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Exposure. Photography Basics. 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
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Exposure Photography Basics 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 Large Aperture, Low F-stop Shallow Depth of Field Aperture/ F-stop The amount of light captured Small Aperture, High F-stop Large Depth of Field Freezes Action Low “Noise” Fast Shutter Speed Low ISO Slow Shutter Speed High ISO Motion Blur Sensor Sensitivity (ISO) Shutter Speed High “Noise”
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 2/3 Focal Point 1/3
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 ~ 1/60s • Jogging/Dance ~ 1/100s • Fireworks ~1-2s • Airshow ~1/1000s
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 degradation • New Pro DSLRs – ISO 3200 • Prosumer– ISO 800 • P&S – ISO 400
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) -3 -2 -1 0 +1 +2 +3
Capturing Light with a Camera Increase Exposure to capture Decrease Exposure to capture How much your camera can capture ~10 stops of light Dark Bright Something Black Shaded Area 18% Grey Bright Room Direct Sun • The camera judges ‘proper exposure’ by putting as much of the scene as possible within • that limited area • Often times it cuts off things too bright or too dark • Understand what your camera took through your histogram
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