Buying a lens can be confusing. What is a prime lens? Are good lenses available on a meager budget? Is a zoom lens a good choice? Let’s look at what kind of lenses you should consider and how a wise investment in a quality lens can be the difference between your audience reacting with a wow or a yawn.
We know talking about buying DSLR camera lenses makes your mind get all fuzzy, but let's get focused and zoom in on buying the right lens for your specific needs. It doesn't have to cost a lot of money, but there are times when you're not spending money but investing in quality lenses that last and produce crisp, bright images.
An often forgotten element of video producing, lenses play a vital role. Average to good lenses are seldom given positive attention, while horrible lenses attract the wrong kind of attention: the "Why does my video look like it was shot through a soda bottle?" attention. Purchasing quality lenses can help avoid this issue.
For nearly all consumer camcorders, lenses are attached and can't be interchanged with other, specialized lenses. You're pretty much stuck with the lens that came with the camera. That's not to say it's a poorly performing lens, but your options for versatility are greatly reduced when some special situation calls for a shallow depth-of-field or a very wide view of a given area. However, when shooting video with a DSLR or one of the newer camcorders with interchangeable lens options, your available choices grow greatly. No longer are you limited to the manufacturer's lenses, you may shop for lenses created by Chrosziel, Rokinon, Sigma, Tamron, Zeiss, and others that specialize in making lenses that provide combinations of quality, cost and ability.
Terms and Specifications
Before you begin surfing the Web or pawing the merchandise at your local camera shop, you should know a few definitions so you can talk and shop for lenses with educated confidence. Also, you'll be more aware of the capabilities of camera lenses and how their specialized uses apply to you and the tasks you have in mind, so you can be a better consumer.
First up is the prime lens. Some define a prime lens as the one used most often in their DSLR camera kit bag. However, we'll use the traditional meaning of prime lenses as those with a fixed focal length. This means the lens elements cannot move within the barrel of the lens itself and does not zoom. While this seems limiting, prime lenses are less complicated, have fewer parts and are designed for highly specific tasks like close-up photography. Due to the simpler construction, they tend to cost less and suffer from fewer instances of optical aberrations or problems with the raw image.
Zoom lenses are more complicated than prime lenses. They have more demands placed on them than prime lenses because they are expected be the one-stop solution for most shooting situations, from wide angle to zooming in on faraway subjects. While useful, zoom lenses are a compromise. They're not designed to be a dedicated close-up wide angle lens nor a dedicated long-range device and they can't do the same precise jobs as well as a prime lens. Zoom lenses are at the mercy of the manufacturer's choices regarding lens capabilities and build quality. Zoom lenses contain more parts, cost more money to engineer and build, and weigh more with an inconveniently long length, which can become wearisome to carry over the course of a long day.
Consider the photographic lenses' maximum aperture when lens shopping too. Aperture is the size of the "window" the lens has when open at its widest setting. Think of an aperture like a window: larger windows allow more light into the room. The same idea applies to camera lenses. Generally, the larger the aperture, the better. Remember, the aperture is designated by numbers (f1.8, f3.5, etc.), but in the case of aperture, a smaller number means the potential opening is bigger. This has to do with a mathematical formula for the amount of light doubling. So, if you see a very low aperture number when shopping, the lens should be capable of low-light capture.
Focal length is measured in millimeters. Focal lengths for consumers are often no more than 300mm. Common variable focal length camera lenses can be found in the 28-50mm lenses often sold as standard equipment with many cameras. Keep in mind that as the lens zooms in, the width of the image shrinks. So, the side-to-side distance, called the field of view, shrinks too.
Practical Uses for Focal Length Lenses
One way to understand the concept of focal length is to explore the best uses for those lenses.
For ultra wide use, lenses with a focal length of 24mm or less are ideal. As discussed, the short focal length presents a very wide field of view. This is ideal for projects like photos of a sweeping vista, real estate sales, macro shots (like a bee on a flower). The short-barrel prime lenses also allow lots of light to strike the sensor within the camera, creating sharper detail and contrast.
