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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?