A Guide to Lenses

Good glass makes a massive difference to the quality of your images. I’d always recommend investing in better lenses before a new camera! But there’s a huge amount of technology surrounding lenses and thousands of different options on the market. Where do you start when you’re buying lenses? In this guide, I’ll explain all about lenses and how to choose the best for your photographic needs. 

Here’s what we’ll cover:

  • Definition of focal length
  • Prime vs Zoom
  • Pro vs Consumer
  • Third party vs Name Brand lenses
  • Focal lengths and what they’re generally used for
  • Specialist lenses
  • Sensor size and lenses

Definition of focal length

Lenses are named by their focal length – a 50mm lens has a focal length of 50mm. The focal length of a lens is an optical property of the lens – it measures the distance in millimetres between the optical centre of the lens and the camera’s sensor, determined with the camera focused to infinity. The optical centre is the point where all the light rays converge on the combination of lens elements that make up a lens to form a sharp image. 

Image 002 – Photograph by Mark Harpur 
 Wide-angle lenses are most commonly used for photographing landscapes.
Photograph by Mark Harpur | Wide-angle lenses are most commonly used for photographing landscapes.

Prime vs Zoom

First things first – there are two types of lenses available, prime and zoom. Prime lenses (also known as fixed lenses) just cover one focal length (e.g. 50mm), whereas a zoom lens will cover a range of focal lengths (e.g. 24-105mm). 

Optically, a prime lens will nearly always be superior to a zoom lens due to the fact that it’s only got one focal length to concentrate on. This also means that a prime lens will have one fixed maximum aperture (e.g. f2, f1.8, f1.4 etc) and they tend to be fairly large apertures, even on cheaper prime lenses. For example Canon make three 50mm lenses – f1.2, f1.4 and f1.8 with the f1.8 costing around $100. 

Cheaper zoom lenses, on the other hand, tend to have a variable aperture range – usually f3.5 – f5.6 and the maximum aperture you’ll be able to achieve depends on the focal length you’re using. This can be fine for a lot of general photography but frustrating if you’re trying to shoot portraits and want a small depth of field. If you want a zoom lens with a fixed aperture throughout its focal length, you’re going to be paying considerably more but you will have more options for shooting.

Zoom lenses are extremely useful if you’re shooting events, weddings, sports, or landscapes as it’s not always easier to physically move around and get closer / further away from your subjects in these situations. Personally though I’m a big fan of prime lenses – they’re light and unobtrusive and, I believe, encourage more creativity in photographers. That’s not to say that I don’t have zoom lenses in my kit for situations when they’re merited!

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Photograph by Matthew Henry | The classic standard lens is the 50mm, which gives the same field of view as the human eye.

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Pro and Consumer Lenses

Third-Party vs Name Brand Lenses

Alongside the lenses made by your own camera manufacturer (such as Canon, Nikon, Sony, Olympus etc) there are a number of third-party manufacturers making lenses with various fittings for different brands of camera. Three of the most popular third-party manufacturers are Tokina, Tamron and Sigma. In some cases, it may be that these manufacturers make zoom lenses that cover a focal length your own camera manufacturer doesn’t. But in the main, most third-party lenses have identical focal lengths and maximum apertures to lenses from camera companies. 

Why would you consider a third-party lens? In general they are cheaper than the name brand version, but many offer excellent quality and are worth considering. You do need to do your research though. Check reviews for a lens before buying (I’d do this for name brand lenses as well) and make sure there are no issues with sharpness, distortion or autofocus etc. 

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Photograph by Jessica Felicio | Telephoto lenses are ideally suited to portraiture, with the most popular focal length being the 85mm.

Focal Lengths and What They’re Generally Used For

Different focal lengths of lenses are grouped together to describe their functions. In general, lenses will be a form of either wide-angle, standard, or telephoto. Here are the accepted focal length brackets for each type of lens:

Super wide-angle < 21mm

Wide-angle 21mm-35mm

Standard 35mm-70mm

Telephoto 70mm-135mm

Super telephoto 135mm-300mm +

Do bear in mind that these are just general guidelines and that the brackets do overlap a little at each end – particularly depending on what manufacturer’s lens you are using.

What would you use these different lenses for? Obviously, you can choose to use a lens for any purpose but here are some guidelines to follow, as a general rule of thumb. Super wide-angle lenses tend to be used for architecture, wide-angles for landscapes, standards for documentary and street, telephotos for portraits and super telephotos for wildlife, birds and sports. 

Key Lesson: When you’re using heavier and longer telephoto lenses make sure you use a fast enough shutter speed to counter any lens and camera shake. As a general guide it’s advisable to use a shutter speed equal to or faster than the focal length of your lens. So, for a 200mm lens we’d recommend using a shutter speed of 1/200th or faster.  

Specialist lenses

As well as the standard range of lenses on the market, you’ll also find a variety of specialist lenses. Some of the most popular include macro lenses, which allow you to focus closer to an object than with a normal lens and give a 1:1 ratio. Tilt and Shift lenses are designed for architectural photography and have small bellows built into them to allow you to correct for perspective. And fisheye lenses are on the edge of wide-angle lenses, giving a distorted and curved view of your subject matter.

Image 005 gwen weustink I3C1sSXj1i8 unsplash
Photograph by Gwen Weustink | Super telephoto lenses are the obvious choice for wildlife photography, where getting too close to your subject wouldn’t be advisable!

Sensor size and lenses

A full frame camera has a digital sensor that is the same size as a 35mm negative. But camera manufacturers also make other sensor sizes with the most common being APS-C and Micro 4/3rds. These cameras are cheaper than full frame cameras and are widely used – both by consumers and pros. 

You do need to be aware that these different sensor sizes do have an effect on the perceived focal length of your lenses as they change your field of view. So, to work out the equivalent focal length you’ll be seeing, you need to multiply your lens’ focal length. This will either be by 1.5 or 1.6 for APS-C cameras (depending on the manufacturer) or by 2 for Micro 4/3rds. For example a 50 mm lens will give you the equivalent field of view of a 75mm, 80mm or 100mm lens, depending on the camera you’re using.

As you’ll probably be able to work out, this can actually be quite useful when you’re using super telephoto lenses as you’re essentially gaining without spending more money! However, it’s a bit more of a problem at the wide-angle end of the lens range. Fortunately manufacturers have acknowledged this problem and most make specific lenses designed for crop sensor cameras (for example Canon make a 10-22mm lens that only fits on their APS-C cameras and gives you an equivalent field of view of 16mm at the wide-angle end). 

In Conclusion

Good quality lenses are a key investment for your photography. Make sure you understand all the terminology that I’ve discussed in this article and do your research on any specific lenses you want to buy. Remember that cameras are improving and changing all the time, but a decent lens will last you forever if you treat it well!

Key Lesson: Whatever lens you invest in, please make sure that you protect it with a high quality super slim UV filter. These clear filters don’t make any changes to your image, will cut out UV rays from the sun and, most importantly, will protect your lens if you drop it. Replacing a filter will be far cheaper than replacing a lens! 

Self-help quiz

  1. What is a prime lens?
  2. What is a zoom lens?
  3. What might you use a super telephoto lens for?
  4. What does a macro lens do?
  5. What effect do different sensor sizes have on your field of view?

Cover Photo by Hunter Moranville

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