quality and fantastic physical design (something that is sorely lacking from many modern cameras).

Fuji's Boutique Stunner: Fujifilm X-Pro 1

Fuji followed up the X100 with the X-Pro 1, a larger, interchangeable lens camera. Like the X100, this is a boutique camera and it offers amazing image quality and design. But it isn't perfect. In particular, the focusing can be a bit slow and the lens selection is still very limited. It's also expensive relative to the offerings from Olympus and Sony.

One unique feature of the X-Pro 1 is that Fuji offers a high-quality Leica lens adapter that integrates into the camera's software. So if you ever wanted to use Leica lenses but didn't want to spend $7000 on a Leica camera body, the X-Pro 1 is a great choice.

Leica M system

Unlike these newcomers, Leica has been making mirrorless cameras since the 1940s. And when measured on pure quality and craftsmanship, they do it far better than anyone else. Their lenses are some of the best compact lenses ever made. But these days, Leica seems more interested in releasing ever-more-expensive limited edition camera reissues than improving their digital technology.

Aging Luxury: Leica M9

The Leica M9 is a beautiful camera manufactured to exacting standards. And unlike everything else on the market, it is a true rangefinder camera. However, it uses a 2009-vintage full frame image sensor that performs beautifully in bright light but can't compare to newer technology in low-light situations. And as a rangefinder, the Leica doesn't offer any autofocus at all. It's purely a manual affair.

If you have an unlimited budget and love old lenses, the Leica may be a good choice. But at price that is more expensive than the other three choices combined and with aging image sensor technology, not many photographers are willing to make the leap. Hopefully Leica will release a new model soon with updated image sensor technology and regain its throne as the ultimate high-end choice.


Mirrorless cameras are just getting started, but they are already amazing products. And as manufacturers continue to improve on their limitations, traditional DSLRs may become a niche product reserved for specialized applications. But just like when you buy a DSLR, when you buy a mirrorless camera you are really buying into a lens system. So before you buy, think long and hard about the types of lenses you want to use and pick the system that you are willing to stick with.