Congratulations! You’ve taken the truly giant photographic leap to an interchangeable lens camera. Sure, compacts have their place and moment but now it’s time to spread your picture-taking wings. What follows is a buying guide to your new camera’s most critical accessories – optional lenses.

Your First Step

We know you’ve done your most of your homework before purchasing your new camera. However, make sure you’ve checked out your camera lens options before pulling the trigger. We don’t expect you to buy 10 pieces of glass for your new camera body but whichever model you pick, make sure the manufacturer has an extensive range available – from wide-angle to telephoto and everything in between. And above all, make sure the various lenses you need for your personal photographic style are available for your system of choice.

When you buy an interchangeable lens camera you’re entering a relationship with the specific hardware mount determined by the brand. For example, Nikon uses the F and Nikon 1 mounts, Canon the EF and EF-S mounts (as well the less-popular EF-M mount for the EOS M mirrorless camera), Sony the A and E mounts, Panasonic and Olympus the Micro Four Thirds mount, Pentax the K mount, Leica the M mount, etc., depending on the type you choose. And while they are all interchangeable lens cameras, you cannot use Nikon glass on a Canon body and vice versa. Yes, we know this is common sense for many of you, but it’s really important you know your options.

Beyond the Basics

DSLRs and mirrorless cameras – particularly entry-level models – are often sold in “kits,” meaning they are typically supplied with a standard 18-55mm lens ranging from about 27-82.5mm in 35mm terms (more on that below). This may sound impressive but realize this is only a 3x zoom. Compare this to a compact $350 Canon PowerShot SX700 HS with a 30x zoom (25-750mm equivalent) and you’ll soon realize you’ll have to spend a lot to match that focal range. Comparing a DSLR to a point-and-shoot isn’t really fair since the quality and capability of interchangeable lens cameras is so much greater – never mind all the other pluses.

The Numbers Game

Now, get ready to use the calculator on your smartphone. Although a lens’ stated focal length may be 14-42mm, 18-55mm, 70-200mm, and so on, the actual angle of view that you’ll capture is impacted by the size of the imaging sensor. This is called the crop factor. In the case of most DSLRs and mirrorless cameras using APS-C sensors, this number is 1.5x or 1.6x. That’s how we got the 27-82.5mm 35mm equivalent for the aforementioned standard kit lens (18-55mm x 1.5). Now, this number varies with each make/model. Olympus and Panasonic Micro Four Thirds cameras have a 2x crop factor, Nikon’s 1 system has a 2.7x crop factor, the Pentax Q system a 5.6x crop factor, and so on.

So, why is this important? In the days of 35mm film, all cameras used the same-size recording medium, and so when looking at the focal length of a lens, the user immediately knew what angle of view it would capture. A 24mm lens was a super wide-angle, a 50mm was a “normal” lens, and a 28-70mm lens would cover everything from wide-angle to short telephoto. Nowadays, the only instance where the stated lens focal length is one-for-one are cameras with full-frame sensors, such as the Nikon D750, Canon EOS 5DS, or the mirrorless Sony Alpha A7 series. Since the imager is the size of frame of 35mm film, the lenses are direct equivalents in terms of how focal length relates to angle of view. Full-frame cameras provide wonderful image quality, but the price of entry is still pretty high at $1,299 and up.

Different focal lengths of digital camera lenses

When buying lenses for your new camera, you always have to keep in mind how the size of the sensor impacts the angle of view of the resulting images. Using a “nifty fifty” 50mm f/1.8 lens on a Canon Rebel T6i will not yield a “normal” angle of view, but a moderate telephoto equivalent to 80mm on film or a full-frame sensor due to the 1.6x crop factor. Likewise, on a Micro Four Thirds camera, a 25mm lens is not a wide-angle, but equivalent to a 50mm lens due to the 2x crop factor. A true wide-angle focal length would be a 14mm on Micro Four Thirds, and 18mm on an APS-C DSLR.

