Ever looked at the photographers at a major sports event? Most commonly you will see a barrage of massive lenses, often 300-600mm in focal length and with massive front elements. The photographer at a wedding may have a 24-70 f2.8 and a 70-200 f2.8 lens, again both much bigger than the lenses found on most enthusiasts' cameras. So why have these lenses and what are the pros and cons?
Lets start with the Pros. The reason that these lenses have such large front elements is simple, to let more light in. The wider the aperture the less likely you will need to use a high ISO with its potential degradation of the image.
Another effect of the wide aperture is to allow the photographer to create images with a shallower depth of field.
Professional level lenses will also use higher quality glass, usually with more of the special surface coatings that reduce both flare and internal reflections. Nikon use Nano coating, this is covers the rear element of the lens reducing flare caused by reflections from the sensor itself. All of these surface coatings lead to higher image contrast and better colour.
As well as using higher quality glass, pro lenses will have more complicated and tightly designed lens elements. Elements are the groups of different lenses within the lens. One of the effects of these elements is to reduce distortion such as pin cushioning, and barrel distortion. This distortions most often manifest themselves as curvature in images with straight lines.
Professional lenses are usually much sturdier than lower cost equivalents. The barrels are often made from metals rather than plastics and they are also weather sealed, providing protection against the elements. I recently had the misfortune of having a Nikon 24-70 drop onto a concrete floor, the metal barrel protected the elements and as such it could be repaired back to A1 condition.
Finally, with the increasing number of megapixels in modern cameras, low cost lenses are not going to keep up with sensor resolution, whereas a good quality pro lens should.
The most obvious of the cons is cost. Professional lenses will often cost two to three times more than their cheaper equivalents, so replacing your entire lens set up for professional glass is going to take some investment. That said, lens technology does not advance anywhere near as quickly as sensor technology and investment in professional lenses should last you literally decades. If you do decide to go pro, think about whether you will want to go full frame in the future, there is no point in investing in a good range of APS-C glass only to find it will not work on your new full frame camera in the future.
Another consideration is the weight. Pro lens weight is often double if not triple normal lenses. Pack two or three of these in your kit bag and you will certainly know that you have been carrying them by the end of the day. On smaller cameras they can also upset the overall balance of the camera.
Lastly, because they are so big, they mark you out as a photographer. The effects of this can range from the minor, strangers constantly asking you to take their pictures with their camera to the ugly, being marked for a potential theft. When using a pro lens, try to keep it out of sight when not in use, to avoid unwanted attention.
So do you need a pro lens? Well only you can answer that question. Hopefully this article has gone some way towards helping you make your mind up.
Jason Row is a British born travel photographer now living in Ukraine. You can follow him on Facebook or visit his site, The Odessa Files. He also maintains a blog chronicling his exploits as an Expat in the former Soviet Union