Photo Tip Tuesday – Lenses

You’ve chosen a type of camera, selected your brand and have decided the capacity of your memory card. But you can’t start shooting until you have a lens!

DSLRs and mirrorless cameras — particularly entry-level models — are often sold in “kits,” meaning they are typically supplied with a basic zoom lens, which may be something like an 18-55mm or 14-42mm, depending on the brand and format of your camera. One common misconception about large, interchangeable-lens models is that they offer better zoom capability than a compact camera. In fact, the opposite is often true; an 18-55mm lens is only a 3x zoom. Compared to a compact camera like the Canon PowerShot SX730 HS, which has a 40x zoom (over 13 times the zoom power of a DSLR kit lens), this is nothing.

Typically, the maximum zoom power you’ll find in an interchangeable lens is around 10x, but comparing a DSLR or mirrorless camera to a point-and-shoot isn’t fair. DSLR and mirrorless cameras use much larger sensors that produce very high quality images compared to compact models, but those large sensors require equivalently larger lenses. This is why small cameras can have a larger zoom range while larger cameras will rely on multiple lenses to cover the same range.

Figuring out which lenses will suit your specific needs is not always easy. There are several abbreviations and specifications you need to know, and different manufacturers use completely different abbreviations for the same properties.

Aperture

Maximum aperture is stated on all lenses. It tells you how much light the lens can get through to the sensor at its best. More light means you can keep shooting in darker conditions without the image blurring due to camera shake. Aperture is provided as an aperture number, such as f/2.8 (or sometimes 1:2.8). The smaller the aperture number, the more light entering the camera. Typically, the lenses with the widest aperture offer a maximum aperture of around f/1.2. Most consumers will be satisfied with an aperture number of between f/2.2 and f/3.2. Generally, the higher the aperture number, the cheaper the lens (telephoto lenses often have larger aperture numbers).

On zoom lenses, there are usually two aperture numbers (for example, f/2.8–f/5.6). The smaller aperture number indicates the amount of light you get with the widest angle, while the larger shows how much light you get at the maximum zoom.

Focal Length

The focal length is given in millimeters and specifies whether the lens is a wide-angle or telephoto. Both have their advantages and disadvantages:

With a telephoto lens, you’ll naturally get closer to subjects far away. Telephoto lenses are also preferred for portraits as they protect the facial proportions better than a wide-angle. With a telephoto lens, it’s much easier to get a blurred background (bokeh) since telephoto lenses have less depth of field than wide-angle lenses. Telephoto lenses usually have lower brightness and are more vulnerable to blurriness during the shoot if there is any camera shake. Telephoto lenses are usually physically larger than the wide-angle lens as well.

Wide angle lenses, on the other hand, are suitable for nature photography when you want to capture more of the landscape. They’re usually good in both brightness and depth of field, and are usually physically smaller and lighter than telephoto lenses. On the negative side, the wide-angle lens is not ideal for photographing people, at least not in a pure portrait context. A wide-angle gives an impression of greater distance between what is close and what is distant (which can make the subject look like they have a bigger nose or sunken eyes). There’s also a higher chance for distortion with a wide-angle lens as the straight lines begin to bend into the edges of the image.

The cross between a wide-angle and a telephoto lens is called a normal or standard lens. This is a lens that renders the environment as we see it with our own eyes (in relation to distance and magnification). In the 135 format used for still photography, a normal lens is 50mm. Everything with a smaller focal length is called a wide-angle, while larger focal lengths are called telephoto.

On regular compact cameras, the focal length usually extends from 35 mm to 105 mm (according to the 135 format). It’s important to remember that focal length is connected with the size of the camera’s image sensor, allowing the focal length of a lens to change depending on which camera it is used on. To avoid too much confusion, it’s common to explain the focal length equivalent to the full-frame DSLR camera.

Zoom Lenses

Most DSLR kits come with a zoom lens — the most versatile lens in the bag. My Nikon D5200 was equipped with an 18–55mm (similar zooms are available from other manufacturers). At its shortest focal length (18mm), it is a relatively wide-angled lens which makes it a good lens for shooting scenery and groups of people. At its longest focal length (55mm), it serves as a portrait lens, allowing you to pull in close to the face of your subject from several feet away. The beauty of a zoom lens is that you can adjust it from wide to telescopic with the turn of a dial.

Zoom lenses come in a variety of configurations that overlap considerably with other lens categories. Wide-angle zooms can cover focal lengths from 10mm to 24mm. Telephoto zooms can cover 55mm to 200mm, or 200mm to 400mm. You can even get a super-flexible zoom lens that ranges focal lengths from 18mm to 300mm. Sounds perfect, doesn’t it? But there is a downside: that flexibility generally comes with added complexity, weight and cost. For instance, a Canon EF 28–300mm lens weighs 3.7 pounds and costs $2400, enough to break the budget of most amateur photographers.

