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4 Things To Consider When Buying A DSLR Lens

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How do you set about choosing which DSLR lens to buy? As if finding the right camera was not enough of an effort, DSLR lenses appear yet another minefield of jargon and complexity to deal with!

It can be tempting to just sigh and take whatever the nearest salesperson recommends in order to start taking pictures with your new gear.

But I'm going to explain 4 key things to consider whenever buying a new lens. It's all pretty simple really, and the most important thing is to be aware of the kind of shots you hope to take.

1. Focal Length

Different lenses have different focal lengths. This is one of the big advantages of DSLR cameras over compacts.

Focal length is not the distance from your camera to the subject, as people often imagine. Rather, it is the distance, in millimetres, between the optical centre of the lens and the image sensor inside the camera.

There are four basic categories of lenses based on focal length:

  1. Wide Angle. Focal length of about 35mm or lower (with a full frame sensor). These lenses take in a wide angle of view, making them great for landscape photographers.

    You can't zoom in very far, but are able to capture the full scope of landscapes and include plenty of foreground in a scene.

    A wide angle lens allowed me to include the flower and the sky here.

  2. Standard. Focal length of 35mm - 70mm. These lenses still allow you to take in a fairly wide angle, whilst also making it possible to zoom in a bit.

    They are great for candid shots - street and documentary type stuff. You can be in the midst action without having to go right up to someone to photograph.

    Standard FL is good for street/travel photography like this.

  3. Telephoto. Focal length of 100 - 300mm. Plenty of zoom and a narrow angle of view with these lenses. They are great for shots where you want to hone in on the subject and avoid all clutter in the foreground and background.

    Portrait shots look great taken with a telephoto lens.
    You can also get up close to sporting action and some wildlife.

    I took this shot at a protest march and, aside from the photographic value, I was happy to be at a safe distance from this chap with my telephoto!

  4. Super-telephoto. Focal length of over 300mm. Big zoom! Get right up close to wildlife and sport from a significant distance. These are what all those guys in the dugouts at sports games are using.

    You'll need a big camera bag to carry one of these, and they don't come cheap (hence why I have no pictures to show you taken with one!!) A great thing to have for sure - but only if you're certain it will be used a lot.


2. Prime Lens or Zoom Lens

Not all DSLR lenses have an adjustable focal length (e.g 18 - 70mm). Some are stuck on one amount (e.g 28mm). So the best digital camera lens will always have an adjustable focal length right? Well its advantage in terms of flexibility is obvious.


Fixed focal length DSLR lenses, or 'prime' lenses, produce images with greater clarity. So it's a trade off: Less flexibility and options for greater image quality.

Personally, I have not yet found the need to invest in a prime lens - flexibility always wins. But I can absolutely foresee a time when it would make sense, so don't write them off by any means. Especially because...

Prime lenses are cheaper. You may well find that the best digital camera lens for you is a prime lens. Perhaps you're a hugely keen landscape photographer - a wide angle prime DSLR lens will give you great quality, cost less and serve your purpose.

Some zoom lenses do produce image quality equal to fixed focal length DSLR lenses, but they cost a lot!

3. Compatibility

You're probably already aware that not all lenses work on all cameras. DSLR lenses are built to be compatible with camera bodies by the same manufacturer.

It's possible to transfer lenses between different cameras of the same make, but not between different cameras made by separate companies.

So it's important to choose a lens that fits with your camera body. The best DSLR camera lens built by Canon is no use whatsoever with a Nikon DSLR camera!

But, there are independent manufacturers who specialise in designing lenses. It's worth having a look at their offerings, not just because they are increasing in quality.

Some of these lenses are compatible with different makes of camera, which is quite a bonus if you think it's possible you might change your camera body in the future.

The best DSLR camera lens manufacturers of this kind are Sigma, Tamron and Tokina.


4. Maximum Aperture Width

The maximum aperture size (lowest f.stop) differs significantly between lenses. Why is this important? Well, chiefly because it's important to know how much flexibility you will have to shoot in different lighting conditions.

Basically, the wider the maximum aperture (the lower the f.stop), the more freedom and control you have. In low light digital photography, you need to let more light on to the image sensor through a wider aperture and slower shutter speed. The wider the aperture is able to go, the less demand on slowing the shutter speed - which can cause camera shake and a blurred picture.

This makes it easier to shoot clear pictures in low light, and freeze moving objects. Hence lenses with a wide maximum aperture are called "fast" lenses.

A fast lens helped me to shoot these candles without using flash

A wider aperture also gives you more control over depth of field (area in focus). A really wide aperture allows you to create a narrow depth of field and isolate a subject from its background. Apertures like f1.4 can produce lovely rounded blur (sometimes called bokeh)

It's worth looking for a DSLR lens with a feature known as 'image stabilization'. This helps alleviate the effects of camera shake when shooting on a slow shutter speed. It does not eliminate the need for a good maximum aperture size, but is a definite bonus nonetheless.

Many cameras have a variable maximum aperture size. As you zoom in, the maximum possible width of the aperture decreases. So some DSLR lenses will show a maximum aperture with 2 numbers, like: f 3.5 - f 5.6.

It's not a big deal, but if you really want to find the best digital camera lens, then a fixed maximum aperture lens is ideal. You retain complete freedom over exposure in low light, freezing of motion and depth of field, despite being zoomed in on a subject.

So that's it. I hope you find it easier to find the best digital camera lens for you after reading this guide. You're at least now armed with the most important camera lens information and facts to help you make an informed choice.

Remember, always have a clear idea of the kind of shots you want to be taking - and base your decisions about the lens specifications on that. The best digital camera lens to have will always be different for different people.

Where Next?

Compact Digital Camera Reviews

Digital SLR Camera Bags

Great Digital Photography Magazines

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