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The Exposure Triangle: Aperture

So you've got yourself an SLR camera but you can't quite get the hang of shooting in manual. The foundation of understanding your camera is going to be utilizing and knowing what we call the exposure triangle. Today we are going to talk about Aperture.


Also known as the "f/stop", this is the only part of The Exposure Triangle whose

limitations are determined by your lens. Controlling your aperture controls how

wide the blades within your lens will open. What can be misleading is that the

lower the number, the larger the aperture. For example a very small aperture is

f/22 and a very large one is f/1.2.


The shutter speed is probably the easiest comoponent of The Exposure Triangle

to understand. It determines how quickly your camera's shutter will open and

close. A slower shutter speed will allow for more light to be let in your camera,

while a faster shutter speed will do the opposite.


By changing your ISO, you change how sensitive your camera's sensor is to light.

A higher ISO will create a lighter image, and vice versa. It should be noted that a

higher ISO will produce more grain in your image and soften the focus.


How do I take photos in a dimly lit room? How do I get that blurry

background? What do I do when I'm taking a picture of a large group of


The answer to all of these questions is to adjust your aperture.

I admit this may be the most difficult component of your camera to

understand but once you do, you will be able to do amazing things!


If you take a look at your lens, you will see some numbers with decimals listed. If

the lens is a zoom, then you may see two numbers. So what do these numbers


This number, or set of numbers, represent your lens's maximum aperture. For

example, if you have a 35mm 1.8, then your maximum aperture with this lens is

1.8. That is the most your lens can open to let in light. But what if your lens has

two sets of numbers? A common lens (also known as a kit lens, because it often

comes with your camera body) is the 18-55 f/3.5-5.6. HUH?! What does this

mean? That means that your maximum aperture will depend on the focal length

you're shooting. In this case, if you are at 18mm then you can dial your aperture

all the way up to 3.5 but if you zoom to 55m, the biggest you'll be able to get is

f/5.6. A prime lens (one that does not zoom) will have a fixed max. aperture. You

may find some zoom lenses with a fixed aperture, but these tend to be very



Maybe you've heard this term before but you don't really understand what it

means. Your depth of field (DOF), simply put, is the perceived distance between

two points in your photo. One of these points will be in focus and one will be

blurry.The larger your aperture (the lower the f/stop), the more shallow your DOF.

For example, you may take a close up shot of your baby's face with your aperture

set to 1.8. When reviewing your photo, you may notice that your baby's nose is in

focus but his eyes are blurry. However, if you take a few steps back and take the

photo with the same aperture, you'll see that your baby's face is now all in focus

and the background behind him is blurry.

Another example would be if you are photographing a large group of people. A tip

I've heard is that your aperture should match the number of people in the picture.

I'm not sure that I completely agree but it's good advice to some extent. If I'm

shooting a couple my aperture is going to be much bigger than if I'm shooting a

group of 35. That said my aperture for a couple isn't necessarily going to be f/2

and it will almost certainly not be f/35 for the large group. Distancing yourself

from your subject(s) is a good way to keep them in focus without needing to

decrease your aperture to much. Distancing your subject from the background is

a great way to create DOF without adjusting your aperture.


It should be emphasized that the aperture play an extremely important role in

creating a correct exposure in the camera. Remember, a lower number means a

larger aperture which means more light coming into your camera. A higher

number means a smaller aperture, and a darker image.


So now you know that shooting with a larger aperture gives you beautiful DOF,

with a creamy, blurred background (bokeh) and lots of light. So why would you

ever want to decrease your aperture? Well, there re actually quite a few

situations where a smaller aperture would work best. For starters, you may find

your images are not as sharp as they could be when shooting "wide open".

Turning your aperture up a few stops will help you create a sharper image. The

more you shoot with multiple lenses, the more you'll find that each lens has a

different "sweet spot" where it's sharpest. Of course, there are times when you

need an even smaller aperture. Shooting landscapes, or home interiors are two

times when a smaller aperture (higher f/stop) is preferred.

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