There are a variety of lens types for photographers to use: fixed, zoom, macro, and combinations of fixed and zoom lens with macro capabilities. Let’s examine the differences among them.
- Fixed focal length lenses
- Most true macro lenses are of fixed focal length, that is, they don’t zoom. Macro lenses are the most highly corrected lenses a manufacturer makes. In making a zoom, there are more optical tradeoffs in the design. For the absolute highest quality, a fixed macro lens is the best choice. They will usually focus to 1/2X or even to life-size.
- Zoom lenses
- There are many zoom lenses that claim to be “macro” lenses. These lenses usually only focus to about 1/4X reproduction ratio, which is not as close as the true macros. Zoom lenses frequently have variable apertures, which is ok if you shoot on program mode. For manual exposure, however, this means that at different focal lengths, you will have to readjust your shutter speed as you zoom. Zoom lenses have the advantage of allowing you to move closer or farther away without actually moving your tripod or camera. Zooms are also usually slower (have smaller wide open apertures) than fixed lenses.
- Macro lenses
- As already mentioned, macro lenses can be either fixed or zoom lenses, but the best quality is in the fixed lenses. These macro lenses are designed to be at their optical best at close focus. A traditional lens is optically best at medium distances. Most macro lenses will have maximum apertures of about f 2.8 or f 4, which is slower than traditional fixed focus lenses which are often between f 1.4 and f 2.8.
- Internal focusing lenses
- The simplest way for a lens to focus closer is to physically move the entire lens farther away from the film plane. This is the method used in most middle range fixed focal length lenses. Another method was developed where certain groups of smaller elements inside the lens move relative to the lens case, and adjust the focus of the light reaching the film. This is called internal focusing (IF), and is much quicker and easier for the photographer to focus.
500mm Mirror Lens
A 500mm mirror lens is short and lightweight to carry, but it has some drawbacks. Classic symptoms of a photograph taken with a 500mm mirror lens are all the small highlights in the out of focus background or foreground becoming small donut shaped circles. In this picture of a female big horn sheep, the background is filled with donut shaped highlights.
Other advantages of an IF lens include a front element which does not rotate, so use with a polarizer is simplified. There is no need to keep readjusting it when you focus nearer or farther. The other advantage is that you don’t lose light from extension when you focus, so IF lenses are brighter than other lenses when focused close. This is a plus for macro lenses, and the newer macro lenses are often IF lenses.
- Long Lenses
- There are two ways of getting “up close and personal” with long lenses. The best way is to used a fixed focal length lens of extreme magnification such as a 500mm or 600mm. The best of these feature a maximum aperture of f 4, providing plenty of light for low-light wildlife and nature situations. Another alternative is a mirror or catadioptric lens. This is a camera lens which uses a pair of circular mirrors inside to fold the light path and reduce the size of the lens. Compare the two lenses in the photo; the larger lens is a 500mm f 4 conventional lens, while the smaller is a 500mm f 8 mirror lens. The conventional lens weights about 10 times as much.
Mirror lenses are cheaper and lighter to carry, but they have some serious drawbacks. They feature a fixed aperture, usually f 8 or so, making low-light exposures nearly impossible. The mirror also highlights bright spots and turns them into “donuts” in your image. For serious nature photography, invest in a good quality fixed or zoom lens to increase your magnification.
There are reasons other than magnification to choose a particular lens. One of the most important of these reasons is the change of perspective afforded by using lenses of different focal lengths.
A wide angle lens sees a wide angle of view. The first thing people think of is that a wide angle lens will let them include more of a scene in the image, and this is true. What they don’t consider, however, is what the short focal length will do to the appearance of the subject. If you were to make a head and shoulders portrait of your best friend using a 20mm lens, you would have to stand a distance of about a foot (30 cm) away from him. At this distance, his nose would be much closer to the lens than his ears, and so the nose would be much bigger proportionally than the ears in the photograph. This is generally not a flattering effect, and so we don’t use wide angle lenses to photograph closeups of people. The same effect happens when we photograph flowers closeup with a wide angle lens. The parts of the flower that are closer to the lens appear proportionally bigger in the resulting photograph than the other parts of the flower, or than the other flowers in the picture. A wide angle lens will cause objects closer to the lens to appear proportionally larger in the photograph than the other objects in the picture. This is useful for separating an object from surrounding objects, making the objects appear farther apart. Wide angle lenses seem to expand space.
Telephoto lenses magnify objects. More than this, however, they affect the appearance of objects in a photograph. Using a 100mm lens to make the same head and shoulders portrait of your friend as you made with the 20mm lens, you would have to stand back about 10 feet (3 or 4 meters). At this distance, the nose and ears are all approximately the same distance from the lens, so there is no apparent distortion of perspective. The person will appear as we expect him to appear, because we’re used to seeing people from across a room. We don’t usually see people from extremely close up, and so the view from the 20mm lens seems strange to us. If there are other people in the picture, they will also appear normal.
If we move to a very long telephoto lens, like a 500mm or 600mm lens, we would have to move backward 25 or 30 feet (10 meters) to photograph our friend. The magnification power of this lens is high. A person standing a few feet behind him would appear to be nearly at his side, because the difference of a few feet compared to 30 is small. The large telephoto lens has a perspective that seems to compress space, magnifying distant objects equally.
We can use this difference in perspective between lenses to our advantage. Any time we want to separate a foreground element from a background, we can use a wide angle lens. Any time we want two objects to appear close together, we can use a long telephoto.
