what is aperture

What is aperture?

Learning anything new comes with a whole spectrum of principles, terminology, and practices that have the potential to boil your brain, leave you mildly confused, or anywhere in between whilst you're getting to grips with them. Photography definitely comes with its own theories, vocabulary, and conventions and not knowing what people are talking about when they refer to 'noise' or 'speed' can make you feel about a pixel tall. To try to ease people's paths in photography and prevent eye-swivelling, mind-frying, and either mild or acute embarrassment, we're running a series on photography fundamentals, throwing a bit more light on the things you need to know. I could say that we're starting with aperture because it begins with a, but I'd be lying. We're starting with aperture because it was the first thing that sprang to mind.

Aperture: it might be basic, but it can also be a bit of a stumbling block for people who are just beginning in photography. For a start, altering aperture doesn't have a single effect on your images, but a dual one. As if that isn't enough to confound people, its scale isn't exactly intuitive. Still, understanding aperture is critical for both exposure and composition—the bedrock of photography—so we'd best crack on.

Aperture and light

Aperture means ‘hole’ or ‘opening’. In a photography sense, the aperture is the gap that allows light to pass through the lens. The bigger the opening, or the aperture, the more light passes through. That’s pretty intuitive. When you’re taking pictures in low-light settings, a bigger aperture will help you to take a photo where you can see something.

In order to get enough light onto my sensor, I used an aperture of ƒ/1.8 here

If you’re taking pictures in bright sunlight, using a smaller aperture will help to prevent the image being one mass of white.

Aperture and depth of field

The second effect that aperture has on photographs concerns depth of field, or how much of an image is in focus. If you use a small aperture, you will notice that the depth of field in your photos will increase: more things in the background and foreground will be in focus. Landscapes often benefit from small apertures. In this case, ƒ/11 was used to photograph Mount Etna

Conversely, by increasing the size of your aperture (and allowing more light to reach your sensor), you will decrease the depth of field in an image. That means that less of the scene will be in focus.

Sanguinello

An aperture of ƒ/1.8 meant only a sliver of this blood orange was in sharp focus

Measuring aperture

When you hear people throwing around numbers such as ƒ/1.8, or ƒ/22, they are referring to aperture. Aperture is measured in ƒ-stops, with ƒ/1.4 being a very big aperture and ƒ/22 a very small aperture.

That the large number represents a small aperture and the small number indicates a large aperture can be more than a bit confusing. It will probably help to think of the ƒ-stop scale like this: those numbers correspond to fractions; the fraction being how big the aperture—or the opening—is. Thus ƒ/4 corresponds to a quarter and ƒ/8 to an eighth. An eighth is obviously smaller than a quarter; this means that it is a smaller aperture, it lets in less light and it gives a greater depth of field.

Finally, perhaps you're wondering what those fractions are fractions of? They’re fractions of the length of the lens you’re using. The aperture of a 28mm lens at ƒ/1 will be 28mm. Similarly, the aperture of a 50mm lens at ƒ/4 will be 12.5mm. The bigger the ƒ-stop, the smaller the aperture.

TL;DR

  • Aperture means hole, gap, or opening
  • A smaller aperture lets in less light, good for shooting on sunny days; a larger aperture lets in more light, good for shooting when it's dim
  • A smaller aperture gives a greater depth of field, bringing more of the background into focus; a larger aperture gives a shallower depth of field with less in focus
  • Aperture is measured in ƒ-stops
  • F-stops correspond to fractions
  • The higher the ƒ-stop number, the smaller the fraction, and the smaller the aperture

You know what, go out and take some photos altering the aperture value on your camera. Then you’ll see what we mean!


Photography Fundamentals >> Contrast

Photographing in the dark

The Magic Numbers, by Gareth Dutton

Photographing in the dark can seem a daunting and difficult task when encountering it for the first time, but here at Small Aperture we have a few quick pointers to help you out. Hopefully this article will, wait for it, shed some light on the subject (I’m so, so sorry). So what can we do to combat low light photography? There are, thankfully, several options available to us.

Use a larger aperture

I shot this at f/2.8 at ISO 1600 - the shutter speed needed to remain high.

One option is to work with a larger aperture. What is aperture, you ask? Well I’m shocked and appalled, quite frankly, that you haven’t already read up on our article about it. The bigger your aperture, the more light you’re going to be letting in. Of course, sometimes, you can’t afford to / don’t want to lower your aperture. Whatever shall we do? Well, you could always…

Increase your ISO

Increasing your ISO will increase your sensor’s sensitivity to light, which will help make the most of what little light you’ve got to work with. What are you talking about Gareth? What are these kooky letters you’re putting together? As always, we have it covered – nip over to our guide to ISO and then come back to me when you’re up to speed.

All done? Good. So, increasing your ISO can help you capture those precious, delicious slivers of light skulking around in the darkness. But what about all this horrid noise? It’s spotty and grainy and yucky – this won’t do at all. Well, how about we only increase the ISO a tad and look at changing some other settings?

and this one required all three - ISO 1600, aperture of f/2.8 and a shutter speed of 1/100. Take THAT, low light!

Lower your shutter speed

Lowering your shutter speed can also help your camera gather more light for when there is little to play with. Guess what? We have this one covered, too – take a look here. The longer we have the shutter open for, the more time light has to get in. Too low a shutter speed can lead to image blur, however, and unless you’re going for that look, images that aren’t sharp are, well, unsharp. Image still too dark? Well, I’m afraid that’s all your options exhausted. Bummer. Or is it…?

Get yourself a tripod

Go on, do it now. Open a new window in your browser, go to Amazon, and get it ordered. Unlike other things in your kit, a decent, sturdy tripod doesn’t really ever need to be replaced for a newer model and should still be useful for years and years to come. This means you’ll have to give it a name, of course. Mine’s called Trev. Trev the Tripod. Trev has always been there for me when I’ve needed him. The best thing about Trev is, when I need to lower my shutter speed to a duration for which I couldn’t possibly hold my camera still, I pop it on Trev and he keeps it perfectly still for the whole exposure.

Good old Trev.

You’ll mostly find a tripod useful for grabbing yourself some lovely sunset / late evening landscapes, which will afford you to work with a very small aperture AND a low ISO setting in order to get some lovely, low light landscapes.

Let’s summarise, then.

To defeat the low-light menace, try a combination of these factors:

  • Use a larger aperture
  • Increase your ISO
  • Lower your shutter speed and, if it’s too low for a sharp image…
  • …Use a tripod!

Depending on what sort of image you’re after, you’ll be using a combination of these for one image and maybe just altering a single factor for another. There is no greater teacher than experience, so get out there armed with this new-found knowledge and experiment! Seeing as it’s Friday, if your friends invite you to the pub just tell them ‘Can’t make it tonight, I’m afraid; I’m spending the evening in a field with Trev.’