Lenses that are 24-35mm are defined as wide-angle. While these don't have the angle of view that an ultra-wide lens does, they still serve a useful purpose as a tool to capture landscapes, great numbers of people and expansive views of interiors like museums and art galleries. By definition, these small focal lengths lenses are not zoom lenses, so the best way to get close to an object is to use your legs - safety and common sense permitting. Also, note that, unlike a fisheye lens, the wide angle of a 35mm lens will not bend and distort the edges of the image. All lines will stay straight. This will exaggerate any mistakes in composition, so click away carefully.
Lenses in the 35, 50, 70mm classes are considered "normal" lenses. The 50mm range approximates the human eye closely and photos taken at this focal length look just like the image you saw with your own peepers. This lens normally has a minor zoom range, so it's a great choice for tasks like casual portraits, and other types of shots that don't require an extremely wide angle or zoom of any great focal length.
Between 70-300mm, the label on the lens changes from normal to telephoto. Faraway objects can be brought visually closer and provides framing options unavailable with a wide angle lens. Common uses for a telephoto lens include sporting events, aerial videography, nature/animals and any need to bring something far away much closer. As the focal length of the camera lens grows, the lens barrel grows too, as does the weight. Keep this in mind and question if you really need that heavy zoom lens before bringing it around the county fair all day.
Beyond 300mm is considered to be a super telephoto lens. Any thought of using a zoom lens this long as a substitute for a wide angle lens is pure folly, as most telephoto lenses act like prime lenses while permanently zoomed to their maximum focal length. Sports photographers are common users of super telephoto lenses. Normally very heavy, supertelephoto lenses are best used with a tripod supporting the camera or a monopod mounted to the lens itself. Steadiness is paramount because telephoto lenses greatly magnify even the tiniest handheld movement.
A low-cost zoom lens will be made from plastic and some have plastic lenses within the barrel. Optical aberrations may be visible in those images. A slightly bigger budget will produce a commensurate increase in quality and materials and reduce optical aberrations.
Which lens do I use for...?
Shallow depth of field: A shallow depth of field allows objects to be in sharp focus while everything in front of and behind that object appears fuzzy and out of focus. This effect is effective for portraits and commercial photography. If this kind of effect appeals to you, use a long focal length lens like a 300mm telephoto zoomed to the max, but make sure the framing of your subject is satisfactory. Open the aperture as wide as you can and the depth of field will be very narrow.
Deep depth of field: The opposite of above, a deep depth of field means everything from near to infinity is in sharp focus. A prime lens, such as a 24mm wide angle lens is best for this kind of shooting. In fact, the shorter, the better. Aperture size is not as crucial because a small aperture still allowing plenty of light will often return impressive results. Experimentation will reveal the most effective combinations of wide angle lens, aperture and sensors. Landscape photographers use this method to ensure as much of the scene as possible is focused and crisp.
Low Light: Film speed used to matter, but since the DSLR has taken root, lenses are now the main consideration for low light videography. Quality lenses are imperative to ensure as much light as possible gets into the lens and strikes the sensor in the DSLR. A prime lens is ideal, as is a tripod because low-light videography may require more gain, and thus, noise, all while keeping the camera secure with the aperture open wide.
People ask: What lenses do I need to be a good videographer? The answer is: no lens will make you a good videographer. Practice and motivated self improvement are the most instrumental at that. However, a smart consumer buying quality lenses for a DSLR can make a good videographer, a better videographer.
Want to impress your buddies? Here's a term to throw around: crop factor. Put simply, crop factor was originally used during the transition from film to digital cameras as a way to explain how lenses designed for 35mm film would be affected by the smaller digital sensors of early DSLR cameras that still had film SLR lens mounts. Crop factor uses a mathematical formula to explain how formerly-film lenses change the field of view to "act" like a zoom lens. For instance, a 50mm film lens with a crop factor of 1.5 would, on a digital camera, "act" like a 75mm lens does on a film camera.
Got it? Good, because there's a test on this next week.
Randy Hansen is an award-winning videographer with more than 23 years in television news and corporate video. He lives with his wife and two kids in Dallas.