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Point and Shoot #5 - What lens or focal length should I use

By: Miriam Arndt, Category: At The Museum, Date: 15 Mar 2012

From the blog series 'Point and Shoot' by Museum photographers Carl Bento and James King

What lens or focal length should I use?

The most important lens you have is your legs. The best wide-angle lens? Two steps backward. Look for the 'ah-ha'. – Ernst Haas

A photographer went to a socialite party in New York. As he entered the front door, the host said, 'I love your pictures – they're wonderful; you must have a fantastic camera.' He said nothing until dinner was finished, then: 'That was a wonderful dinner; you must have a terrific stove.' – Sam Haskins

For ease of explanation, all focal lengths mentioned below and relationships to angle of view, unless otherwise stated, refer to 35 mm film cameras and the full 35 mm digital image sensor format.

Choosing the right lens and what to carry in your kitbag depends on the subjects you want to shoot. Here are some examples:

• a photographer specialising in plants or insects would likely use a 60 mm or 105 mm macro lens. These are specially designed to focus at a much-reduced subject-to-lens distance than normal lenses.
• a wildlife photographer favours a large telephoto lens that allows them to capture animal behaviour in detail from a distance.
• a photographer walking the streets taking documentary-style images of people will choose a relatively wide-angled lens to capture a wider scene, which may help the story being told.

When it comes zoom and fixed-focus lenses, we are mainly concerned with DSLRs and compacts that may have inbuilt zoom functions or interchangeable lenses. When purchasing a new camera that has interchangeable lenses, a zoom lens is often bundled in the price. Although convenient and relatively inexpensive, these lenses are sometimes of questionable quality and you should not rely on them as your only lens.

Like most things, quality depends on price, and a good lens can cost thousands of dollars, particularly a good zoom lens. This has to do with the quality of build, glass and speed (meaning its light-gathering power). A large amount of glass at the front of a lens lets in more light and allows the photographer to catch the action at faster shutter speeds (very important for wildlife and sports photographers).

It is better to invest in a group of prime lenses with fixed focal lengths that offer the best image quality, such as:

• 35 mm or less – these offer a wide angle of view
• 50 mm – offering a standard or normal angle of view, these versatile, often-overlooked lenses are usually the fastest and sharpest in a photographer’s kit bag
• 85–105 mm – a slightly narrower angle of view, typically used for portraits
• 100–1000 mm – a much narrower angle of view which diminishes as the focal lengths increase (telephoto lenses).

Different-sized image sensor formats create a different focal length to angle-of-view relationship. For example in a DX format (2/3 that of a full 35 mm sensor), a standard lens producing a normal angle of view will be 35 mm in focal length, but in a small compact camera, the focal length will be around 10 mm. The focal lengths of lenses and their corresponding angles of view are always relative to the size of the image sensor.

Each manufacturer has their own set of prime lenses and, except wide-angle lenses, are reasonably affordable.

A good compromise for the non-professional is to carry two zooms: one that favours a variety of angles of view, from wide to just beyond normal (24–70 mm) and another that for just beyond normal to narrow (70–200 mm).

But the most important piece of advice I can give is to buy the most expensive lenses you can afford as these will most likely outlive the digital camera body you bought them for.