How to choose a new lens for your digital SLR camera

So you recently purchased a new digital SLR camera and you have been having lots of fun shooting pictures with the included lens.  But you imagine that there must be a reason that you can buy more lenses for your camera, right?  So you start looking online hoping that a new lens might let you expand the capabilities of your camera.

If you are like most people, you will learn two things:

  1. New lenses are really expensive.
  2. Choosing a new lens is even more confusing than choosing a new camera.

Why is choosing a lens so confusing?

The popularity of digital SLR cameras is increasing at an amazing pace.  Every year, millions of new people buy high-end digital cameras.  Unfortunately, cameras and camera accessories are still named and marketed like the primary customers are scientists and optics specialists.  Camera models have weird, non-sensical names like “D7000″ or “60D” and lenses have even more confusing names like “Sigma 30mm f/1.4 EX DC HSM”.

But here’s the secret:

Camera model names really are just jibberish, but lens model names aren’t.

Digital SLR cameras have silly model names like Canon 5D or Nikon D7000.  These names don’t mean anything useful.  They are made up by the manufacturer.  Your only option is to either memorize them or consult a guide when you are looking for a new camera.

Unlike cameras, lenses have very useful names.  Typically the name of the lens is the scientific specification of the len’s capabilities.  If you can learn a little bit about lenses, you will be able to understand what all their names mean.  This will make it much easier for you to decide which new lens you should purchase.

Why do you need different lenses anyway?

In simple terms, a camera is just box that captures light.  Light comes into the box and is recorded as a picture by a light sensor.

Of course, the light sensor inside the camera isn’t “life size”.  It’s only a few inches tall.  So to record a full-sized picture of the real world onto the tiny light sensor, light from outside has to be “focused” onto it.

Different lenses focus the light differently.  Some lenses try to fit as much of the outside world onto the sensor as possible by capturing a “wide angle” view.  Other lenses try to capture far away objects by making them appear larger.

So why can’t one lens do everything?  Building lenses is a lot like building cars.  It’s easy to design a sports car to be light and powerful so that it can drive fast.  It’s also easy to design a mini-van that can efficiently carry a large group of people.  But it’s almost impossible to design a mini-van that is light and drives very fast.  Lenses are the same way.  It’s easy to optimize a lens to be good at one thing, but it’s impossible to make a lens that is good at everything.

Every lens is a compromise.  By learning about the differences between lenses, you will be able to find the right lens for the types of photographs you are making.

What makes lenses different

All lenses have two very important characteristics – the focal length and the size of the aperture.  These are the two most important things that determine what a lens can do.  There are also a number of other minor characteristics that will determine how well the lens works.  We will cover each of them.

1. Focal Length

The focal length of the lens determines how much the lens “zooms into” the scene.  A lens with a longer focal length magnifies the picture more.  A lens with a smaller focal length provides a wide-angle effect where more of the scene fits into your picture.

The focal length for digital SLR lenses are given in millimeters.  The millimeter measurement comes from the mathematical formulas involved in lens design.  You don’t need to worry about that.  Instead, you just need to memorize a few key numbers:

  • Below 35mm
    • This is a wide-angle lens.
  • Around 50mm
    • This is a “normal” lens.  The lens creates images that match what your eyes see in real life.
  • Above 85mm
    • This is a lens that magnifies or “zooms in” more than your eyes see in real life.

If you had a lens included with your camera kit, chances are that it isn’t limited to a single focal length. Instead, it covers a range of focal lengths by zooming in and out.  For example, the Canon 18-55mm lens covers the range from 18mm to 55mm.

So why not simply buy a lens that can zoom from 4mm to 300mm?  The problem is that it isn’t possible to build such a lens that makes good images and doesn’t weigh as much as a car.  In fact, fixed lenses that only have a single focal length are usually sharper and lighter than zoom lenses.  But they are also more limited.

There’s one final wrench to throw into this.  Many less expensive DSLR cameras have what is called a “crop factor”. Because it is less expensive to put a smaller image sensor in a camera, not all cameras have a “full frame” image sensor.  Since the camera’s image sensor is smaller, the lenses act differently on the camera.

If your camera has a crop factor, it will say so on the box or in the manual.  A typical crop factor is 1.6x.  When choosing a lens, you have to multiply this number by the focal length of the lens.  So while a 50mm lens is a “normal” lens on a full-frame camera, it acts like an 80mm lens (50mm x 1.6 = 80mm) on a camera with a 1.6x crop factor.

Thus if your camera has a crop factor, keep in mind that lenses will look more “zoomed in” than you would expect.  So instead of buying a 50mm lens to use as a normal lens on your camera, you might buy a 35mm lens because 35mm x 1.6 = 56mm (or about 50mm).

2. Size of Aperture

The other important factor to think about when buying a lens is the maximum aperture size of the lens.

