Back to Basics: Aperture

[comycus]

What is Aperture?

Put most simply – Aperture is ‘the size of the opening in the lens when a picture is taken.’

When you hit the shutter release button of your camera a hole opens up that allows your cameras image sensor to catch a glimpse of the scene you’re wanting to capture. The aperture that you set impacts the size of that hole. The larger the hole the more light that gets in – the smaller the hole the less light.

Aperture is measured in ‘f-stops’. You’ll often see them referred to as f/number – for example f/2.8, f/4, f/5.6,f/8,f/22 etc. Moving from one f-stop to the next doubles or halves the size of the amount of opening in your lens (and the amount of light getting through).

One thing that causes a lot of new photographers confusion is that large apertures (where lots of light gets through) are given f/stop smaller numbers and smaller apertures (where less light gets through) have larger f-stop numbers. So f/2.8 is in fact a much larger aperture than f/22. It seems the wrong way around when you first hear it but you’ll get the hang of it. A better illustration of how aperture works:

[comycus]

Depth of Field and Aperture

Why is controlling aperture important? The most noticeable one will be the depth of field that your shot will have.

Depth of Field (DOF) is that amount of your shot that will be in focus. Large depth of field means that most of your image will be in focus whether it’s close to your camera or far away (like the picture to the left where both the foreground and background are largely in focus – taken with an aperture of f/22). Small (or shallow) depth of field means that only part of the image will be in focus and the rest will be fuzzy

Aperture has a big impact upon depth of field. Large aperture (remember it’s a smaller number) will decrease depth of field while small aperture (larger numbers) will give you larger depth of field.

(click on the photo to view)

To illustrate, the photo on the left has shallow DOF (Large aperture) while the photo on the right has large DOF (Small aperture). So clearly, when taking close up shots of our corals, we might want to achieve a shallow DOF to get the same effect as the photo on the left. However, when taking a FTS, we might prefer to use a larger aperture to get maximum detail.

It can be a little confusing at first but the way I remember it is that small numbers mean small DOF and large numbers mean large DOF.

http://digital-photography-school.com/aperture

[Ketchup]

hehe.. yes, it may be confusing at first. However, you have to remember that the DOF is display as a fraction. Hence 1/2 > 1/4 > 1/8 etc.