The background is an important part of any photograph. A wide angle lens has a wide angle of view. That means that it will include a large amount of background behind the subject. Everything, from the mountains to the trees to the parking lot with all the cars can appear in the background of a wide angle photograph. A telephoto lens, however, has a narrow angle of view. That means that it sees a smaller amount of background behind a subject. By using a telephoto lens, we can choose the part of the background that we want behind our subject, excluding everything else. For this very reason, a 200mm lens is a much more useful lens for closeup work than the more common 50mm lens. A 500mm lens is much more useful for wildlife photography than a 200mm lens for a number of reasons, but one of the most overlooked is its ability to control the background. Control of the background is essential to good photography.
- Lens Magnification
- Gather your lenses together and go out in the field with several rolls of film. Choose a subject and sit in the same spot and photograph it, just changing lens, getting progressively longer with each lens. Take notes. Examine the background and foreground, as well as the size of the subject within the frame. What changes as you get closer or further away?
- Lens Perspective
- Now, repeat the previous exercise, but this time, keep the subject the same “size” in your viewfinder, moving closer or further back as you change lenses. How does the background and foreground change as you move to or from your subject with the different lenses? Take notes and match them with the final results.
- Spend a Day With a Lens
- Take one lens from your collection and spend the day with it, or at least a few hours. Go to a local park or natural area and photograph only using that lens. Find out how close it will focus to a subject and test its “infinity” spot by doing a sweeping landscape. Take at least two rolls of film with that lens and then go home. With your notes, consider the results to study and learn how that lens sees, its weaknesses and strengths. Do this again with your other lenses (only one per day) and write this information down on a chart, comparing the strengths and weaknesses of each lens. (For example, mirror lenses make donuts circles of bright highlights, so photographing a subject with bright highlights with that lens makes unattractive pictures. Extreme wide-angle lenses tend to curve closeup lines like along a building, so unless you want that effect, this isn’t a good idea.) When you learn how your lenses see, you will automatically know which one to reach for when a subject pops into view.
Close Focusing Distance
Almost every lens made will focus to infinity and can be used for scenics and people and just about anything else you would want to point it at. But at some point, it just won’t
|Lens||Closest Focusing Distance|
focus any closer. For the average 50mm lens, this might be about a foot and a half away. For a 200mm zoom, the close focus distance might be 4 feet, and Nikon’s 500mm f4 telephoto will focus no closer than about 15 feet.
Macro lenses are designed to photograph small things, close things. Nikon’s 55mm macro lens will focus to about 5 inches, and their 200mm manual focus macro will focus to about 20 inches, much closer than their traditional counterparts. If you photograph lots of small things, there are other options, but it might be worth your money to get a macro lens.
Study these two pictures carefully. Which length lens took each picture? Was it a 55mm? Or a 200mm? A 300mm or 500mm? Maybe it was a 20mm lens? Can you tell which lens took which picture?
Answer: Any lens could have taken these pictures. The top one is done with a 200mm lens and the lower one with a 55mm lens. Both lens see the same picture, but they require different distances from the subject to equal their magnification. Longer lenses can give the same closeup results but with a greater working distance. The benefits of a greater working distance is space between you and your subject. If you are photographing a flower, this might not matter, but if you are photographing a poisonous snake, you might want to keep your distance while keeping the subject the same size in your viewfinder.
For most subjects in nature, the distance your camera is from the subject won’t influence the subject. But photographing insects, butterflies and such, can be difficult because they are exceptionally attentive to your location and will respond accordingly – often by escaping the situation. Being able to get close and still maintain some distance becomes critical then. Add to this the challenge of low light, and the closer you are to the subject, the greater the chance of casting a shadow.
By using longer lenses, your distance from the subject and the camera increases. This is called the working distance. Working with live creatures, this distance is critical. Either way, it’s nice to have some room between the camera lens and the subject. Here are some examples of working distance based on the closest focusing distances of typical lenses.
- Measure the Distance
- How close will your different lenses focus? Check with your manual and then check it yourself by picking an inanimate subject and photographing it as close as you can by manually focusing the lens and measuring the distance. Do the measurements match? If you have a point-and-shoot rangefinder style camera, measure to the recommended minimum distance and then take a picture. Then move forward a bit in two stages, taking pictures at each point (and measuring), and then repeat this moving back in at least two stages from the starting point. When you get the picture back, check closely to see at which point the image was really in focus. This will be your closest focusing distance.
- Working Distance
- Compare the closest focusing distance of each of your lenses to create a chart of how close each lens will focus from a subject.
- One Subjects, Two Lenses
- Duplicating the section “Which lens took this picture?”, choose an inanimate subject and photograph it with at least two different lenses (or focal lengths) keeping the subject at the exact same size in each picture. Note how much working distance you have between the subject and the lens.
The most common lens accessory purchased is a teleconverter, also known as a doubler or multiplier. A teleconverter, or multiplier, is a group of glass elements in a small lens casing which can be inserted between the camera and the lens to magnify the image. They are available in 1.4X and 2X magnifications, and some manufacturers even offered a 3X. When a lens is used with a teleconverter, its focal length is multiplied by the magnification factor. A 100mm lens with a 1.4 or 2X teleconverter becomes 140mm or 200mm, for example. The advantage, besides magnification, is that they can be used for far off subjects and macro subjects equally well. And your lens will still focus to the same close range as before.
The disadvantage is that the maximum aperture is reduced by the magnification increase. A 1.4X teleconverter costs 1 stop of light, and a 2X costs 2 stops. So an f 2.8 lens becomes f 4 or f 5.6 with a 1.4X or a 2X, respectively. Light loss makes focusing more difficult, and results in slower shutter speeds. There is also a slight loss of quality with the use of a teleconverter, but if a quality prime lens is used, the loss should be negligible.
We recommend using the same brand teleconverter as the lenses you use, since the manufacturer designs them to work well together. Use Canon with Canon, Tamron with Tamron, etc. And be aware that some lenses will not autofocus when a teleconverter is installed.