1. Exposure Alan Louie Jul 2010

2. Overview  Controls of your camera  The Trinity of Light ISO, Shutter Speed, Aperture  Getting the right exposure The Histogram

3. 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

4. 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 Speed Low ISO High ISO Sensor Sensitivity (ISO) Freezes Action Motion Blur High “Noise” Low “Noise” Large Depth of Field Shallow Depth of Field

5. 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

6. Depth of Field Examples

7. 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

8. Shutter Speed Examples

9. 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

10. Noise and Color Degradation

11. 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 1/60 th at F2.8 and ISO 200, +1 overexposure could be 1/30 th at F2.8 and ISO 200) 0+1+2+3-2-3

12. 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 within that 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

13. 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

14. Histogram Special Case - Backlight