The chances are that when you started using your first DSLR, you were astounded by the image quality. It was probably a quantum leap over your previous camera—a true night-and-day difference. Chances are also that the lens on your first DSLR was what is known as a kit lens. Kit lenses are typically standard zoom lenses. 18-55mm would be typical. If you bought a dual lens kit, you may have a 70-300 telephoto in the package too. Kit lenses are great for starting out. They introduce you to the versatility of an interchangeable lens system, allowing you to understand concepts such as depth of field and perspective. They are, however, usually cheaply made, often with fairly limited variable apertures. Some, though not all, have less-than-stellar image quality.
A kit lens will get you started but may restrict you later
A good lens is an investment worth making
As your experience in photography develops, you may find these limitations hampering your creativity, be it getting a nice shallow depth of field or shooting action in low light. Perhaps now is the time to invest in professional glass.
The first thing to say about buying professional-quality lenses is; look at them as an investment. Unlike camera bodies, which are often technologically obsolete after a couple of years, a good lens may last your entire photographic career (as long as the manufacturer maintains the lens mount). Pro lenses are not cheap, but if you average the price out over the lifetime of the lens, they are good value.
Bigger is better sometimes
Pro lens image quality advantage
So what are the differences that professional lenses bring you? First and foremost is image quality. Pro lenses use highly sophisticated combinations of lens elements to ensure that you are getting maximum image sharpness across the full range of apertures. They will also contain low-dispersion coatings to reduce external and internal flare, hence improving image contrast and color. In addition, the lens groupings are designed to drastically reduce distortion in the image, most commonly pincushion, barrel distortion, and chromatic aberration. Whilst most modern post-production software can correct this to a certain extent, it is still better to create the highest-quality image that you can.
Pro lens Aperture advantage
Another advantage of pro lenses is that they will have a wider maximum aperture, opening the doors to the use of creative depth of field and nice bokeh (that soft look in out-of-focus areas of shots with shallow depth of field). Professional zoom lenses will also have a constant aperture. For example, a 24-70mm will be f2.8 at 24mm and at 70mm. Cheaper lenses will generally have a variable aperture, meaning that at the telephoto end, the actual aperture could be 1-2 stops less than at the widest end. The difference between f2-2.8 and f4-5.6 can be quite significant creatively, especially on mid to long telephoto lenses.
Shallow depth of field is more achievable with good glass
Pro lens build quality advantage
Build quality is another factor when considering lenses. Cheaper kit lenses will often have plastic barrels and flimsy internal construction. If you are using your camera regularly, you may find the lens could start to stick when rotating the zoom or focus ring or, worse still, fall apart. A professional-quality lens will have a barrel that is made of metal, giving extra strength, and the internal mechanisms will be better-designed, and of more durable materials. This will be noticeable in the fluid, almost dampened movement of the zoom and focus rings.
Kit lenses are less rugged than pro lenses
One area not often talked about with lenses is weatherproofing. Ads for professional cameras often talk about the number of seals that they have to protect the internals. Well, professional lenses are much the same, giving significantly better resistance to rain and—perhaps more importantly—dust. Dust can be a nightmare with cheap lenses, often working its way into the helical screw that controls the focus or zoom and completely jamming it. This issue is greatly reduced with quality lenses, as is the possibility of mould growing inside the camera elements, a problem common in tropical areas where the warm moist air can get inside the lens elements.
As we have said, professional lenses are not cheap, and to be honest, if you are an occasional shooter, probably not necessary. However, if you are stepping up to a new level in photography, you may soon find that your kit lens is holding back both your creativity and image quality. Then it is time to start looking at investing in high-quality lenses. Take your time and try different lenses on your camera. Third-party companies such as Sigma and Tamron can produce lenses at the same level as the camera manufacturers’ own lenses. Find what feels best on your camera and what gives you the image quality you are looking for. A professional lens will not make you a professional photographer, but it will give you a better chance of creating professional-looking images.