PHOTOGRAPHY BASICS

Exposure

Alan Louie

Jul 2010

Overview

Controls of your camera The Trinity of Light

ISO, Shutter Speed, Aperture Getting the right exposure

The Histogram

Camera Controls Auto – Camera completely defines

how the picture is taken Program – Camera sets exposure but

takes in account ‘exposure compensation’

Shutter Speed Priority – You set the shutter speed, it sets F-stop and ISO*

Aperture Priority – You set the F-stop, it sets shutter speed and ISO*

Manual – You set it all

* - Only if camera has auto-ISO

Trinity of Light

The amount of light captured

Aperture/F-stop

Large Aperture, Low F-stop

Small Aperture, High F-stop

Shutter Speed

Fast Shutter Speed

Slow Shutter SpeedLow ISO

High ISO Sensor Sensitivity (ISO)

Freezes Action

Motion BlurHigh “Noise”

Low “Noise”

Large Depth of Field

Shallow Depth of Field

Aperture/F-Stop Aperture is how large the iris in the lens/camera opens

to let light through F-stop is a measure of Aperture in an inverse measurement.

F2.8 is a very wide open aperture while F16 is a very tiny Aperture

The larger the Aperture, the less Depth of Field

Depth of Field

Focal Point

1/3

2/3

Depth of Field Examples

Shutter Speed Shutter speed defines how fast the mirror or

shutter opens to allow light through, then closes Rule of Thumb: 1/Focal Length = Minimum

shutter speed when hand holding Use a tripod or a monopod for lower shutter

speeds on static subjects Usual Shutter Speeds

Static Picture - Walking ~ 1/60sJogging/Dance ~ 1/100sFireworks ~1-2sAirshow ~1/1000s

Shutter Speed Examples

ISO

The ISO number is how sensitive the sensor is to light. The higher the ISO, the higher the sensitivity

Tradeoff – Degrades image by grainy noise and reduces color accuracy

Max ISO without significant degradationNew Pro DSLRs – ISO 3200Prosumer – ISO 800P&S – ISO 400

Noise and Color Degradation

The “Right” Exposure Camera ‘meters’ the scene and decides what is best Given the shutter, aperture, and ISO settings are versus what the

camera thinks, the light meter reflects an over or under exposure in ‘stops’

A stop of light is either half or double that of the adjacent stop (if 0 is 1/60th at F2.8 and ISO 200, +1 overexposure could be 1/30th at F2.8 and ISO 200)

0 +1 +2 +3-1-2-3

Capturing Light with a Camera

Dark Bright

Direct SunBright Room18% GreyShaded AreaSomething Black

How much your camera can capture

~10 stops of light

• The camera judges ‘proper exposure’ by putting as much of the scene as possible withinthat limited area

• Often times it cuts off things too bright or too dark• Understand what your camera took through your histogram

Increase Exposure to capture

Decrease Exposure to capture

Histogram Shows how the

captured light is distributed

Left side is dark Right side is bright If it’s off of the

histogram, data is lost

Control by exposure compensation or manually adjusting exposure

Histogram Special Case - Backlight

QUESTIONS?