Zoom Lens

A Zoom Lens is a camera accessory that allows a photographer to take close-up shots of his subjects. Similar to a telephoto lens, the zoom lens can magnify a subject anywhere from two to up to twelve times its original size.

While a zoom lens can be used at close range for macro photography shots, it may also be used by a photographer to capture shots of subjects at a far distance from the camera. Using the zoom lens for distant subjects can allow the photographer to take pictures of subjects or scenes that he can’t access for security reasons or because the action of the scene is too dangers.

For this reason, zoom lenses are commonly used in nature photography, as well as in undercover or spy work. For instance, a photographer on safari will want to use a zoom lens to snap shots of a lion feeding. Another photographer may also use a zoom lens to capture shots of racecars driving or of the president and his entourage. In each of these examples, because the photographer can’t get close to his subject, a zoom lens is necessary to clearly capturing the image.

Digital SLR Cameras

SLR, which stands for single-lens reflex, refers to a type of camera that employs a rotating mirror (either a pentaprism or a pentamirror) that reflects the image that comes through the lens onto a focusing screen. From the mirror’s reflection, the images then appears in the camera’s eyepiece. The image only reaches the film after the focal plane shutter opens (when the photographer takes the shot).

Produced in 1935, the GOMZ sport was first version of the SLR camera to be made. Different models flourished throughout the WWII era that included improvements in the viewfinder’s orientation and the camera’s internal mirrors. Since the 1970s, amateur and professional photographers alike have been using SLR cameras.

Over the years as photographic technology improved, retailers produced SLR cameras that were equipped with LCD screens, improved lenses and microcomputers. Today, camera manufacturers such as Canon and Nikon have made digital SLR cameras available.

While digital SLR cameras give the photographer the advantage of viewing the scene without parallax distortion (apparent movement of fixed objects when the photographer changes position), they do prevent the photographer from seeing his shot at the moment the picture is taken.

Choosing Camera Lenses

Choosing camera lenses demands both knowledge of and experience with different types of camera lenses. Although knowing which lenses work best in given conditions is important, a photographer also chooses a particular lens to produce a specific photographic effect. Light, composition and subject matter of a scene all influence photographers’ choices of lenses.
Wide-Angle LensAlthough some will take landscape shots with telephoto lenses, most photographers opt for the wide-angle lens. Because a wide-angle lens has a wider field of vision than the human eye, it can take in more of a topographical expanse. Consequently, the wide-angle lens is one of the preferred landscape camera lenses.
A wide-angle lens can focus on the foreground and background simultaneously, another ability that the human eye lacks. Wide-angle camera lenses are best for large, dynamic landscapes where background and foreground both catch the eye’s attention. However, a photographer should refrain from using a wide-angle lens if he wants to focus in on the details of a single, distinct subject.
Zoom LensA zoom lens allows the photographer to widen or shorten the lens’ focal length to increase or decrease the magnification of the subject. This feature makes the zoom lens a popular camera accessory in many types of photography, ranging from landscape to portrait photography. However, because zoom lenses have small apertures (or lens openings), they are not well suited to taking pictures in low-light conditions.
Zoom lenses have replaced the fixed focal length camera lens in most camera models, especially with the advent of digital cameras. When choosing camera lenses, bear in mind that an optical zoom lens and a digital zoom lens are different.
While an optical zoom lens magnifies the image, a digital zoom lens crops the image after the maximum zoom is reached. Essentially a digital zoom enlarges and crops the image seen in the viewfinder instead of magnifying the subject. This digital enlargement results in lower resolution and, therefore, a poorer quality image.
When choosing camera lenses with zoom capabilities, photographers should look for high optical zoom capabilities rather than being deceived by claims about digital zoom capability. Pictures are of much better quality with an optical zoom lens.
Telephoto LensThe difference between a zoom lens and a telephoto lens is subtle. A zoom lens enlarges and magnifies the image. In contrast, a telephoto lens brings the subject “closer” to the photographer, reducing the distance between objects in the photograph and the camera’s lens. This allows a telephoto lens to show greater detail than the human eye could see at the same distance.
Fixed-Focal Length Camera LensA fixed-focal length camera lens is a permanent, non-adjustable lens found on some low to mid-range quality cameras. Often (but not always) doubling as a wide-angle lens, fixed-focal lenses tend to work well for low-light photos.
A fixed-focal length lens can do wonders for beginning photographers by helping them learn the art of photography. Without zoom capabilities, the photographer must give more thought to basic photography composition to produce good quality shots. Consequently, a budding photographer may learn the basics of good photography faster if by choosing a fixed-focal length lens.
Fixed-focal length camera lenses are less common than they once were, in part because most mid-range digital cameras now have built-in zoom lenses.
The Macro LensA macro lens is used to take extreme close ups of objects. Its short focal length allows the photographer to take pictures at close distances without distortions. The resulting image is as large as, or larger, than the original subject.
Choosing a macro lens has been complicated by digital camera settings. Originally, a macro lens was an extension tube for the camera lens. However, today’s digital cameras often have a macro setting. Although the setting replaces the traditional lens, it stillproduces the same effect as the previous macro lenses.
Macro lenses or macro settings are best used for magnifying the details of already smallobjects. For example, a photographer can use his macro setting to photograph ripples in water, the dew on a flower petal or the crevices of a rock.
Fisheye LensFisheye camera lenses distort the subject image, producing photos with curved and convex appearances. The fisheye lens was first developed for astronomy photography that seeks to capture as wide a range of sky as possible.
Today, the fisheye lens has become popular with landscape photographers, as the lens distortion curves horizons and hints at the earth’s curve. A portrait of a person taken with a fisheye lens has the distortion similar to what’s seen when looking through a door’speephole.
Front of Lens AccessoriesChoosing among different camera lenses isn’t an issue for most mid-range cameras because they already have built-in lenses that cannot be changed. While single lens reflex (SLR) cameras have interchangeable lenses, their steeper prices tend to make them a tool for professionals or serious amateur photographers.
For the hobbyist who doesn’t have an SLR camera, front of lens accessories that mimic the effects of certain lenses are available. A front of lens accessory is a disc that clips onto the front of a camera lens to provide specific effects. While some front of lens accessories filter out light, others mimic the effect of a wide-angle or fisheye lens.
Photos taken with a lens clip on accessory lack the quality of those taken with camera lenses designed for the same effect. As choosing a lens is not possible with many cameras, front of lens accessories increase the average photographer’s options.

