Tuesday, April 22, 2008

Aperture Bascis: Part 2 - Shutter Speed

Aperture Basics: Part 2 – Shutter Speed

Please keep in mind that, while this is one of the most basic lessons to be learned photography it is also one of the most fundamental and important ones, so pay close attention.

What we have covered so far, is that aperture greatly affects depth of field. What I have only mentioned in passing is that it also affects shutter speed.

What is shutter speed?

I’m glad you askedJ Shutter speed is the amount of time the camera’s shutter stays open, and consequently the amount of time light is allowed to enter the camera body and hit the sensor/film.

What is a sensor?

A sensor is a flat piece of silicon and plastic that sits inside of a camera where other film would be. There has to be something inside a camera to capture the light, and since there is no film, there must be an electronic sensor. If you have a question about this please leave a comment. There will be posts later on that go into more specifics about the sensor.

What does this have to do with aperture and depth of field?

Well, we have already established the link between aperture and depth of field. The reason aperture is linked to shutter speed is because they both influence each other. The lower your f-stop is, the more light you let in. When your aperture lets in a lot of light, your shutter doesn’t need to be open very long to let in a lot of light.

How can I use this to my advantage?

Below is an example of a situation where I didn’t care what my depth of field was, as long as I had a fast shutter speed(1/4000 of a second):

Here is an example where I needed a long shutter speed(20 seconds):

Now these are two very different examples of shutter speeds.

One froze motion, using a very high shutter speed, and consequently required a low f-stop to let in enough light to exposure the scene enough.

The other was very long and capture a lot of movement, which required a small aperture. The reason here being that, the lights on the ride were bright, but moving very slowly. In order to properly expose them while showing their movement for 20 seconds, I could only let in so much light over time.

The next post will be more practical examples of using shutter speed and aperture together, probably followed by a post on using ISO/ASA.

Friday, April 18, 2008

Aperture Basics: Part I - Aperture and Distance

Aperture and Depth of Field: Part 1

What is aperture?

Aperture is a type of measurement used by scientists to determine the half life of a nuclear reactor.

Well, no….

Aperture is a measurement, but is a number usually referred to as an f-stop. This number is a reference to how large the front element of a lens is opened compared to how long the body of the lens is.

So what?

Aperture affects a lot of things in photography, and is usually my first consideration when taking or setting up to take a picture. When taking a picture my first consideration is usually depth of field, which is linked directly to aperture and camera-subject distance.

The picture below has a very short depth of field, and is produced by being very close to the subject, and having a very low aperture (f-2.8). Please click the picture to see a larger version:)

The picture here has reasonably long depth of field, which was created by being somewhat far away from the subject(s), and here, more significantly a higher f-stop (f-16)

Now a more concise example of aperture:

Notice what is happening in these pictures. The distance stays the same, but the depth of field grows.

Why? The aperture is getting smaller and smaller, and the shutter speed is getting longer to compensate.

And the same of camera-subject distance

Now look at what happens here. The aperture stays the same, therefore the shutter speed doesn't need to change, but yet the depth of field changes.

Why? It's because the distance changed. The closer I got to the water bottle the more blurry the background got. This is because the focus was closer to me in each shot, rather than at a static distance like the first series.

As you can see, the distance and aperture both play a big role in depth of field. Try to think of them in this way:

For a short depth of field(blurry background) get close and use a lower f-stop.

For a long depth of field(clear all the way through) get farther away and use a higher f-stop.

Learn to use these rules to your advantage.

There is a lot more to depth of field and aperture than this, but I'm trying to cover this in little bites.

If you don't know how to adjust your aperture, you really need to at least take a peek at your manual, but I'll give you a starting place. You need to put your camera in A(Av for cannon) or M mode. Aperture mode(A/Av) lets you set the aperture with the camera setting shutter speed, and Manual(M) lets you set aperture and shutter speed. More on that later though.

In my next post we’ll explore the practical applications of aperture and distance, and what aperture has to do with shutter speeds.

Tuesday, April 8, 2008

Wow, what a mess...

Well over the last 2 weeks or so I've been trying to get blogger to unlock my page, and it finally happened. Thanks guys(if you're watching).

Anyway the next big thing here will more than likely be a guide on the basics of aperture based exposure. It may take a while to put together though, since I'm going to try and go a bit in depth with it.