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Photographers are notorious for never having enough. If you’re not there yet, you might be soon.

Lenses make the perfect excuse for us to compare specs, shop prices, and generally nerd out about brands and models. And it’s actually justified by the fact that the lens on the front will make more of a difference than the number of megapixels your camera is endowed with.

If you don’t know what you want, or even if you don’t know what different lenses do, it’s time to get some of our super friendly hands on training, or at least hit the internet for pictures people have taken with the lens you are interested in.

Make sure someone actually owns the lens before you ask them for advice. And ‘owned’ (past tense) is more common than we all like to admit as many of us had to sacrifice something to get the shiny new one. I have both hands in the air right now shouting “Guilty!”

When cameras first became widely available to the public, you couldn’t change the lens on the camera. Kodak’s Box Brownie was aptly named. It was literally point, push the button and Kodak proudly ‘did the rest!’

Then cameras got smaller, and smarter and you got to change things like the shutter speed and the aperture on the lens. But the feel of a photo depends a lot on the length of the lens which nowadays is measured in millimetres (regardless of your refusal to embrace Metric) and called ‘focal length.’

Eventually manufacturers allowed us to choose a model with the lens we wanted, then they very quickly worked out there was more profit in making cameras that you could change lenses on.

And when they invented zoom lenses, they really hit the jackpot because most of us are terrified at having ‘just one focal length’ because we don’t know what to do.

Why zoom lenses?

Well, you can have a wide lens or a long lens (not sure why we don’t say short or long, or wide and narrow). You can have your cake and eat it. In theory. Mostly it’s convenience.

The longer the lens, the narrower the angle of view. It’s a bit hard to explain or imagine the difference between 90 degrees and 100 degrees, so we’re stuck with mm as the language used to compare.

A long lens has a narrower angle of view, and because of its relationship with the sensor, it has less depth of field (how much is in focus between the camera and the subject). The longest lens in a typical photographer’s kit is 200mm. That’s because it’s the end of a 70 to 200mm zoom lens, a lens ubiquitous in every manufacturer’s line up.

That’s a size that actually creates a little compression (roughly speaking it makes noses appear a bit smaller and ears don’t appear to stick out). It also renders the background out of focus, and we don’t see a lot of it. Therefore, the 70-200 is the workhorse of fashion and portrait photographers.

At the other end, the 24 -70mm lens is super popular for being able to work amongst the action, and still zoom into a face in a group without moving your feet. It’s a popular lens for journalism and travel photography. At the wide end, the closer you get to your subject, the opposite of a long lens starts to happen. Noses, or any other appendages closer to the lens, start to balloon out. And because you’re using a wider angle of view, there is much more background in the picture, and it’s much more in focus. But you can use the 70mm end for portraits, and the 24mm end for group shots or ‘scenes’ where you need to see as much as possible in frame and/or in focus.

Some people can live with just one of, or certainly both of, these zoom lenses, or their equivalent size depending on their camera’s sensor size, hardly ever changing lenses even though they have a mirrorless or DSLR that can change lenses. It helps that the lens quality is usually vastly superior to the lenses built into compact or bridge cameras.

So why do prime (a.k.a. fixed focal length) lenses still exist? Once you rule out convenience, you get a host of reasons. Zoom lenses are expensive and difficult to design and build. They have to make a large number of optical and mechanical compromises. They are bigger and heavier. Did I mention zoom lenses are way more expensive?

Ignoring price (primes are usually far less expensive), primes are considerably sharper with much better control over optical problems such as ‘chromatic aberration’ (the purple or green fringes around contrasting edges in your photo) and flare (light from the edge of frame washing out colour and contrast in the rest of the image). Additionally, every lens suffers from optical distortion, either barrel distortion, or it’s opposite pincushion distortion which is much easier to design out of a prime lens.

