Exposure – Aperture and DoF

This is part of a four-part series on exposure.

Click here to read an overview of exposure, and for shutter speed and ISO.

Aperture

The opening to the camera lens is called the aperture. You are able control the size of this opening, in increments known as f/stops, thereby choosing the amount of light you want to let through the lens and into the camera in one go. The f/stop numbers go from small; when the aperture is at its widest, to large; when the aperture is small.

To demonstrate, here is a lens aperture at f/2.8:

Camera aperture at f/2.8

f/2.8

And here is an aperture at f/16:

Lens aperture at f/16

f/16

While the shutter speed lets you chose how long the light enters the camera, the aperture lets you choose how much light is able to enter in that time. Closing the aperture is known as “stopping down”, while opening it is “stopping up”. Even though modern digital cameras generally have the ability to be set to 1/2-stops, or 1/3-stops, the range of full f/stops is still useful to be aware of because it corresponds to the standard range of shutter speeds (which is also more varied on modern cameras).

Full f/stop range: f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32
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Exposure – Shutter Speed

This is part of a four-part series on exposure.

Click here to read an overview of exposure, and about shutter speed and aperture.

Shutter Speed

Last week we talked about basics of exposure – essentially what does what. I’d like to begin going into these in some more detail, starting today with Shutter Speed.

Shutter speed, aperture and ISO are inextricably linked together. To achieve your perfect image, all of them are equally important and they have to balance each other out. Sometimes this link is more or less obvious than at other times, but it’s always there.

There are countless combinations of these three elements that will grant you a technically accurate exposure… that is, provide enough light to show all the detail in the picture, without it being under or over-exposed. This is generally pretty easy to achieve; set your camera to auto and press the shutter button.

But the real fun begins when you start to look at possible photo opportunities with some understanding of the way each of these elements will affect your image. Then, instead of simply trying to get the right amount of light to create an “okay” looking photo, you can choose your settings creatively to gain the best result from the subject in front of you.

Before taking each photo you can think, “Do I want this whole scene in focus? Or do I want to isolate just one area and blur the rest?”, “Do I want to freeze the motion in my photo? Or would I prefer a stretch of sweeping motion-blur to create a different, more dynamic effect?”, and even, “Do I want this image to have a completely smooth finish, or would this subject be complimented by a more gritty, noisy texture?”

As you make a practice of thinking like this, and of experimenting whenever possible, more and more possibilities become obvious with every photo opportunity.

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Exposure – Shutter Speed, Aperture and ISO explained

This is the first part of a four-part series on exposure.

Click here to read more about shutter speedaperture, and ISO.

Exposure – an overview

No matter how manual or high-tech your camera may be, or what kind of photos you like to take, what photography really boils down to is exposure. It’s all about making sure the right amount of light reaches your film or electronic sensor to create the desired effect.

There are three things that affect the final exposure: the shutter speed, the aperture, and the ISO. Each one of these aspects works with the other two to create a perfect image.

It’s impossible to go into any kind of depth on such a huge subject with just this one post, so for today I’ll give a quick overview of all three from both a technical point of view, and a creative one. In the following weeks I’ll write about each of them in more detail.

1: Shutter Speed

The shutter speed is probably the most commonly understood aspect of exposure. This is the length of time the shutter is open for, thus allowing light onto the film or sensor. It’s a very simple idea; a fast shutter speed is open for a shorter time and lets in less light, a slow shutter speed is open longer and lets in more light.

The shutter speed is measured in seconds, and fractions of a second. For instance, 1/250 is a two hundred and fiftieth of a second, 1/1000 is one one-thousandth, and so on, and if you take the speed down you get to full seconds, such as 2”, which is two whole seconds.

Creative effect

Apart from the way they control the light, each one of the aspects of exposure has its own special influence on the image’s style. The effect of the shutter speed is the way it captures motion in an image.

A fast shutter speed will freeze action, which is great when taking photos of children, animals, drops of water, or anything else that doesn’t stay still for long.

I dragged my brother out into the cold garden this morning to juggle so I could demonstrate this for you properly. These photos aren’t works of art, but they get the idea across. The first photo was taken with a fast shutter speed; you can see the juggling balls frozen in midair.

(Photo taken at 1/1000, f/1.8, ISO 200)

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