Why you should think beyond the kit lens that came along with your camera body ?
Unless you happened to purchase a compact 12mm-to-400mm f/1.4 zoom lens with your dSLR (they don’t exist), you’re deluding yourself if you think you can’t use an add on lens to improve your photography options and skills. Lenses don’t turn you into a better photographer, of course, but they do increase your opportunities and let you take pictures that you simply can’t grab with the lens that came with your camera.
The following sections list some of the things that an additional lens can help you achieve.
Shooting in low light
The do-everything zoom lenses furnished with dSLRs often have maximum apertures of f/3.5 to f/4.5. The very entry-level Nikon, Sony or Canon models are all accompanied in the kit form with 18mm-to-55mm f/3.5-to-f/5.6 zoom lenses.
You can’t compare the focal-length ranges directly, of course, because these popularly priced dSLRs have different crop factors, ranging from 1.5X (for Nikon, Sony, and Pentax) to 2X (for the Olympus line). But you can compare maximum apertures, and f/3.5 or slower is common among every manufacturer’s amateur / beginner lenses.
Although zooms that have large maximum apertures are expensive (and for a zoom lens, f/2.8 is a large maximum aperture), you can find fast fixed focal length Prime or Block lenses that cost very little. For example, a 50mm f/1.8 lens from a major camera manufacturer may cost less than INR 5000 or USD 100, even though it’s two f-stops faster than an f/3.5 lens and three stops better than an f/4.5 optic.
If you’re willing to spend a little more, you can buy 28mm, 35mm, 50mm, or 85mm f/1.4 lenses from the main camera manufacturing companies or fast third-party lenses, such as the Sigma 30mm f/1.4 or Sigma 20mm f/1.8. Those extra notches on the aperture ring let you take hand-held pictures in dark low light situations handheld especially when the camera or lens uses image stabilization or even otherwise sometimes without having to increase the ISO, which adversely effects the image quality. An indoor concert that calls for a 1/15-second exposure at f/4 and ISO 100 may work just fine at 1/125 of a second at f/1.4.
The fastest lenses are generally designed to produce excellent results even when wide open, so you needn’t fear using f/1.4 with a prime lens, even though you get relatively inferior results with your cheap zoom at f/4.5 However, just be careful to focus well and at the right place.
Improving your shutter speed
That wide aperture also pays dividends in the shutter-speed department. The difference between f/1.4 at 1/125 of a second and 1/15 of a second at f/4 can be quite dramatic from a sharpness perspective. You can find out more about making the most of slow shutter speeds by using image stabilization technology.
Producing sharp images
You may be able to get sharper images by adding better lenses, too. That does not mean that the lens you purchased with your camera is unsharp. However, your all in one kit lens is generally built on a foundation of compromises that may not necessarily produce the optimum results at all zoom positions or at all apertures. Other lenses that you add to your collection may provide better results at specific focal lengths or f-stops and even overall performance is much better. Go for the Canon " L " series lenses known for their superior performance. All brands have their superior range of lenses and it certainly is worth spending money on them as it is eventually the lens that decides the overall quality of an image.
A 200 mm f/2.8 is an excellent prime and a much more value for money if you do not need the flexibility of 70-200 f/2.8 zoom and if you generally shoot at 200mm. This is lighter both on the pocket and in weight with no compromise on quality.
Also that 50mm f/1.8 lens that you pick up for less than a 100 USD, just might be the sharpest lens you own. Spend a little bit more and you may go for the f/1.4 version with still better optics and build. Maybe your work does not require you to spend still a lot more and go for the f1.2 version. But if your photography involves a 50mm most of the time, you may consider it as a good investment.
A kit lens may also have "macro" mentioned over it but it may be just a gimmick and not truly a macro lens. You may opt to buy a close-up lens that’s optimized for macro photography and produces especially sharp images at distances of a few inches or so. These lenses are manufactured and dedicated for this purpose.
Your current lens is probably very good, but that doesn’t mean you can’t get sharper pictures with another set of optics, particularly when you’re swap- ping a general-purpose zoom lens for a fixed focal length prime lens designed for exactly the kind of photo project that you’re working on at the moment.
Taking a step back to the wide angle of view
Wide-angle lenses let you take in a wide field of view — in effect, stepping back from your subject, even in situations where you really don’t have room to move farther away. The lens that you bought with your camera likely provides a field of view no wider than that of a 28mm lens on a full-frame film SLR, which really isn’t very wide. You can get some very interesting perspectives by using ultra-wide lenses, including the 10.5mm fish-eye view provided by one Nikkor lens, particularly because Nikon offers a utility that can de fish the curved image to produce a more rectilinear (straight line) version. Your particular dSLR may have wide angles available with the equivalent of a super wide 18mm lens or better. Third-party vendors also offer some interesting wide-angle choices, such as the Sigma 10mm-to-20mm f/4-to-f/5.6 optic that offers the equivalent of a 15mm-to-30mm zoom on a dSLR that has a 1.5X crop factor. I’ve had a great deal of fun with a Tokina fish- eye zoom lens (used for Figure 6-2), which allows you to choose your degree of distortion over a 10mm-to-17mm range.
If you’ve been lusting after longer and longer lenses and thats exactly the case with the starters even if they don't shoot wildlife or sports, You are missing out on something if you have not explored the wide or an extreme wide angle of view. Its a whole new world when you explore with a fisheye or a 14mm lens on a full frame body.
The inverse of a wide-angle lens is the telephoto lens, and the telephoto lens’s long focal lengths let you bring distant objects much closer to your camera. The lens that came with your camera probably provides only a moderate telephoto effect, perhaps around 70mm, which with a 1.5 crop factor, is the equivalent of a 105mm short tele-lens on a full-frame 35mm film camera.
You can easily find long lenses, and they usually don’t cost much, simply because telephoto prime lenses and telephoto zooms are generally simpler to design than their tricky wide-angle counterparts. You can find 70mm-to-300mm zooms for many dSLRs for only a few hundred dollars. You can find prime lenses for even less. I picked up an ancient non- automatic (focus, exposure, and aperture) 400mm lens for about $79 that I use for great wildlife shooting, as shown in Figure 6-3, especially if I can mount the camera or lens on a tripod.
Your optional lens may be able to focus much more closely than the lens that came with your camera, making it a macro lens. If you’re new to close-up photography, you’ll soon find that the magnification of the image is more important than the close-focusing distance.
You can get the same size image with a 200mm lens at 8 inches as you get with a 50mm lens at 2 inches, and you may even be better off with the 200mm lens. The closer you get, the harder it may be to get good lighting on your subject. You simply don’t have a lot of room to apply effective lighting when you have a gap of only a couple inches between the front of the lens and that tree frog you’re snapping. Worse, the tree frog may get skittish at the proximity of your camera and you, making that 200mm lens and the extra distance it provides an even better idea.
So, you may add a fast prime to 1. Shoot at opened apertures to get nice shallow depth of field. 2. To be able to get higher shutter speeds and shoot hand held in low light situations. 3. Avoid the use of higher ISO. 4. Better overall quality 5. Light weight