Infrared Characteristics

Infrared radiation has a longer wavelength (lower frequency) and lower energy than light from the visual spectrum. The spectral range from 700 to 1350 nanometers can be photographed but conventional cameras are limited to the range of approximately 700 to 925 nanometers. Infrared beyond the 1350 nanometer range can be imaged but only with special non-photographic equipment. Georg Dittie's Thermal Infrared & Thermography web page is a useful introduction to imaging in the infrared region beyond the grasp of conventional photography. The infrared region between 1000 to 1350 nanometers requires special photographic equipment and special order film. Infrared spectrum in the range from 700 to 925 is the region that is most accessible to conventional photography.
Most 35mm, 120 (6cm)and sheet film cameras can be used for infrared photography in the range of spectrum from 700 to 925 nanometers. A few of the newer plastic body cameras may not be completely opaque to infrared.
You can easily test your equipment to see if it is completely suitable for infrared photography. Load a roll of infrared film into the camera and fire off several exposures at high shutter speed and small f-stop, with lens cap in place and indoors. If you open the fresh film container and load the film into the camera in total darkness you will have a completely unfogged roll making the test results easier to interpret. This will leave blank, unfogged film in the exposure chamber of the camera. Now place the camera in full 10 am to 2 pm April to September sunlight in several orientations for about 20 minutes in each (lens cap on if it is a rangefinder!). Process the film to normal or slightly greater than normal gamma. If the film is fogged, the equipment is leaking infrared radiation. Inexpensive, older model 35mm cameras usually make good infrared cameras if your plastic camera body leaks infrared.
The same test works for sheet film cameras and film holders. Sheet film holders are particularly troublesome with infrared photography and should be kept in the dark as much as possible. Some film holder bodies and dark slides may not be opaque to infrared. The dark slide, light trap may also leak infrared. Some view camera bellows may leak infrared. The safest solution is to keep direct sun off of the camera and film holders.
Since the range of infrared spectrum beyond 1350 nanometers is thermal radiation and imaging here involves recording heat patterns, infrared film tends to be especially sensitive to heat and age fogging. The further the film's sensitivity extends into the infrared region, the more apt it is to fog easily. Store infrared film in a cool place and shoot fresh film whenever possible. Process infrared film as soon after it is exposed as possible to minimize subsequent fogging.
Most photographic lenses are designed so that they have the same focal length for all colors of the visual spectrum. They are not usually designed to correct focus for infrared light. On many lenses there will be a red line or dot near the focus index. This is the correction factor for infrared. You focus visually, then move whatever is opposite the focus index to the infrared mark. This adjusts the lens away from the film by about 1/400th of the focal length (1/4 percent) and brings the infrared image into sharp focus at the film plane.
Most infrared films are sensitive to light from the visual spectrum in addition to infrared radiation. Various sharp cutting color filters can be used to limit imaging radiation to the infrared region. The following table gives mid and maximum usefully recordable wavelengths for several commonly available infrared films.