Simply put, the aperture is the hole in the lens that lets light in.  The bigger the hole, the more light that comes into the camera.  So a lens with a bigger aperture is called a “faster” lens because it lets in more light and thus can shoot in less light.

The size of the aperture also controls “depth of field”.  The bigger the aperture, the less of the image that will be in focus.  If you aren’t familiar with depth of field, review our guide on shooting pictures in manual mode.

The aperture of a lens is written with an “f-number”.  Like most numbers involved in photography, the f-number scale is more confusing than it needs to be.  Just remember that the smaller the number, the bigger the aperture.

When you see the name a of lens like “Sigma 30mm f/1.4″, the part after the f is the f-number of the maximum size of the aperture for that lens.  Here are some common ones you will see:

  • f/1.4
    • This lens is very fast.  It is great for shooting in low light or for shooting portraits.  You will have excellent control of depth of field.
  • f/4
    • This lens is average speed.  It is great for most situations, but not low light.
  • f/5.6
    • This lens is not very fast.  It won’t work well in low light.  You also won’t have too much control of depth of field.

Since almost all modern lenses have an adjustable aperture, the f-number only specifies the maximum size.  A lens can always make the aperture smaller.  So an f/1.4 lens can also operate at f/4, f/5.6 or even f/22.  Thus a lens with a lower f-number is more flexible, but often heavier or more expensive.

Sometimes you will see cheaper lenses that have a “variable f-number” such as f/4-5.6.  This means that the lens can only operate at f/4 when zoomed all the way out.  When you zoom in, it can only operate at f/5.6.  In other words, the lens lets in less light as you zoom in.  This makes using the lens more difficult when you aren’t shooting in direct sunlight.

Extra lens features

When looking at lenses, the focal length and aperture by far the most important factors.  That is what determines what the actual picture will look like.

However, there are a number of other features that lens makers add to lenses to make the lenses easier to use in a variety of situations.  However, you don’t need any of these features to take good pictures.  Usually extra features mean higher prices.

3. Better Autofocus Mechanism

Different lenses use different technologies for autofocus.  Here are the major types you will see:

  • No autofocus
    • Older lenses or very specialized lenses may have no autofocus capabilities at all.
  • Micro motor autofocus
    • This is used on inexpensive lenses such as the Canon 50mm f/1.8.  It is loud and slower to focus.  You can’t manually adjust focus while in autofocus mode.
  • Ultrasonic motor (Canon)/Silent Wave Motor (Nikon)
    • This is used on more expensive lenses.  It focuses quickly and quietly.  You can adjust the focus manually even when using autofocus.  It is a higher-quality mechanism.

4. Image stabilization

Some lenses have an image stabilization mechanism.  Canon calls this IS or Image Stabilization.  Nikon calls this VR or Vibration Reduction.

This is a great feature to have.  Lenses with this feature can shoot sharp images in less light by compensating for the shake in your hands.  This feature won’t help you when using a tripod and should be turned off in those cases.

If a lens has IS or VR, it is going to cost more money.

5. Other Features

The more you explore lenses, the more types of specialized features you will encounter.

Some of the other features you may see are:

  • Tilt/Shift
    • These lenses can physically tilt and shift on their base.  They are designed for architectural photography.  They are very expensive and are meant only for a very limited type of customer.  A beginner should stay away from these lenses.
  • Lenses with removable optics
    • Some lenses, such as the LensBaby Composer, have removable optics that allow you to modify the characteristics of the lens by swapping out parts.  These are meant more for special effects, not for day-to-day shooting.  They are “fun toys”.
  • Manufacturer-specific terminology
    • Every manufacturer has an array of codes they assign to lenses for any number of reasons.  Sigma is especially bad about this.  In most cases, you can ignore them until you narrow in on a particular lens.
    • One code worth noting is that Canon adds an “L” to the name any lens that is “professional grade”.  These lenses also have a thin red line around the end of the lens so that everyone knows just how much money you spent buying them.  You will hear people refer to these lenses as “L glass”.
    • Most Canon lenses are “EF” lenses.  These lenses will work on any modern Canon camera.  However, a few very inexpensive lenses are “EF-S” lenses.  These lenses only work on crop sensor cameras.  You should probably avoid purchasing EF-S lenses if you plan to ever upgrade to a full-frame sensor camera.
    • On the Nikon side, all lenses are branded either “DX” or “FX”.  The DX lenses are crop-sensor only while the FX lenses will work on any Nikon camera.  Unlike the Canon EF-S lenses, the DX lenses are very common.  But if you ever plan to upgrade to a full-frame sensor camera, stick with FX lenses.

So what should you buy?

The lens you need entirely depends on the types of photos you want to take.

Indoor portraits (babies/children, parties, pets, etc)

If you bought a camera mainly to take pictures of your children, take pictures at parties or indoor portraits, you should consider a fast fixed lens.  This will allow you to shoot in low light while also getting a great depth-of-field effect.

The key here is to look for a lens in the 50mm to 85mm range with a low f-number.

