Exposure Variables ISO and Shutter Speed

Intro  Exposure and composition are dependent on three variables:  ISO setting  shutter speed  aperture setting

ISO setting  The ISO “speed” determines how sensitive the camera’s image sensor is to light.  A high ISO speed requires less light, but produces a grainier image.  A low ISO speed produces a clearer image, but requires more light.  Source:

Common ISO Settings  100 – bright, sunny day outside  200 – cloudy day outside  400 – well-lit indoor  800 – darker indoor situation  1600 – night/low light

Shutter speed setting  Shutter speed is how long the shutter “curtain” stays open to allow light into the camera.  A fast shutter speed allows you to “freeze” action in a photo, but reduces the incoming light.  A slow shutter speed lets in more light, but can cause motion blur in the photo  Source:

Shutter Speed setting  Setting number represents a FRACTION (250 = 1/250 of second)  Big number = less light  Small number = more light

Common Shutter Speed Settings  Common settings: B, 1 (1 sec.), 2 (1/2 sec.), 4, 8, 15, 30, 60, 125, 250, 500, 1000, 2000, 4000  Any number with “ behind it indicates seconds

Exposure Variables Aperture

Intro  The aperture is the size of the hole light passes through at the moment a photo is taken.  Source:

Aperture  The aperture setting is also referred to as f/number or f/stop.  A high f/number makes more things in focus, but reduces the amount of light entering the camera.  A low f/number makes backgrounds blurry and allows more light into the camera.  Source:

Common Settings  2, 2.8, 4, 5.6, 8, 11, 16, 22 (every other setting is twice as much or half as much light as last setting)

Depth of Field  Depth of field is the range of focus.  A long depth of field means more will be in focus – the foreground, middle ground and background.  A short depth of field means less will be in focus – the foreground only, for example.

In a nutshell…  The larger the f-stop (bigger number), the longer the depth of field.  The shorter the f-stop (smaller number), the shorter the depth of field.

Discussion Time  Get into groups of three.  Everyone in a group will receive a sheet of paper.  Everyone will get 30 seconds to write down important phrases about their word.  Each person will share what they know about the subject using only the words written on their sheet to help them.  Mrs. Bass will call on someone from each group to summarize what each group knows about the topics.

Equivalent Exposure

Intro  For each photo, there are multiple settings that will give proper exposure. This concept is equivalent exposure. A photographer chooses the settings based on the desired look of the photo.

Motion/Blur  If motion or blur is the biggest concern, the photographer sets the shutter speed first, and then sets the aperture setting.

Explanation  For each shutter speed increase, the aperture setting must decrease to give same amount of light.  Less time open, so opening needs to be larger.  For each shutter speed decrease, the aperture setting must increase to give the same amount of light.  More time open, so opening needs to be smaller.

Depth of Field (DOF)  If depth of field is the biggest concern, the photographer sets the aperture first and then sets the shutter speed setting.

Explanation  For each aperture setting decrease, the shutter speed setting must increase to give same amount of light.  Larger opening, so less time is needed open.  For each aperture setting increase, the shutter speed setting must decrease to give the same amount of light.  Smaller opening, so more time is needed open.

In a nutshell  When one goes up, the other goes down  When one goes down, the other goes up

Exposure Variables Reading the Light Meter

Intro  The lens light meter is built into the camera and reads the light that passes through the lens.  The meter displays the amount of light reaching the film based on the ISO, shutter speed and aperture settings.

Goal  The goal is to have the arrow in the center value, which is zero on our light meters, because this indicates proper exposure.  To reach this goal, the photographer will have to change the exposure settings until the indicator reaches zero.  Remember: Because of equivalent exposure and that there will be multiple settings to achieve proper exposure.

Explanation  The numbers below zero indicate that there is not enough light and that the image will be underexposed.  The numbers above zero indicate there is too much light and the image will be overexposed.

Underexposure  If the light meter shows underexposure no matter how much you change your aperture or shutter speed, both settings need to go down and the ISO needs to increase.

Overexposure  If the light meter shows overexposure no matter how much you change your aperture or shutter speed, both settings need to go up and your ISO needs to decrease.

Discussion Time  Get into groups of three.  Everyone in a group will receive a sheet of paper.  Everyone will get 30 seconds to write down important phrases about their word.  Each person will share what they know about the subject using only the words written on their sheet to help them.  Mrs. Bass will call on someone from each group to summarize what each group knows about the topics.