There are two types of lenses available: Large aperture pro lenses and slower models aimed at amateurs. Pros prefer lenses with fast maximum apertures of f-2.8 or faster with exception of 500mm lenses and longer focal lengths which have a maximum aperture of f-4 or smaller. The main reason a pro needs an f-2.8 or faster lens is the extra stop of light which provides faster shutter speeds in low light. To a pro even one stop of faster shutter speed means getting a good shot which equals a sale, or missing the shot and going home empty handed. Pro lenses are also sharper at wide open apertures compared to amateur lenses. A 300mm f-2.8 is sharper wide open than a 75-300mm f-5.6 zoom set at 300mm and f-5.6. Pro lenses are also better built than amateur models. All metal lens bodies are required by pros who work under rough conditions and can't be too careful with their equipment. Amateurs usually don't need the extra protection for their lenses so manufacturers use less expensive materials to make lenses for amateurs to keep the cost down. The question many amateurs ask is whether or not they should spend extra money to buy pro lenses or stay with lower cost amateur lenses and still get good results.


Fast and shorter lenses in my opinion should be purchased only if you work in low light or need the brighter viewfinder for focusing which wider aperture lenses provide. Wide-angle and short telephotos are usually stopped down to gain more depth-of-field. This makes the lenses sharper so the sharpness between the pro and amateur models will not be as noticeable. You can purchase lower priced wide-angle and short telephotos and get quality results almost identical to those made with fast aperture pro lenses as long as you stop the lens down two or three stops and use a tripod. However, if you regularly work in low light or indoors such as indoor sports arenas, you should consider the pro versions. You should also consider a pro wide-angle or short telephoto if you work under rough conditions as pro lenses are built to withstand more abuse.



Above image was taken with a pro quality Tokina 20-35mm f-2.8 ATX lens.

Pro lenses have another advantage over amateur models. They provide constant aperture. A 28-70mm f-2.8 lens can be set to any length at f-2.8 while the f-stop on a 28-70mm f-3.5-4.5 changes as you zoom the lens. At 28mm you get a fast f-3.5 f-stop, but only f-4.5 once you zoom to 70mm. Why? the size and cost of a lens is directly related to its maximum aperture. Fast aperture lenses are more difficult to produce so they carry high price tags. The size of the lens gets bigger as the maximum aperture gets wider. The maximum aperture of any lens is the size of the diaphragm used wide open and is determined by dividing the focal length by diameter of aperture. A 100mm lens with a 50mm diameter has a wide aperture of f-2, 100 : 50 = 2. A 200mm lens with the same 50mm diameter has a wide aperture of f-4, 200 : 50 = 4. As you can see, lenses become bigger and heavier as the focal length gets longer and f-stops get faster which adds to their cost. Manufacturers produce variable aperture zooms for amateurs to keep the size and cost down.

Telephoto lenses with very fast apertures are much larger and heavier than shorter lenses. The cost of these fast teles are very high. A 300mm f-2.8 can cost well over $3000 dollars and a 400mm f-2.8 can cost $7000. This is beyond most amateur's and even pro's budgets. Wildlife and sports photographers or even fashion photographers invest in fast aperture telephotos simply because the need the extra speed to freeze action or make a blurred soft focus background for fashion photography. If you do telephotography and need fast shutter speeds in low light or need the sharpness you can get with these lenses for large reproductions, then invest in one of these fast optics if you can afford one. Fast telephotos also come in handy when working with teleconverters. Most manufacturers produce matched 1.4X and 2x teleconverters for their fast teles to produce maximum possible sharpness. Slower telephotos or zooms can be used with very good results if you use a tripod. With faster modern films you can shoot and freeze action without loosing sharpness. Faster teles will still produce sharper results wide open, but this becomes more apparent when making larger prints. If you can't afford a fast telephoto or you find them heavy to carry, try a fixed or zoom lens with smaller apertures. A 300mm f-4 or 400mm f-5.6 telephotos for example, are much smaller and more affordable than faster models and they produce quality results if used properly.

Above Image: Canon EOS A2, Tamron 200-400mm f-5.6,  Fuji Provia 100, 1/250 sec at f5.6. Spot metering on aperture priority. Bogen Tripod and ball head.

Owning a fast lens is nothing to brag about. Learning to use your equipment and good photographic technique is what makes good images. I own both fast and slow lenses and use them depending on the situation. I don't bother carrying my heavy 300mm f-2.8 when my smaller and lighter 400mm f-5.6 can give me the results I want. My advice: buy the best lens you can afford and learn to use them to their full potential. The best you can afford may not be the best there is, but with good photographic technique, your pictures can be.