Beginners guide to lenses

The fundamental advantage of an SLR (single lens reflex) camera over cameras of the point-and-shoot variety is the incredible variety of lenses available. From fisheyes to mega-telephotos, everything is covered - the only limit being your imagination (and wallet). This article is a brief overview of what's available and what to consider when decisions have to be made regarding purchasing and using lenses. Note: This article refers primarily to Nikon brand lenses (Nikkor) not for any other reason other than my familiarity with the system and the vast variety of models available. All information applies equally to any other brand of 35mm equipment whether it be Canon, Pentax, Minolta etc... The basic principles also apply to medium and large format equipment though focal lengths need to be converted to determine approximate focal length equivalents. As a rough guide multiply 35mm focal lengths by x2 for medium format, x3 for 4x5 inch format and x6 for 8x10.

The Basics

The focal length of a lens is measured in mm with the 'standard' lens for a 35mm camera being 50mm and having an angle of view of 45 degrees. Shorter lenses are referred to as 'wide angle' and have a wider angle of view, often 80 or 90 degrees. Lenses longer than 50mm are 'telephoto' with progressively narrower angles of view as the focal length increases. Zoom lenses can be of the telephoto or wide angle variety (or both) and have the added feature of being able to alter their focal length within a given range. Macro lenses allow close-up photos by extending the lens from the camera body further than usual.

For the beginner, a wide angle lens is used because it 'fits it all in' while telephoto lenses are used to 'get closer'. This is of course true, but as the focal length of the lens changes, other factors also come into play.

Perspective is enhanced with the use of wide angle lenses and compressed when shooting with telephoto lenses. This is often as much a reason for choosing a lens as its angle of view. A super-wide lens will dramatically increase the size of the subject in the foreground in relation to the background, making it the first choice of many landscape and newspaper photographers. On the other hand, a telephoto lens will 'pull together' the foreground and background which is useful when repetition needs to be shown (eg. street lamps in a row).

Depth of field is the area of sharp focus behind and in front of the subject you've focussed on. Primarily adjusted by varying the aperture which which the photograph is taken, it is also greatly affected by the choice of lens. A super-wide lens (such as a 20mm) will allow a depth of field from infinity to 1 foot at f22 while the depth of field with a telephoto lens (in this case a 180mm) is infinity to 80 feet! Depending on your subject, either lens can fulfil your needs - the telephoto separating the subject from the background and the wide angle, layering the subject upon the background.

To Zoom or not to Zoom...

Since the invention of zoom lenses thirty or so years ago, there are been constant arguments for and against their uses. In this time, zoom lenses have mostly replaced 'prime' lenses primarily for reasons of convenience and cost, but most purchasers are blissfully unaware of their pitfalls. There is no doubt that zoom lenses are convenient and versatile and if chosen carefully, will produce many beautiful images, but you should consider the following before parting with your hard cash...

Zoom lenses tend to be 'slower' than their non-zoom counterparts. This is a reference to the maximum aperture of the lens (eg. f5.6) which will affect ease of focussing, shooting in low-light etc...

Zoom lenses which offer a wide angle to telephoto range (eg. 28 - 200mm) often exhibit a multitude of optical problems including pincushion or barrel distortion (the titles are fairly descriptive of the effect) as well as loss of sharpness and illumination in the corners of the frame.

If you intend to buy a zoom lens, you're probably better off sticking to a name-brand (eg. Nikon, Canon etc...) good quality model which isn't too ambitious with it's range or features. A 20-1000mm zoom lens may sound inviting but would (if it existed) be quite horrible optically and probably weigh 20lb's as well! Stick to a tele-tele or wide-wide zoom lens and avoid lenses of the wide-tele variety as they tend to be pretty ordinary in term of optics!

Ultimately with all lenses, you get what you pay for, so don't expect miracles from a generic brand zoom which is offered to you when buying your new camera body. It'll probably be OK for small prints, but you'll certainly see the difference when you start to enlarge or shoot transparency film.

Fisheye lenses

16mm fisheye lens A fisheye lens is essentially a lens, so wide that it bends lines within the image to produce an overall curved image. A true fisheye lens 'sees' in 180 degrees, though more common today is a 'full-frame' fisheye (such as the Nikkor 16mm) which is 180 degrees across the diagonal corners of the frame. While the uses of these lenses are limited, they put a quirky perspective on life and capture images previously impossible with any other optic.

With recent innovations in design, excellent lenses are available starting at a focal length of 14mm. In layman's terms - if you used this lens standing in the corner of a room, you would see both walls on each side of the camera (as well as the entirety of the room). Recently much research has been put into the development of super-wide lenses for use on digital cameras (as a 14mm lens on a digital camera equals about 21mm on a 35mm camera) which is good for the rest of us as these lenses were previously completely out of reach and are now (almost) affordable.

Common wide angle focal lengths and their uses...

14mm - Tricky interior or special effects shots 20mm - Conventional super-wide perspective shots and cramped interiors 24mm - General purpose super-wide lens with little distortion 28mm - 'Safe' wide angle lens (group shots, architecture etc...) 35mm - 'Standard' wide angle lens - great for photo-documentary work Canon and Nikon have recently released 17-35mm zoom lenses - impressive optics with an equally impressive price tag! I personally prefer to carry a few prime wide lenses (20, 24 and 35mm) and work with one or another for a while, exploring the possibilities of each focal length before moving on. Zoom lenses can make you lazy - rather than moving to the ideal viewpoint, zooming to suit. While this may produce a similar image composition, the perspective and viewpoint may not be ideal (though your shoes will last longer).