Zoom and Prime Lenses

The vast majority of interchangeable lenses are zooms. Their convenience can’t be beat, as one piece of glass offers a wide range of focal lengths. Beyond the basic 3x kit zooms there are 7x and 12x editions (also called super-zoom or telephoto) that we highly recommend. You’ll see figures like 18-125mm or 18-200mm, 55-210mm and so on. So multiplying the common crop factor of 1.5x for APS-C sensors, you can take wide angles of 27.5mm or 350mm telephotos (depending on your choice, of course). Having this flexibility is great since you don’t have to swap out lenses to capture the image you want.

Again, keep in mind that different system work with different sensor sizes and thus require different focal lengths. So depending on which system you use, you’ll find different focal lengths on the lenses. Typical Micro Four Thirds zoom lenses go from 14-42mm, while the kit zoom for Nikon’s 1 system goes from 10-30mm. Sony’s full-frame mirrorless cameras – the A7-series – use a 24-70mm kit zoom. The resulting angle of view that these lenses deliver, however, is roughly the same in all cases.
There are loads of zoom options; just check the manufacturer’s website for details and prices. And don’t be afraid to venture beyond the name on the front of your camera. There are third-party brands available (Sigma and Tamron, for example) that offer high quality, lower-cost options.
Prime lenses are also known as fixed focal length lenses. This type is typically for those who are fairly well-versed in photography (or for casual users looking to graduate to the next step). An example is a 50mm prime (such as the “nifty fifty” we mentioned above) that is well suited for portraits when used with an APS-C sensor, as it comes close to the classic 85mm portrait focal length. Again, this is our point of view but you could love 8mm fisheyes, 14mm wide angles, 60mm macros, or 500mm telephotos. Again, it all depends on your subject matter and style of shooting.

Some types of lenses aren’t available as zooms at all. The fisheye lenses we mentioned are one type, another are macro lenses. Some super-long telephoto lenses are also only available as fixed focal lengths. Another reason to go with prime lenses, besides having a specific style or vision, is the fact that prime lenses typically deliver better image quality than zooms, because they need only cover one focal length, and not a dozen. Also, prime lenses typically come with larger apertures that allow for more background blur (which is nice, for example, for portraits) and at the same time faster shutter speeds even in low light. With your standard kit zoom, you’ll have to start using the flash in instances where you can still work with available light when using a fast prime lens.

Open Wide

As you start searching for lenses you may do several double-takes when you start comparing prices. You may see one 50mm for $120 and another for $1,600 from the same manufacturer. The key difference is the aperture (or how wide open the lens can go); this is measured in f-stops – the lower the number, the more light you can capture. In the case of the $120 lens it’s f/1.8 while the more expensive one is f/1.2. The latter also uses higher-quality glass among other factors for the huge price differential. If you do a lot of shooting in low light without a flash, lower f-stops may be a crucial factor and a worthwhile investment.
Compare the numbers above – f/1.8 and f/1.2 – to the typical aperture sizes on a zoom lens that range from f/3.5 to f/5.6, and you’ll see that a prime lens with a large aperture often lets in two, three, four or more times the amount of light. One of the fastest lenses around is the 50mm Leica Noctilux lens rated f/0.95, which costs a cool $11K. Yes, that’s absurd, but we just want to show you the impact of wider apertures on lens pricing. There are, however, much cheaper options for fast prime lenses, especially for mirrorless systems such as Micro Four Thirds, with prices around the $1,000 mark.

Stay Steady

Many interchangeable lens cameras have image stabilization built into the body to help eliminate shaky shots. Any lens you attach to the camera will automatically be stabilized. Canon and Nikon – arguably the two largest sellers of DSLRs – both do not offer this. If you want stabilization, you have to buy specific stabilized lenses. This is easy enough to determine as Canon labels them IS while Nikon dubs them VR. Other manufacturers use a variation of this nomenclature but it’s an important feature – especially if you shoot a lot of extreme telephotos, or want to take pictures in low light without a flash
We’ve just hit the high points. As you enter the world of interchangeable lenses, you can delve deeper with research into glass quality and specific formulations. It can be a bit arcane, but as far we’re concerned you’ve already taken the biggest leap of all, simply by purchasing a DSLR or mirrrorless Compact System Camera. By all means don’t be intimidated, and have lots of fun.