One of the worst things fledgling photographers can do is be penny wise and pound foolish in their equipment purchasing decisions. I would strongly advise you to always purchase name brand lenses. If you own a Canon digital single lens reflex body, buy Canon lenses. This holds especially true in the case of Nature Photography. The price difference between an off brand lens could be measured far more than dollars in a few years down the road if it costs you potential clients, time and money. There is nothing worse than reviewing older images only to find gaping holes in the quality of the images simply because you opted to save a few dollars on your lens purchase. Remember to opt for the best quality lens you can afford. This especially holds true for long telephoto lenses or long zoom lenses. You are far better of saving your pennies and buying quality in the long run. It’s kind of like the old story of the hare and the turtle. Remember if there is a substantial difference in the price between a brand name lens and the off brand lens, chances are you are not just paying for the name.
One should have an array of lenses in their camera bag that compliments their camera body. Try to avoid buying super long wide angle to telephoto zoom lenses that offers the coverage of three lenses in one. Your image quality can be seriously compromised, for instance a 28mm-70mm lens will offer far superior images than a 28mm-300mm lens. Although it may seem like a good idea you are taking from Peter to pay Paul by using a lens with such a wide zoom range. Be aware fixed focal length lenses traditionally outperform zoom lenses. If we look at a 28mm f 2.8 lens and compare it the 28mm-300mm zoom, the fixed 28mm lens will out perform the zoom at the 28mm focal length hands down. It’s simply a matter of physics and lens design. Keep in mind all lenses are made up of groups of glass or epoxy elements lined up together making the optical formula of that particular lens. As you zoon in and out the groups of elements move inside of the lens barrel giving you the zoom range or optical formula of the lens. Be aware even the material of the lens barrel can affect the quality of your images. How so? A metal barrel will keep all the optical elements in critical alignment as you zoom in or out far better than a plastic or polymer barrel.
Many have argued the advent of computer designed zoom lenses perform nearly as well as fixed lenses. In some cases this can be true however remember to compare apple to apples. A Canon 100mm-400mm zoom may perform as well as the fixed Canon 400mm 5.6 fixed lens. By the same token there is little cost difference between these two lenses. If you live in an area where you can rent lenses, I highly recommend you do so as opposed to making your decision based upon a review of a competitive lens in a photography magazine. Keep in mind photography magazines do not survive through readership dollars they survive on advertising dollars. Long or short focal length, you do get what you pay for when it comes to lenses. Should you always spend top dollar on your lenses? Not necessarily but keep in mind what your objective is. If you just want to capture moments and images for you to enjoy and share with friends and family then maybe not. For those of you have serious aspirations or intentions of using your images in a commercial or competitive venue then the answer may very well be yes.