A popular wide lens for the photo documentary photographer is the 35mm as it's slightly wider than standard allowing in a little of the environment, some perspective to make the shot interesting and a little more depth of field to make it all sharp. Have a look at the work of Henri-Cartier Bresson to see some good examples of this.

Standard Lenses

Largely replaced by the 35-70mm zoom lens (or equivalent), the 50mm standard lens provides the photographer with an angle of view similar to that of the human eye. It neither distorts nor enhances perspective, merely documenting whatever is in front of the lens. Some would say the focal length is photography at its most honest - you decide... The low distortion and flare characteristics of standard lenses make them ideal for copywork while their fast maximum aperture (often f1.4) helps when shooting anything in low-light. A more popular choice of lens is the standard macro (eg. Micro Nikkor 60mm f2.8) as its uses are supplemented with a close-up capability as well as exceptionally sharp optics.

Telephoto Lenses

Again, largely replaced by zoom lenses, the main reason to choose a fixed focal length telephoto is its maximum aperture. Most zoom telephoto lenses have a maximum aperture of f4.5 or f5.6 while many prime lenses are available in f2.8 which is up to 2 stops faster making it easier to focus and better in low-light. A faster maximum aperture also makes the background more out of focus - of particular concern to fashion, portrait and sport photographers. If you do end up purchasing a zoom telephoto lens, don't get too ambitious with the range (ie. 50-300mm won't be as good as an 80-200mm).

Common telephoto lenses and their applications...

85mm - Great for portraiture (not necessarily close-up though) 135mm - Close up head shots and a compact all purpose short-tele lens 200mm - Sporting events and enclosed wildlife photography 300mm - Distant wildlife and close-up sport 600mm - Native animals which don't really want to be photographed! The conventional view with portrait photography is in order to flatter the subject, a telephoto lens compresses the perspective slightly, thereby making the face look flatter (in particular the nose). This may be true in the case of close-up head shots (hence my 135mm lens recommendation), but you should experiment with a range of lenses depending on the style of portrait you're taking. A standard lens used horizontally will give some nice space either side of the head while a vertically used 28 or 24mm lens from above can make for some interesting environmental portraiture in the workplace.

Regardless of your typical photographic genre, every kit needs at least one telephoto lens and if that's the case, either a 135mm or 200mm will stretch to cover most bases.

Macro Lenses

Specialist macro lenses might seem indulgent and unnecessary at first but once you've used one, you'll realise a whole other world of photos out there waiting to be taken! Cheaper alternatives to a dedicated macro lens include close-up diopter filters and extension tubes. The former are easy and cheap but are less than ideal optically. Extension tubes simply increase the distance between the lens and the film plane, thereby creating greater magnification. For most subjects they're OK, but tubes come in limited sizes and quality is greatly dependent on the lens mounted being used.

Dedicated macro lenses will generally focus from infinity to 1:1 (life-size reproduction) in one sweep. They have the added advantage of being flat-field (a technical phrase for low-distortion) necessary for 1:1 copying of transparencies and other straight edged subjects such as stamps. If your passion is photographing insect or butterfly life, maybe look into a 105mm or 200mm macro lens as your 'working distance' will increase proportionally to the focal length, making stalking your prey all the easier. A greater working distance also makes lighting the subject easier as there's simply more room for a flash or reflector and less chance of the lens casting a shadow. A popular companion to the macro lens is a ring-flash, which as the name suggests, is shaped like a ring and mounts around the front of the lens to evenly light the subject. Recently these specialist flash units have become popular in fashion and portrait photography - but that's another story.

Specialist Lenses

MIRROR lenses are rarely seen these days, but were very popular in the 70's as an affordable option to long-telephoto lenses. Utilising a mirror system, they produced a long lens in a small package quite cheaply. The trade off was a set aperture (generally f8 or f11) and donut shaped highlights in the out of focus areas of every image. It was probably this highly recognisable feature that killed off professional use of this lens many years ago!

PC (or perspective control) lenses shift the lens in relation to the film plane (either across or at an angle to the camera) to either alter the image placement on the film or the perspective/focus within the image. They're a 35mm version of the features available on a large format view camera and have gained recent interest with the move toward 35mm digital cameras for product photography where altering the plane of focus is critical to the final image. For the regular user, they allow 'correct' architectural photos to be taken of buildings without climbing a ladder, by simply moving the lens up, thereby changing the perceived viewpoint without all the hassle. My advice - don't bother unless you have a specific task to accomplish - they're expensive and slow to use, and most clients prefer larger formats for architecture anyway.

Suggested Kits

Here are some of MY opinions on what to get depending on your needs and budget. The best thing is to buy lenses gradually as your photography grows. This way you'll get the most out of each lens and still get excited when you get a new one to play with!

The Photography Student. - 24mm wide, 60mm Macro, 135mm telephoto.

The Landscape Photographer. - 20mm super-wide, 35mm wide, 50mm standard, 135 or 200mm telephoto (for compressed shots).

The Sport Photographer. - 24mm wide (for groups and set-up shots), 80-200mm f2.8 zoom (yes, but it's a GOOD zoom lens), 300mm f4.5 (or f2.8 if you can afford it).

The Wedding Photographer. - 24mm wide, 50mm f1.4 standard (for low-light inside churches etc...), 85 or 135mm telephoto or 80-200mm f2.8 (depending on your budget and style of work).