Selecting a useful range of lenses for a manual focus 35mm SLR camera
May 16 '01
The Bottom Line First, cover the range you need, then cover the range you'd like to have; but don't waste money on paperweights!
It's quite common for a photographer to accumulate an impressive set of lenses, only to find that most of them stay on the shelf or in the camera bag. Being prudent in your choice of lenses is important, for the sake of both your bank account and your peace of mind. Lens selection should be based on requirements for utility, performance and cost. These requirements will dictate, to varying degrees, your selection of lens type (macro, fixed, zoom), focal length, maximum aperture, optical quality, build quality, size, weight, price and, sometimes, manufacturer.
The best place to start when building a lens line-up for a 35mm SLR system, unless you have special interests like wildlife or macro photography, is probably in the ‘medium’ range of focal lengths: approximately 28mm to 200mm. Lenses in this range not only meet 95% or more of most people’s needs, they also happen to be the least expensive. You can cover this range comprehensively with a pair of zoom lenses, such as a 28-70 and a 70-210; even one 28-210 zoom lens is possible but distortion is a real danger with lenses of such a wide zoom range. Alternatively, you may be better off with lenses of fixed focal length, either instead of or in addition to zooms. In any case, outside the medium range you are more likely to need fixed focal lengths.
This begs the question: "Why should I bother with fixed lenses when it would be more efficient and cost effective just to use zooms?" It's true that, when walking around with a camera, a zoom lens is very convenient. It's also true that a couple of zooms would normally cost and weigh less than half a dozen or more fixed lenses. Unfortunately, zooms involve compromise: they are generally slower (smaller maximum aperture), more prone to flare because of the large number of elements used, and introduce more distortion than fixed lenses.
A fixed lens may be called for if you need to take pictures in low light or with shallow depth of field, requiring a wider aperture than you can get from a zoom; or if you are taking pictures against the light and need to avoid flare; or if you need better resolution or lower distortion than the zoom can give.
Lenses for successful wildlife photography need to be of very long focal length, usually a minimum of 400mm, and exceptional optical quality; fixed lenses are the best choice. Macro photography also mandates the use of fixed lenses. Although some zooms offer a so-called 'macro' setting, they aren't satisfactory for serious macro work and they don't give enough magnification. True macro lenses are specially corrected for close focusing and have a flat image field. In fact, the excellent performance of some macro lenses makes them very good candidates for general use too. In serious architectural photography, wide angle perspective correction (PC) lenses are necessary to avoid converging verticals; these are always fixed focus lenses.
If you want to build a lens system consisting entirely of fixed lenses, consider carefully the range you need to cover and what would be sensible intervals between the focal lengths. A ‘comprehensive’ set of conventional fixed lenses for 35mm SLR photography could be 15mm, 21mm, 28mm, 50mm, 90mm, 200mm, 500mm; another possibility would be 18mm, 24mm, 35mm, 50mm, 90mm, 200mm, 500mm. You may want to throw in a macro or PC lens, too, depending on your requirements. But buy only the lenses you need; it's easy to get carried away and to buy exotic lenses that you'll rarely, if ever, use once the novelty wears off. Specialist macro lenses, PC lenses and lenses below 28mm and above 200mm in focal length are expensive.
Extenders (teleconverters) can add flexibility to your lens line-up; they are normally suitable only for use with longer focal lengths. For example, a 2x extender used with 90mm, 200mm and 500mm lenses would give focal lengths of 180mm, 400mm and 1000mm respectively, although you would lose 2 f-stops from the lens speed; so, for example, a 500mm f/5.6 lens would become a 1000mm f/11 lens. A 1.4x extender would offer less magnification but would cost only one f-stop in speed and might very well give better quality. Image quality is always compromised, to some degree, by the use of extenders and you should also be aware that not all lens/extender combinations are possible; physical damage can result from the incorrect application of extenders.
When it comes to selecting the maximum aperture at a particular focal length, most manufacturers offer several choices. For focal lengths in the 35mm to 75mm range, the widest aperture lens offered may be f/1.4, with other options at f/2 and f/2.8. The ‘faster’ the lens (i.e. the wider its maximum aperture), the more it will cost and the bigger it will be. It becomes exponentially more difficult to correct aberrations and distortions as the lens becomes wider. You should think carefully before making your selection: the more expensive option may not necessarily be the best for your purposes, even if you can afford it. In many cases, if you're not going to use the lens much wider than f/4, it won't make any difference in image quality which lens you use. It is true, however, that accurate focusing is easier with wider aperture lenses, especially in low light.
Some modern lenses are described as ‘APO’ (short for apochromatic), which means they have been corrected so that light at three different wavelengths is brought to the same point of focus, instead of only two wavelengths in the more usual achromatic lenses. APO lenses do a wonderful job of minimizing chromatic distortion but, naturally, cost more.
Build quality of a lens is important, especially if you anticipate heavy use and/or unfavourable conditions, including changing lenses frequently. Some lenses nowadays use plastic for the barrel and, sometimes, even the lens mount. This makes them much lighter than, but not as strong as, a well-built lens with barrel and mount made of metal.
Some people like to economise by buying zoom or fixed lenses from the independent manufacturers. Many good lenses are marketed by Tamron, Tokina, Sigma, Vivitar and others, with mounts compatible with the major manufacturers' cameras. In some cases, however, they do not really match up to the standards of the camera manufacturers' own lenses. Just bear in mind that good, cheap lenses are as rare as hens' teeth!
Finally, a few words about buying used lenses. You can save a lot of money if you are careful but you could also end up with an expensive paperweight. Dents on the filter ring or lens barrel are a sign of rough usage or accidents and could portend serious internal problems. Check that the focus ring, aperture selector and zoom control move smoothly, without being too stiff or too loose. Look through the lens to see that the diaphragm opens and closes properly as you change the aperture setting. Check that the lens fits your camera mount and locks properly into place. Check that the levers/cams that act as the lens/camera interface are undamaged and that the proper linkage is achieved between camera and lens.
Lenses with scratches on the rear element should be avoided, as these will almost certainly degrade the image quality. Front element damage is not usually so bad, unless it is extreme. A small amount of debris inside the lens is also not a serious problem. Lenses "breathe" when focus or zoom controls are rotated and a small amount of dust is unavoidable.
The biggest enemy of lenses is fungus. It can usually be avoided if lenses are always kept in a clean and dry place but you can't be sure how a used lens has been stored. If you look through a lens with this problem, you can usually make out a whitish web-like growth spreading across the surface of one of the inner elements. Fungus destroys the coating and can even etch the surface of the glass itself. It cannot normally be cleaned satisfactorily, so any lens with visible signs of fungous growth should be avoided.
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