Inexpensive suggestions:

  • Canon EF 50mm f/1.8 II – $100
    • This lens is called the “nifty 50″.  It’s the cheapest lens that Canon makes, but it takes great pictures.  Every Canon shooter should own this.
  • Nikon 50mm f/1.8D AF – $120
    • This is Nikon’s version of a “nifty 50″.  Every Nikon shooter should own this.

More expensive suggestions:

  • Canon EF 50mm f/1.4 USM – $350
    • This is a much nicer version of the “nifty 50″.  It has ultrasonic focusing and a much better build quality.  It’s worth the money if you can spare it.
  • Nikon 50mm f/1.4G SIC SW – $440
    • This is the ultrasonic focusing version of the above Nikon lens.  It’s worth the extra money for this version if you will be using this lens a lot.

Walk-around lens

A “walk-around” lens is a lens that you can keep on your camera most of the time.  It should have a fairly wide focal length range and work well in a variety of conditions.

Less expensive suggestions:

  • Canon EF 28-135mm f/3.5-5.6 IS USM – $420
    • This lens isn’t cheap, but it’s fairly inexpensive by lens standards.  This is a great all-around lens for basic use.  It’s not pro-level, but it will be sufficient for most people and it takes great pictures.  The addition of image stabilization is helpful in low-light scenarios.  It’s a great lens to pair with the Canon 50mm f/1.8 lens.
  • Nikon 16-85mm f/3.5-5.6G AF-S DX ED VR – $620
    • This lens is great for day-to-day shooting.  It has vibration reduction to help with low-light shots.  However, note that this is a DX lens so it won’t work well on Nikon FX cameras.
  • Nikon 18-200mm f/3.5-5.6G AF-S ED VR II – $740
    • This is another great mid-range walk-around choice for Nikon shooters.  This lens has a very wide focal length range and will work well for almost any situation.  This is also a DX lens, so it won’t work well on FX cameras.

More expensive suggestions:

  • Canon EF 24-105mm f/4 L IS USM – $1050
    • Good, versatile lens aren’t cheap and this one is no exception.  This lens is very sharp and works well in a wide variety of situations.
  • Nikon 24-120mm f/4G ED VR AF-S – $1300
    • This lens is a bit expensive, but it is sharp and works well in almost any situation.  Also, it is an FX lens, so it will work on all Nikon cameras.

Weddings and events

When shooting weddings, you need a combination of a fast lens with the ability to get close to the action.  This comes at a price.

  • Canon EF 70-200mm f/2.8L II IS USM – $2,070
    • This is the standard wedding shooter lens.  It has everything you need – a 200mm range to get you close to the action, an f2.8 aperture for low light usage and image stabilization to make sure your shots are sharp.  However, this lens is also expensive.
    • If you don’t care about image stabilization, Canon offers a cheaper $1,300 version of the lens without IS.
    • Canon also offers an even cheaper $1,100 version of the lens with an f4.0 aperture.  But if you are doing serious wedding shooting with indoor locations, you will need the f2.8 version
  • Nikon 70-200mm f/2.8G ED VR II AF-S – $2,170
    • On the Nikon side, this is your go-to wedding shooter lens.  It has everything you need – a 200mm range to get you close to the action, an f2.8 aperture for low light usage and vibration reduction to make sure your shots are sharp.  This lens works on both FX and DX cameras.  Since this lens was recently updated, you may also find the earlier version at a cheaper price.

Wildlife

For wildlife, magnification is the key.  The longer the focal distance on your lens, the closer you can get to the animals you are photographing.  Unfortunately, this means wildlife photography is an expensive hobby.

Cheap recommendations

More expensive recommendations

Keep reading! Here are a few similar how-to guides you may also enjoy:

  1. How to use a classic manual lens on your DSLR camera
    Shooting with old manual lenses on your new camera is a great way to experiment on a budget....

  2. How to choose a flash for your digital camera
    Picking a flash is pretty complicated these days.  Modern flash units are tiny computers with amazing abilities.  Both the Canon and Nikon flash systems allow flash units to communicate with the camera in real time.  Using wireless signals, all of the flash units fire a......

  3. How to choose a digital camera
    Unless it is your full time job, it’s almost impossible to keep up with the latest technology in digital cameras. New models are introduced almost daily.  Each new model continues to push the state-of-the-art forward at an amazing speed. And despite the fact that Apple......

  4. How to make the jump from automatic shooting to manual shooting
    Thanks to modern technology, a high-end digital SLR camera can be just as easy to use as any point-and-shoot pocket camera.  Taking a picture is simple!  Just set the camera on auto mode, point and shoot!  The camera takes care of everything else automatically.  Pretty......

  5. How to take amazing photos of your dog
    Since dogs are so commonplace, we often don’t think too much about them.  Most people think of dogs as fun pets who sometimes poop in the wrong place or eat things they aren’t supposed to eat.  Since they are so common, you might think that......