How to Choose a Camera Lens

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Don’t just take what they give you…

Need help with how to choose a camera lens? This article gives some tips that could easily stop you making an expensive mistake.

Before you buy your next Digital SLR camera consider the lens that ships with it. Often this will be a ‘normal’ or ‘standard’ lens – a widely used lens that reproduces with a magnification and perspective that matches how the human eye normally sees the world.

Could that be a waste of money? There is no point buying a normal lens with your camera if that lens is going to spend most of its time sitting in a case. Consider ordering your DSLR body without a lens and choosing a non-standard lens instead.

Different Cameras = a Different Normal Lens!

Twenty five years ago choosing a lens was pretty easy. They didn’t come with autofocus and, if you were buying for a 35mm SLR camera, you knew that any given focal length would provide the same magnification across all makes and models of camera.

Today things are different. With Digital SLR cameras having different image sensor sizes, a 16 mm lens for one model could produce a very different image to a 16 mm lens used on a different model (even if they share the same manufacturer).

The trouble is this – to produce a ‘normal’ view (ie the kind of view the human eye sees) a camera that’s used to take images that are normally viewed fairly close to the viewer should use a lens with a focal length of approximately the same length as the diagonal across the image sensor. Twenty five years ago almost all SLR cameras used full-frame 35mm film which was 24 × 36 mm. The diagonal was 43.3 mm and so 50 mm lenses were typical used as ‘normal’ lenses.

Today, due to the cost of making image sensors, many DSLR cameras use sensors that are smaller than 24 x 36 mm. So for each sensor size, the focal length of the normal lens is going to be different.

That also means that for a lens to be considered a telephoto lens, it’s focal length will vary according to the image size. Ditto for a wide angle lens.

Checking Your Focal Length

So the first thing you must do before buying a lens, especially if you are going to buy on-line without testing the lens first, is ensure you know what focal length you require.

Do you want a wide angle lens? A normal lens? A telephoto lens or a zoom lens? Those are probably easy questions to answer (but see Check the Quality below for more on this).

Go to your user manual and work out the focal lengths of each type of lens.

Zoom or Fixed?

As a general rule a zoom lens will have a smaller maximum aperture (not good) and be less sharp than a fixed focal length lens of similar price/quality.

If quality is important to you then fixed is often the way to go. A zoom lens has distinct advantages though. The zoom feature will help you shoot in a range of circumstances that a fixed lens won’t. If you are limited with funds and can afford only one lens, a zoom is probably the right choice.

Check Your Budget

This is a big one. In truth, you are limited by your budget. If money were no object then you’d buy a range of fixed focal length lenses and a few zooms too. Then you could choose the best lens for the job in hand. Most of us, however, are on a tight budget and we need to work out what we can afford.

Check the Quality

So Adobe Photoshop (and a whole bunch of other software) sharpens. But it would be great if the image you import is already pretty sharp and retains as much of the detail as possible that was present in the scene as you pressed the shutter release. This reduces the need for sharpening post-production.

Cheap lenses tend to produce less sharp images. Sometimes you can find bargains but it’s a good rule of thumb.

The only way to be confident about quality is to check a trusted review. Buy the magazines, search the Internet, talk with other photographers. Chances are you’ll be living with this lens for years to come – so do your homework! Get the best lens you can for the money you can afford.

Check the Maximum Aperture

The maximum aperture of a lens is the widest aperture to which it can be opened up. Some long focal length lenses can only be opened up to f/5.6. So if you’re shooting in dull conditions and could do with using f/4, you’re out of luck. Your only choice would be to up the ISO and hope the image noise is tolerable.

To produce a lens with a wide maximum aperture the manufacturer needs to use a lot more glass. More glass means more expense – both in terms of the glass and in the polishing, mounting and manufacture.

A lens with a wider maximum aperture is likely to cost a lot more than one with a smaller maximum aperture. So decide how you are going to use the lens and make a guess at the maximum aperture you’ll need.

Do You Need the Gadgets?

So lenses have stuff built-in. Anti-vibration, image stabilization and other such dark arts. Do you need that stuff? Image stabilization gyros, for example, can cause more camera shake if you use the lens on a tripod – so we have learned to turn them off some of the time. Will you be hand holding or mounting your lens on a tripod most of the time?  Search the Internet for the terms used in the marketing material – make sure you’re not paying for stuff you don’t need.

How to Choose a Camera Lens — Summary

Choosing the best camera lens for your needs can take some thinking about. Don’t just buy on impulse. Take your time and do your homework so you can choose a camera lens that’s going to be useful to you. Remember that the best lens for you could be different to the one a friend chooses.

  • Check trusted reviews from trusted sources.
  • Consider how you will use your lens.
  • Buy the best quality you can for your budget.
  • Remember that you’re probably going to have to live with your choice for some time.

This article’s thumbnail image was taken by Flickr user Vincent Diamante.

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