PHOTOGRAPHY ACCESSORY ADVICE

The Photography Resource
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Tips on Photography Accessories
Lenses Lenses and Creative Vision Zoom Lenses Polarizing Filters
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Lenses
Lenses are the eyes of your camera, you can change the way your camera sees things simply by changing lenses or by changing your zoom settings. Matching the right lens to the right subject is one of the keys to creative photography. Knowing which lens or zoom setting to use is largely a matter of what end result you are looking to achieve, combined with your understanding of the basic characteristics of different types of lenses.
All lenses are described by focal length, measured in millimeters and by speed (maximum aperture size) ie. A 300mm f/2.8 lens has a focal length of 300mm and a speed of f/2.8. The focal length of a lens is important as it gives you an idea of how its angle-of-view and perspective relate to our own vision of the world. Lenses of around 50mm are considered normal because they provide approximately the same perspective that our eyes see. Lenses shorter than 50mm are classed as wide-angle lenses and longer lenses with a greater focal length are considered telephoto lenses.

You should be aware that lenses for digital cameras are often referred to in their '35mm' counterparts' focal lengths rather than their actual physical focal lengths. This is because manufacturers are aware that most photographers used the focal lengths of lenses for 35mm cameras as their point of reference. Also, because the size of the sensor in different digital cameras affects the actual focal length, and because sensor size varies in DSLR's, it is simpler to use lenses for 35mm cameras as a standard. For these reasons, you will often see the 4X zoom range of a digital point-and-shoot camera referred to as '35-140mm' rather than its actual focal length.
If you own a DSLR camera, it may incorporate what's known as a 'cropping factor' in determining the 'real' focal length. Because the sensor in many digital cameras is smaller than a 35mm frame of film, the 'working' focal length of any lens used on that camera increases. If your camera has a cropping factor of 1.5X, for example, the working focal length of that lens is 1.5X its stated size. In other words, if you were using a 100mm lens from a 35mm camera on your DSLR body, and the camera had a cropping factor of 1.5X, the actual working focal length would be 150mm. Your manual will explain this in greater detail but it is worth being aware of this especially when buying second hand lenses where you may not be offered the professional advice you would get in a camera store.
Lens speed indicates how bright the image in the viewfinder will be. Lenses with larger maximum apertures provide a brighter viewfinder image but are not necessarily sharper or better than slower lenses. The main advantage of faster lenses is that they provide better viewing in poorly lit situations. For example, a 200mm f/2.8 lens (considered very fast for a lens that long) would produce a brighter viewing image than a 200mm f/5.6 lens. General rule of thumb is that lenses with wider maximum apertures are more expensive.
Lenses and Creative Vision
Lenses have traditionally been divided into three basic categories: normal, wide angle, and telephoto.
Normal lenses provide about the same perspective as the human eye and usually have a focal length of around 45mm to 60mm (35mm format equivalent). On most zoom cameras, the normal focal length is typically in the middle area of the zoom range. Normal lenses offer a straightforward view of the world that is well-suited to documentary-type images of subjects like architecture or landscapes.
Wide-angle lenses are best at reaching out their wide-open arms to take in a sweeping view of the world. Those in the 28mm-to-35mm range are the most useful and popular to achieve stunning panoramic landscape photos. Creatively, wide-angle lenses can be used to heighten perspective by exaggerating the distance between near and far objects or, when you're shooting upward, the height of nearby objects (exaggerating the height of a tree or a skyscraper for example). Wide-angle lenses are good for a range of subjects, including landscapes (especially where you want to elongate spatial relationships), architecture (when you want to create dramatic or distorted shots of exteriors), and in any situation where shooting space is tight. They also provide a much greater depth of field than other lenses.Telephoto lenses have focal lengths that range from about 85mm (perfect for portraits) to super-telephoto lenses of 300mm-600mm (the kind of lenses you see at a sports match or on wildlife programs). The aim of all telephoto lenses is to bring distant subjects closer, and the longer the focal length of the lens, the greater the magnification. Zoom Lenses
Zoom lenses have an adjustable focal length, and virtually all digital point-and-shoot cameras and full-featured zoom cameras come pre-fitted with a zoom lens. The biggest virtue of the zoom lens is that they let you widen-out or zoom-in on composition without having to change your shooting position. Zooming only changes the relative magnification; it has no effect on perspective or size relationships, so creatively it's often more effective to change perspective by changing your shooting position rather than relying solely on your lens.
Zoom lenses are described by their multiplication factor, 3X or 4X etc. What that number means is that the longest telephoto setting is three times or four times the focal length of the widest wide-angle setting. If you have a 35mm-105mm zoom, then that lens will have a 3X zoom range. Everything else being equal, the longer your zoom, the more flexibility you will have when creating compositions.
If you're using a DSLR camera, you can cover a wide range of focal lengths with just two or three zooms. By carrying a 24mm-105mm lens or a 70mm-300mm lens in your bag, you'll be covering everything from wide-angle to super-telephoto focal lengths with just two lenses.
Polarizing Filters
If you're using a digital SLR camera the single most useful accessory you can own is a polarizing filter. This seemingly simple filter which screws to the end of your lens, in a rotating mount, performs a host of fantastic photographic objectives including darkening blue skies, removing reflections, and increasing color saturation and contrast. To understand how it works would require a degree in the physics of light. But using one is quite simple. All you do is turn the filter until you see the effect you want in the viewfinder, and then shoot.
Polarizers are most commonly used to darken blue skies in outdoor and scenic photographs by slicing through haze in the atmosphere. Sky-darkening works only when the sun is at about 90 degrees from the angle you're facing; in other words, it must be to your left or right or overhead, but not behind or in front of you. Nor does the effect work on overcast days. It's best to use sky-darkening in moderation, too much saturation can make skies look very unnatural.
Polarizing filters are really handy for removing reflections from nonmetallic surfaces like water or glass. If you're trying to shoot a store-window display, or a fish in a pond, just turn the filter until the reflections vanish. The effect works best when you are at a 35-degree angle to the surface. You can even use a polarizer to remove the multitude of reflecting glares in outdoor scenes, making subjects like leaves and grass vibrant and rich with color.