Common prime lenses are 24mm, 35mm, 50mm, 85mm, and 135mm. There are of course hundreds of options all the way out from 4.5mm to 1300mm even specialty lenses longer than that the size of a small car.

One of the huge differences (other than sharpness) that photographers obsess about is how ‘fast’ a lens is. This is how wide the lens opens up and is expressed as the aperture more commonly measured as a f-stop (that sounds wrong, but it’s correct grammar).

Primes can go from f/.95 to f/64 but more commonly f/1.4 to f/16. The smaller the number (because we are dividing by that number) the wider or more open the iris (the circular metal blades inside the lens). So f/1.2 is wide open (and expensive!) and f/32 is a comparative pin prick.

As you ‘stop down’ or close the aperture, you decrease the amount of light getting through to the sensor, but magically (okay, it’s optics, not magic, but you try doing it) you increase how much of the image is focus. Of course this means as you open the lens up, you get more light in, but less is in focus from front to back.

I mention the obsession about f-stops? People drool over ‘fast lenses.’

There is one (seriously, just one) zoom lens that opens all the way to f/1.8. The next most impressive zoom lens is f/2 and is a seriously engineering achievement. What’s more impressive is that they are both quite sharp. It turns out that the wider you make the aperture, the harder it is to render a sharp image. Many older prime lenses (many Canon designs are in the double digits for age) get very ‘creamy’ (that’s not the technical term) at wider apertures, and most lenses ‘vignette’ (get darker around the edge of frame). f/.95 lenses are notoriously un-sharp wide open with a lot of other optical issues, so you have to judge if that’s worth it for being able to see in the dark, because despite not being technically perfect you can get some astounding results in low light.

Adobe Lightroom has a variety of tools for correcting all these issues, and we are an Adobe certified training facility and can teach you all the joys of Lightroom without the mind-numbing panic of learning such a vast program. Or we can teach you how to fix it all in Adobe Photoshop; we have hands on training. Of course it’s better not to have these problems in the first place. Come and learn to enhance your images artistically instead of just technically.

Now the other thing about those extreme wide open lenses? The depth of field can be so shallow that you can’t get both eyes in focus. Sometimes all you’ll get is half an eyelash. I am not joking.

A lot of TV shows are filmed (with the same lens designs and sensors as your APSC DSLR or newer mirrorless) at f/4 because we like things to be in focus – especially an entire head. For photographers, it’s a matter of taste. Photojournalists are instructed with the mantra ‘f/8 and be there! Because it’s more important that people are in focus. The shallower your depth of field, the harder you or your camera have to work to get the focus right.

There is no point in an f/1.2 lens that can barely focus and is actually less sharp than the (vastly!) cheaper f/1.8 version of the lens from the same manufacturer.

Zoom lenses are cursed to basically limited to f/2.8. That’s more than enough. But if you’re like me and you realised you like your photos in focus more often, buy the f/4 lenses. They’re less than half the size (they literally need less than half the diameter of glass) half the weight and nearly half the price. And just as sharp.

Just make sure you look for a lens that is a constant f-stop throughout its entire zoom range – otherwise as you zoom in, you lose exposure and have to compensate. Cheap lenses / kit lenses often start at f/3.6 but quickly fall off to f/5.6. They also quickly degrade in image quality at one or both ends of the zoom range and their sharpness is measured for the sweet spot – it’s often up to you and the internet to work out where the sweet spot is.

Cheaper photography lenses change their focus point as you zoom in and out. You have to refocus every time you change the zoom position. One that stays where it’s focused is called a ‘par-focal’ lens, and it’s why zoom lenses for cinema or video cost the same as a new car (a sedan, not a hatchback!) because you can’t have the shot go out of focus as you zoom. Also lesser lenses ‘breath’ when focusing – the images size shifts as you focus (a small but noticeable zoom in or out).