Sports Photography

We have all at one time or another been captivated by sports images. It may be Kirk Gibson's World Series Homerun, and the image of him running the bases, overcoming the pain he was in or an image of high flying Michael Jordan slam dunking a basketball with his tongue out. We have all been captured in the moment of human drama. We all like a good action photo and, in particular, if your kids play sports, you want to remember them in their toils.
Quality sports shots are somewhat difficult to come by. Most people have limited access to events to photograph them. The further away you are from the event, the harder it becomes to capture the event in a pleasing manner. Sports are an event where crowd control is important, not only for the crowd's safety, but for the players also. There is nothing more frightening than to be on the sidelines of a football game, focused on a play in the field, when out of the blue a 250 pound line backer drives a player into your legs or a foul ball comes crashing at your $8,000 lens!
Location, Location, Location!
You can only photograph things you can see. The closer you are to someone, the better you can see them. Sports are no different. You have to get as close to what you are shooting as you can. Typically, for a photographer with a press pass, you can get to the sidelines or other similar locations. You generally will not be permitted on the playing field. Depending on the sport, you most likely will be limited to designated locations. For instance, at most Division I football games, the media cannot shoot between the two 35 yard markers. For most people, the situation is even worse. You probably don't have press access and are stuck in the stands for your shots. Get as close a possible. Even if you make it to the sidelines, you will be jostling for space with many other photographers, both still and video who have worked hard to get there and have the same job to do that you have.
You also have to be familiar with the sport to be able to capture the moment. This means knowing where to position yourself for the best action. This is critical because of angular momentum that will be discussed in the section on freezing action. Not only does it matter with the subject, but the background. Look at what is going to be behind your subject. While we will try to minimize the impact that a background has, it will still be unavoidable. So you need to position your self where the background is the most pleasing.
The Decisive Moment
Sports and Action photography is all about timing. Its about reacting. Its about being in the right place at the right time and its about execute. These are all qualities of the athlete and those of the photographer as well. Each sport has predictable and unpredictable moments. Under "Knowing your Sport", you will learn about these moments for individual sports. For instance, in basketball, you will have opportunities to photograph layups, jump shots, free throws, etc. Understanding the timing of these predictable actions allows you to capture the peak moment, when the action is most dramatic.
By knowing these moments you can anticipate the action. This helps in two ways, one it helps you with focus which will be discussed in a later segment, and secondly it helps you snap the shutter at the right time. The saying goes "If you see the action you missed it." This basically means if you wait for the soccer player to head the ball then press the shutter release, the ball most likely will be sailing out of the frame. You have to push the button before the action so that the mirror has time to flip out of the way and the shutter open and close. There is a delay between the image hitting your optical nerve and the shutter closing. You have to, through experience, learn what that time is and adjust for it.
Required Equipment
Most sports are shot on 35mm cameras because of their portability. While some photographers have captured great sports moments with other format cameras, we will concentrate our efforts on the 35mm arena which is the most commonly used gear.
"Its not the equipment but the photographer who makes the picture" is generally a true statement. However with sports and action photography, having the wrong equipment means not getting the shots you want or need. This relates back to the section on location. The further away, the longer the lens is needed to capture the same image in the frame. Different sports require different lens lengths. For instance, basketball is generally shot from the baseline or sideline near the baseline. You generally can get good results with an 85mm lens in this situation. However, by the time the players are at mid court, you need a 135mm to capture them. If they are playing under the far goal, a 200-300mm lens is needed to fill the frame well, yet for shooting a soccer game, a 300-400mm lens is needed for just about anything useful.
Generally, for a 35mm camera, each 100mm in lens focal length gets you about 10 yards (9 meters) in coverage. This coverage means that on a vertical format photo, a normal human will fill the frame fairly well. Thus, if you are shooting American Football from the 30 yard line with a 300mm lens, you will be able to get tight shots in an arc from the goal line to mid-field to the other 40 yard marker. As players get closer, your lens may be too long. Many photographers will carry two bodies with two different length lenses for this reason.
Lens speed is also a critical factor. The faster the lens, the faster the shutter speed you can use, which as the lens grows longer, this becomes even more important. This will be covered in the freezing action section in more depth. If you look at the sidelines of any Division 1 college football game or an NFL football game, you will see people with really big lenses. These range from 300mm to 600mm or longer and even then, they may have a 1.4X converter or 2X converter on. You need fast shutter speeds to freeze action with long lenses. Every F Stop you give up requires a faster film or less freezing potential.
Most consumer grade long lenses and zooms have variable apertures, but most are F5.6 at the long end of the lens. F5.6 is good for outdoor day time shots, but becomes very inhibiting for night games and indoor action. Most people use lenses that are F2.8 or faster. These lenses are very expensive. A 400mm F2.8 sells for over $8000 US. They are also very heavy and bulky. Using a monopod is a life saver with these big lenses.