Lens roulette…

Most people buying a DSLR for the first time will opt for the kit lens to get a foot on the ladder and start snapping. For many - that will be all they ever need. There is, however an enormous array of lenses available for the beginner, wishing to expand their capabilities,  to choose from and all manner of advice from experts as to which is best for what purpose.

When choosing a lens, there are many features to look out for - aperture, vibration control, how the lens groups are arranged, how many blades make up the aperture - a bafflingly dense slab of data that you're expected to know all about before buying. This isn't strictly true unless you're after top quality, pin sharp results, but understanding the basics of what makes a good lens "good" is worth taking a few minutes to look into.

Lenses are best thought of as broken down into the following 4 groups:

Wide angle - anything below a focal length of 35mm (that's the distance between the lens grouping and your camera sensor). Typical wide angle lenses are around the 24mm area, with ultra wide lenses between 10mm and 24mm. Fish eye lenses fall into this category where the angle of view is dished out to around 180 degrees giving your images that characteristic distorted look. Wide angle is the lens of choice for landscape shots, architectural images and interiors.

Standard - these are lenses in the 35mm - 85mm region and are the nearest to how the human eye sees things. These are great for general shooting, portraiture, reportage and street photography.

Telephoto - these are lenses with a focal length above 85mm and are ideal if you want to zoom in on a subject. If you're floating 3 miles off shore and want to get a snap of Kate Middleton's shirt potatoes while she's on holiday - a dirty great telephoto is for you! Generally, the longer they are, the more unfeasibly expensive things get.

Macro - these lenses allow you to focus down really close to a small subject, such as an insect or dew drops. They're also labelled as "Micro" lenses by some manufacturers (Nikon in particular). They're offered in a variety of magnifications, and obviously - the greater the magnification, the higher the price!

Within the 3 groupings there is a further division: Primes and zooms

Zoom lenses - most people are more than familiar with how these work - everyone's phone has a camera zoom these days. Zoom lenses are available to cover all of the 3 groupings above and will mostly bridge from one to the other. They are distinguished by the focal lengths at either end of the zoom range - so for example, the Nikon kit zoom I bought covers a range from 18mm (wide) - to 55mm (standard). You can get zooms to cover any range you need within reason, from ultra wide to super long. Bear in mind that by offering a range of focal lengths in one, the trade off will be in image quality, so colour fringing and distortions will creep in, especially on cheaper lenses.

Prime lenses - these are lenses that are built to a fixed focal length - no zoom. If you want to zoom in on a subject you need to walk closer (or swim if your yacht's moored too far out). The great thing about primes is the image quality is far better, with very little colour fringing and distortion. They also typically offer a lower aperture (f number) which means they're good in low light and have fantastically small depth of field. This is the area of the image that is retained in focus before running out to blur - a good fast prime will allow you to have lovely creamy blurred backgrounds - known a "bokeh" behind your focussed subject. I'll be posting about this shortly, so keep an eye out.

Here are a few things to look out for when making a lens choice:

Price - You get what you pay for in this world and good glass is expensive. If it's a bargain, then it's probably been built down to a price and the results will eventually disappoint.

Vibration reduction - with some camera systems this is built into the body - with Nikon it's in the lenses. The latest version on Nikkor VR can gain you 3 or 4 stops of light and keep your images "shakey-cam" free. It's more of an issue on longer lenses, where camera shake can be a problem.

Autofocus - many older lenses are not compatible with some of the newer DX format camera bodies, so check this out before purchase. Many older lens designs relied on an autofocus system that was driven by a motor in the camera body and this is no longer available on many of the newer DX format cameras. The result would be a lens that you would have to manually focus - not a huge problem, but check it out before buying.

Sensor crop factor - this is an issue that could take a posting of it's own! Many lenses (unless they've been specifically designed for a DX camera) are built to work with cameras using a full size FX sensor. When these are used on a DX sendor camera (like my Nikon D3200) - the sensor, being smaller, will crop the image down so you will only capture the middle section. This effectively means that when using an FX compatible lense on a DX body, the focal length will appear to be about a third longer that it was designed at. A rough example of this would be: a 50mm FX prime on a DX body would give you images that are nearer 70-75mm. This works to your advantage with telephoto lenses as your 300mm zoom is now nearer 400mm (and much cheaper) - but works against you at the wide angle end, although the focal lengths are smaller, so it's not a huge problem.

It's an issue to bear in mind and if you're looking for a 50mm prime for your DX body, then you'll need to be buying a 35mm lens to achieve that!

Aperture blades - these are the sliding fins that open and close to form the aperture - the more a lens has, the sharper the end results will be, so a lens with 9 blades will perform far better than one with 5.

Lens speed - lenses with a really low aperture rating are known as "fast lenses" because they can let in more light and therefore run at a faster shutter speed. A low aperture rating will also give you the best bokeh if you're looking for creative blurring. For prime lenses, an aperture of f1.4 is really fast - with zoom lenses running in the f3-f5 range. The lower the figure - the more it'll cost! Fast lenses are always more expensive and when you get into the 300mm - 400mm range the costs can be prohibitive for all but the professionals.

Lens hood and bag - many manufacturers don't supply their products with a bespoke lens hood or any kind of bag or pouch to store it in.  This is a nice addition to look for if your manufacturer offers it as a bayonet fit hood is far better than one of the screw in after market types and a bag of some kind is essential to keep your new kit dust and scratch free.

Hopefully, this quick overview will help give you an insight into how the lens groups are divided and roughly what they'll offer you. As usual - if you want an expert opinion, there are plenty of great magazine and online reviews out there that are better qualified to give you specific advice. Buy the best quality you can afford and you prety much can't go wrong!

I'll be posting further lens related editions soon starting with every expert's must have lens - the 50mm prime and a further exploration of  "bokeh" and how you can use it to creative effect.

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