Beginners guide to choosing the right lens


Beginners guide to choosing the right lens


Camera lenses laid out on table


Your camera lens is crucial to taking any photograph. Without the lens, the camera is useless.

Photography is about capturing light, and the best camera sensor or film will suffer if the lens, the device capturing the light, is poorly made.

Good lenses last years, are updated infrequently by manufacturers, and therefore are likely to outlast several camera bodies. There is a great used market for lenses, with some lenses holding their value years after they ceased production because they became synonymous with quality.

Lenses have characteristics such as bokeh, contrast, or sharpness that matters, and individual photographers wax lyrical as they talk about the esoteric “character” of a lens.

This article is not going into a deep dive on specifics such as this, but more an introduction into choosing a lens and the points to consider.

Lens mounts and adapters


Lens adapter on Canon camera


Each manufacturer has their own lens mounting system, and often different mounts for their different lines of camera. This article from photography Life delves into the different mount types in detail if you want more technical information.

Because of physical attributes, mainly flange distance, systems such as Micro Four Thirds have a short flange distance making it possible to adapt lenses from other camera systems with longer flange distances via adapters, whereas the opposite is not true.

You need to ensure your lens choice will fit your camera body directly, or if a quality adapter is available; with A/F if needed. 


Prime or Zoom


Prime and Zoom lens standing on table



A prime lens has a fixed focal length and the advantages are:

  • High Quality images
  • Wider apertures
  • Smaller in size
  • Relatively cheaper
  • Encourages you to explore the scene more by moving around.


  • Single focal length means moving the camera to zoom in or out.
  • More expense if you need many focal lengths

A zoom lens has variable focal lengths and the advantages are:

  • A variety of focal lengths in one lens to move zoom in or out without moving the camera.
  • Convenience and weight and no lens changes to get wider or closer.


  • Quality over a prime lens
  • Usually slower apertures, particularly at the long end
  • Expensive if you want large aperture constantly across the range


Aperture and Depth of Field (DOF)


Your choice of aperture is the single most controllable element you have of the exposure triangle, the other two being ISO and shutter speed. ISO quality will be decided by the sensor or film choice, and shutter speed the camera body.

Aperture choice dictates the amount of light the lens can gather into the camera, and is defined by the size of the aperture. The “f-number” as it’s known increases as the aperture size decreases, as can be seen in the above image. Note that as the f-number increases, the size of the aperture counter-intuitively decreases.

Often referred to as the “Speed” of the lens, an f/1.4 aperture would be called a “fast” lens as it can capture a lot of light quickly due to the size of the opening at this setting. Lenses starting from f/4.5 would be considered “slow”.

A larger aperture allows a faster shutter speed, so if you want to photograph moving objects and/or in low light, then a faster lens becomes essential.

Fast and slow are not necessarily positive and negative attributes, as we need to consider Depth of Field (DOF). Depth of field is defined as the distance between the closest and furthest objects within a composition, both of which are in focus, and is a direct function of aperture size and subject distance, and changes with the focal length - a wide angle lens such as 12mm gives a much deeper DOF than a 300mm telephoto.

A fast wide aperture gives a smaller DOF, and a slower small aperture a longer DOF.

If you want/need your subject to be tack sharp with everything behind out of focus, then a fast lens/wide aperture would give you that, as in the dog photograph below. The depth of field is very short - between the nose and the back of the eyes. Great for portraits.


Dog face with small DOF


For landscapes and images where you want more in focus, then a smaller aperture and subsequent larger DOF is necessary, as in the landscape below.


Landscape with large DOF


Or even smaller subjects.




Another article from Photography life also digs deeper into aperture than we want in this blog, and is a very useful resource for this important attribute of lenses and how they affect your images. They also do a great article on DOF.

  • Fast lenses allow faster shutter speeds for low light/moving subjects
  • Fast lenses allow shallow DOF
  • Fast lenses are more expensive, and those at f0.95 and f1.4 are premium priced prime lenses.

So if you’re a landscape photographer, you don’t need to pay the premium for a fast lens, and the money will be better spent on a wide angle lens, as you’d be constantly reducing the aperture size (Increasing the f-number) for landscapes.


Focal Length - typical uses 


Focal length in simple terms refers to the magnification of the lens, with a larger number meaning more “magnification”. In the above image, from another article here on TARION, the picture was taken at 12mm across a cityscape: a “wide” angle of view. Then a 75-300mm zoom lens was added and the two coloured overlays represent the angle of view at 75mm, then the narrower “zoomed” 300mm.

See the full pictures from 75mm and 300mm, and other comparisons here.

