Photography Assignment: Aperture

Welcome back to Photography Class!  I've had so many people ask questions about Class over the last couple of weeks I want to direct your attention again to the FAQs.  I've updated the page and think it catches all the main questions.  To answer the biggest ones:  No, you don't have to tell me you want to participate!  Yes, you can jump in any time!  So join us, read the lesson, take some pictures and share them with the rest of the class.  We look forward to seeing your work.

Today we will begin to break down the ways light enters the camera and what we can do to manipulate that... and why we'd even care in the first place.

Lets begin with the WHY?  Why would I ever want to switch the camera out of auto mode and begin experimenting with the other scary settings on my camera?  Remember our goal?  To take pictures that are more like art and less like snap shots.  To do that we're going to have to learn about those other settings... and they aren't so scary once you understand how they work.

The three main ways we control exposure are aperture, shutter speed and ISO. Our job is to juggle these three things to create the best image possible. This lesson will focus on aperture.

The camera's APERTURE is the circular opening inside the camera that opens and closes when you take a picture.  A tight aperture lets in just a little light, a wide open aperture lets in lots of light.  Each setting of the aperture is called an f/stop.  The confusing thing about f/stops is that the larger the number, the smaller the opening.  The smaller the number the larger the opening.  It helps if you think of the f/stop as a fraction.  That way it is obvious that 1/1.8 is larger than 1/22.

There are two main reasons a photographer would want to adjust the camera's f/stop before taking a picture - Exposure and Depth of Field.

EXPOSURE
Remember that when the camera lets in too much light the photo is washed out and too bright.  On a very sunny day, or in the snow, you're going to want to let less light in your camera so your photograph isn't overexposed.  One way to do this is by closing down your aperture.  The smaller the aperture the less light will enter the camera.

When a camera doesn't let in enough light the photo is under exposed, dark with little to no details in the shadows.  When you're in a low light situation - indoors or at dusk - you're going to want to let in as much light as possible in order to properly expose your photograph.  One way to do this is by opening up your aperture.  The wider the aperture the more light will enter the camera.

Key Points So Far:
Bright light = overexposure SO use a smaller aperture to compensate
Low light = underexposure SO use a larger aperture to compensate


DEPTH OF FIELD
The other big reason a photographer would want to fiddle with the aperture is to control the depth of field.  Depth of Field is the amount of focus in an image.  A small depth of field will have the subject of the photograph in sharp focus with the foreground and background blurry.  A large depth of field will have most or all of the photograph is focus.

Aperture and Depth of Field are inversely proportional.  As the aperture gets bigger the depth of field gets smaller.  As the aperture gets smaller the depth of field gets larger.

Large aperture = small depth of field.  Small aperture = large depth of field.

(There are very technical reasons why this is true.  If you have lots time and high tolerance for details read this.  Note that the closer you are to your object the smaller the depth of field will be.)

Here are some examples.

This first one has a VERY small depth of field.  As you can see from the data below the image it was taken using a large aperture - f/1.8.  

Taken with a Canon Rebel XSi
Focal Length: 50mm
Shutter Speed: 1/250
Aperture: f/1.8
ISO: 400

More examples here.

This next one was taken with a very small aperture f/11.  It has a large depth of field and you can see all the buildings on the horizon are in focus as well as the little wind sock on the right hand side.

Taken with a Canon Rebel XSi
Focal Length: 50mm
Shutter Speed: 1/500
Aperture: f/1.81
ISO: 200


My suggestion when beginning to experiment with aperture is to set your camera on "Aperture Priority" mode.  This allows you to adjust the aperture and your camera adjusts everything else automatically.  For the most cameras it is the AV or A setting. 

Your assignment, should you choose to accept it:
1. Take pictures in bright light.  Get outside in this beautiful weather!  Set your camera to AV (or A) mode and start shooting.  See how adjusting your f/stop changes exposure.
2. Take pictures in low light. Take some pictures indoors or outdoors at dusk.  Set your camera to AV (or A) mode and start shooting.  See how changing your f/stop allows you to take pictures without using the flash. 
3. Take pictures with a small depth of field.  Take some pictures with a wide open f/stop for the purpose of finding a small depth of field.  Link your best one on the Assignment Due post next week.
4. Take pictures focusing on a large depth of field.  Take some pictures with a small f/stop for the purpose of capturing a large depth of field.  Link your best one on the Assignment Due post next week.
4. Read and research! Want to learn more?  Read this series by The Pioneer Woman.  She's fantastic and explains things much better than I do.