Prime Lenses

A prime lens has a fixed focal length and is optimized for a certain type of photography. Available from 10.5mm all the way up to 600mm, primes are simpler in construction and generally lighter than zooms. Plus, they tend to produce better images.

Consider this comparison: At its maximal focal length, Nikon’s 18–55mm kit lens has an aperture of f/5.6. A NIKKOR 50mm prime lens (which we photographers lovingly call a Nifty 50), is shorter and uses bigger glass, so it has an aperture of f/1.2, f/1.4 or f/1.8 (depending on which one you purchase). The lower f-rating means more light and greater control over depth of field, yielding crisper, more powerful portraits.

Wide Angle & Telephoto Lenses

The lower the focal length, the wider the field of view – anything under 35mm is typically considered wide-angle. These lenses are useful for photographing interiors, where you can back up only so much before hitting a wall. But super wide-angle lenses can cause distortion toward the edges of photos. A well-designed lens can fight such distortion.

Some extreme wide-angle lenses, called fisheye lenses, don’t fight distortion at all; instead, they take advantage of it. The effect can be pretty dramatic (see: Busta Rhymes’ “Put Your Hands Where My Eyes Can See” video).

Telephoto lenses, however, act like telescopes. When you magnify a distant object, however, you also amplify any movement of the camera itself, so image stabilization technology or a tripod is a must.

Macro Lenses

If a telephoto lens is like a telescope, a macro lens is like a microscope (great for taking closeup shots of flowers, insects and other small subjects). A macro lens’ best quality is its ability to maintain sharpness at high magnifications. High-quality macro lenses can achieve 1:1 reproduction, meaning the subject matter can be captured by the camera’s sensor at life size.

Lenses can become an expensive habit. Off-brand models may save you cash, but my experience so far has shown that with optics you generally get what you pay for.

Crop Factor

Various camera manufacturers use different sizes of image sensors in their SLR cameras. This can cause confusion in relation to figuring out the actual capacity of a telephoto or wide angle lens. The most common trick is to convert the focal length to the full frame equivalent. To make the conversion, you need the crop factor. For example, on Canon’s SLR cameras without a full frame sensor, the crop factor is 1.6. This means that you must multiply the focal length by 1.6 to determine what it would have been on the 135 (full-frame) format. A range of 18–55 mm will be approximately equal to 29–88 mm. Here are the crop factors on the 4 main manufacturers:

Nikon – 1.5
Canon – 1.6
Pentax – 1.5
Sony – 1.5

Image Stabilization

Although you’ll find optical image stabilization in most DSLR camera bodies, major manufacturers continue to use stabilization in the lens. This is done by moving the elements in the lens, thus eliminating camera shake. However, manufacturers such as Olympus, Pentax and Sony all use image stabilization in the camera body, so you won’t find lenses with stabilization from those suppliers. Below, you can see the abbreviations other manufacturers use to specify that their lenses have built-in image stabilization:

Nikon – VR
Canon – IS
Sigma – OS
Tamron – VC

Color Refractive Correction

Photography focuses entirely the light. However, the different colors of light bend differently when they pass through a lens. This can lead to color shifts, particularly toward the edges in an image. To counteract this, manufacturers use what they call a low dispersion glass. Below are the abbreviations you would see on the lenses using low dispersion glass:

Nikon – ED
Pentax – ED
Sigma – APO
Tamron – LD

Crop Image Sensors

After SLR cameras took the step into the digital world, image sensor had to be modified because it has a much smaller area than a traditional negative. Since the image surface is smaller, lenses can be made smaller and lighter. However, these lenses cannot be used with traditional film cameras or DSLRs with a full frame image sensor. Below are the abbreviations you would see on the lenses using a crop sensor:

Nikon – DX
Canon – EF-S
Pentax – DA
Sony – DT
Sigma – DC
Tamron – DI-II

Full Frame Image Sensors

The manufacturers also make lenses for full frame image sensors. These can also be used on regular film SLRs. Below are the abbreviations you would see on the lenses using full frame sensors:

Nikon – FX
Canon – EF
Pentax – FA
Sigma – DG
Tamron – DI

So, when it comes to choosing the lens (or lenses) that are right for you, make sure you take your subjects, you amount of light and the focal length into consideration. It’d be quite difficult to photograph a wedding with only a 400mm f/5.6 lens!