Z Is For Zoom

How Far Do You Want to Go?

Image #1. Focal length 18mm. Photographs copyright: DAVID McMAHON

This series of three photographs was shot on a dull, grey day – simply to illustrate the distinction between a standard lens and a zoom lens. Yes, I could have done the same experiment on a cloudless, sunny day, but the tougher the light conditions, the greater the demands on your lens.

Until about three or four years ago, zoom lenses were the exclusive territory of professional photographers. Amateurs who bought SLR (single-lens reflex) cameras generally bought standard 35mm lenses. But as digital SLRs grew in popularity and the prices fell from around $3000 to the $1200 mark, it became more common for amateur photographers to turn to single compact lenses with adjustable focal planes.

Then came the biggest – and most far-reaching - revolution for the MND (mum ‘n’ dad) photographers. As they embraced digital SLRs and the price of memory cards fell from $200 for a one-gigabyte SD card (late 1995) to $30 for a four-gigabyte SD card, a new school of thought took hold.

As the MND amateurs began looking for more than simply a standard 35mm lens, manufacturers found a new market – complete amateurs who were willing to spend some money on the popular 18-55mm lenses or even the larger multi-purpose 18-125mm lenses.

Logically, the camera manufacturers embraced the new market. It’s been more than a year since the big names started to package novel deals for the home photographer, as opposed to serving only the professional photographers.

Image #2. Focal length 125mm.

Previously, when an MND photographer bought a digital SLR, it came with one lens. Now, Canon, Nikon, Pentax and the other big players are enticing brave new consumers to invest in packages that are tailored to the one-body-two-lenses option.

If that sounds like jargon, let me explain it in the simplest terms. You buy one camera body, but the manufacturer entices you (and a brilliant marketing option it is, from everyone’s point of view) to buy not one lens but two.

Each camera body has a bayonet-type screw-in for a lens. If your standard lens is an 18-55mm lens, you can also buy a second, longer lens and swap between the two. Swapping lenses is a quick and simple process that only takes a few seconds. More crucially, it makes a lot of commercial sense for manufacturers and for the 21st-century buyer as well.

When I bought my Pentax K100D, I bought a wonderful 18-125mm Sigma lens. Then, about eight or nine months ago, I saw a 70-300mm Sigma lens advertised and after mulling over the possibilities for a few weeks, I took the plunge and have never looked back. I carry both lenses wherever I go and to put it quite simply, I revel in the choice.

Now to the specifics of this photo exercise. All these shots were taken from the eleventh floor of a city building here in Melbourne, looking out towards Port Phillip Bay. All three shots were taken from exactly the same spot, with different focal lengths.

In the first shot, with a focal length of only 18mm, the dominant features are two apartment buildings, a set of vertical blinds and an old-fashioned CRT-type computer monitor.

The second shot is also taken with my 18-125mm lens, fully open to a focal length of 125mm. Now you can actually see what looks like an expanse of concrete in the distance but is actually the sea under a leaden, grey sky.

Image #3. Focal length 300mm.

In the final shot (above) taken at the maximum focal length of my 70-300mm lens, you can actually begin to discern the slim grey outline of a container ship several miles away, deep in the Bay.

It’s almost like sittin’ on the dock of the Bay.

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