At the other end of the f-stop, past f/8, the tiny aperture creates its own problems and as you stop down. The image degrades (no) thanks to diffraction. It’s best to not go past f/16 and most lenses are at their tippy-toe best at f/5.6. Some lenses are designed to be (exactly) the same at every f/stop (excellent) but have glass in them costlier than gold. You pay accordingly. Even they, however, suffer from diffraction.

So just to repeat, go too wide open and the image degrades. You usually get hit with flare (milky white haze), softening and dramatic loss of contrast (a 2nd symptom of flare). Go too far the other way, typically f/16 and above and you get diffraction which softens the image due to distortion. f/4 to f/8 is the sweet spot for most, and the better lenses give you a bit more range.

I like primes (fixed focal length) lenses. They have less optical issues, they’re cheaper and are often smaller. The higher quality ones are usually made of metal, so they can be as heavy as a zoom that’s built of plastic to cover its weight.

Primes often feature faster autofocus because they have less glass to throw around.

It’s true that good zoom lenses tend to be large and expensive, but there is the convenience…if you can overlook them being inconveniently slow, bloated and, generally speaking, nowhere near as sharp as a prime lens.

Travel and journalism?

Zoom baby zoom! For the rest of us, especially if you are in control of the environment / photoshoot? Primes! At least get 2 – one for either end of the zoom you were considering. You’ll save a ton of money. Youwon’t need a masseuse at the end of the day (actually, that might be a plus). Most importantly, you get sharper images with a prime lens.

And one last thing to think of. Different cameras with interchangeable lenses have different sensor sizes. The 3 most common are Micro Four Thirds (MFT)a bit larger than an inch, APSC (Nikon calls this DX) the size of motion picture film, and Full Frame (the size of a traditional 35mm piece of film in a stills camera. There are a lot of 1” chips, often found on ‘Bridge Cameras.’

The smaller the sensor, the more depth of field you get. Full frame has half the depth of field of APSC, so focusing that f/1.2 lens everyone raves about is stupidly hard. MFT has trouble getting the background out of focus on wider lenses.

On top of that, due to the differences in sensor size, the way the focal length plays out is different. We use Full Frame as the standard, and then use ‘equivalent to’ for most other cameras. Compact cameras and bridge cameras use the ‘equivalent to.’

For APSC, multiply the lens’ focal length by 1.5 (1.6x for Canon). A 35mm lens on an APSC camera has the same field of view as a 50mm on a full frame camera. All your lenses become longer.

50mm is the most natural size (angle of view) for a full frame camera, it’s 35mm for an APSC. This is the focal length that matches how our eyes see things. Your iPhone camera is equivalent to 35mm full frame, or 24mm APSC.

Micro Four Thirds has a ‘crop factor’ (how much you multiply the lens length to get the same angle of view) of 2x. So a 25mm on a MFT camera is the same as 50mm on a full frame.

And finally, glass for APSC or Micro Four Thirds is smaller because is physically spreads the light over a smaller area. This means you can’t use MFT or APSC glass on a full frame camera – the lens won’t cover the entire sensor with light. Great news for you? APSC and MFT lenses can be much smaller, lighter and cheaper.

If you use full frame lenses on (most commonly) APSC cameras, your sensor is only using the best part of the lens, the middle! This gets rid of all the optical flaws that live at the edges of the lens (corners of the frame). I often buy full frame glass for my APSC cameras for this reason. Just remember to multiply the focal length to suit your smaller sensor. That 50mm becomes a 75mm lens (just perfect for portraits) on your Nikon DX (a.k.a crop sensor), or 80mm on your Canon APSC.

And if you’re dizzy by now with all this information, come and try this out in the comfort of one of our photography workshops, and you’ll learn it all by doing it!

And if you’re dizzy by now with all this information, come and try this out in the comfort of one of our photography workshops, and you’ll learn it all by doing it!

Written by:

Deane Patterson

Everyone here at BYOL believes in sharing. We ensure part of our profits every month goes to wonderful charities doing amazing things.