For 35mm Full Frame cameras, the focal lengths to consider for each type of photography are:

8-24mm are called ultra wide angle lenses and offer a very wide angle of view. There is a large amount of distortion (especially with “fisheye lenses”). They are ideal for interiors, wide panoramic landscapes, cityscapes and architecture, and offer creative/artistic options when using the distortion.

24-35mm are normal wide angle lenses and offer a very wide angle of view, but with less distortion than ultra wide angle or fisheye lenses. Suitable for architecture, landscapes and group portraits.

35-85mm are often referred to as standard lenses. They offer a more accurate reproduction of what the human eye sees in terms of perspective and angle of view compared to ultra wide and wide angle lenses, specifically 50mm.For this reason they are popular carry-around lenses for many photographers, and often this range is included as a “Kit” lens when buying a new camera

85-135mm are called short telephoto lenses and are an ideal lens choice for portraiture. They offer a flattering and accurate perspective of your subject and allow you to work at a reasonable distance from your subject to put them at ease.

100-800mm are generally referred to as just telephoto lenses Very popular with sport or wildlife photographers, they can also be used for a variety of subjects as they pick out detail from afar on landscapes, cityscapes, or candid shots of people.

800-2000mm are called super telephoto lenses used by professional sports and wildlife photographers. They are specialist lenses, very expensive, and heavy. Photographers often  rent lenses like these for the occasional times they need them.

If you’re not sure which lens you’d need, you could borrow or rent a lens and try it for a while to see if it suits your image requirements.

A note on crop sensors

Please note that for crop cameras, the numbers are different. For example, Micro Four Thirds cameras have a crop factor of 2, so an f2.8 50mm lens on that camera system is equivalent to an f2.8 100mm lens on a Full Frame system, although the DOF would be equivalent to f5.4, so the DOF is greater.

Here is an excellent and honest explanation of crop factors, amongst a tsunami of misinformation across the internet, by Wolf Amri. He covers the strengths and failings very well.

The important thing to remember is that a crop sensor of 20 megapixels will give a 20 megapixel image for the field of view it is capturing, so a 50mm lens on e.g., Micro Four Thirds is a 20 megapixel image that would take a 100mm lens to capture on a full frame system; with the difference being DOF and perhaps ISO and dynamic range. (Smart phones have a 7x crop factor and still produce excellent images.) Many professionals use Micro Four Thirds 2x crop factor as they cater for 95% of any photographer's requirements in a smaller, lighter, cheaper body and lens system. Where crop sensors do suffer, professionals go to either full frame or medium format to get those specific needs fulfilled.


Your shooting history


Often you know when you’ve needed more reach with a telephoto, or a wider angle to get a shot, and that leads you to want a new lens. 

If you have a digital photo library application such as Adobe’s Lightroom, then you can search the exif data and see how many times you used a particular focal length or aperture. 



I discovered I took a lot of pictures at 12, 17, and 25mm and bought primes at those focal lengths. The difference in picture quality and “character” of the lenses was a surprising treat. I also discovered a lot of shots at 150mm, the limit of the 40-150mm f2.8 pro zoom, so kept the kit 75-300mm that I use for that extra reach until I can afford a longer prime or zoom as clearly I was using the limits of that lens.

So your experience, aided by software, can determine which lens may next be on your list.






Many argue lenses are a better investment than camera bodies, and if you’re serious about quality then buying the best lens you can afford for a particular need/want is a better investment than upgrading. 

Used lenses often come on the market at far less than new prices. Online auctions and general second hand/used sites are fraught with danger unless you know what you’re doing, or can meet the seller to check the condition of the lens.

Searching your internet forum sites to see who’s offloading gear, or established used gear stockists, can be a good source. 

Your local bricks and mortar shops, that need our support to stay in business, are an opportunity to test before you buy, and perhaps seek advice from the often experienced staff on hand. 

Scratches/scuffs may indicate the lens has been handled roughly. Shake the lens and see if it rattles, as that may indicate internal elements are loose. Check for scratches on the lens and dirt/mould behind the lens. Finally, check the aperture blades are clean and intact, as are the electronic contacts and lens mount to the camera.

Final thoughts

It’s worth taking your time and being patient. If you’re struggling to find something in your budget, wait and save more. You’ll regret buying something where you’ve made sacrifices because of your budget and will probably immediately regret it; paying more later to buy the lens you really wanted/needed. 

A lens is a long term investment and, as has been said, often more important than the camera body in capturing the images you want.

Patience is a virtue in photography, as is learning and preparation. The same applies to choosing the tools of your craft.

Do you have a story of poor lens choice, or perhaps how a new lens changed your images for the better?