Exposure for Elementary Photo基本的照片曝光.ppt

Exposure for Elementary Photography,Exposure,To get a rich image with realistic tones, dark but detailed shadows, bright, delicate highlights, and vibrant colors you need to expose correctly.,Exposure,Chose a combination of aperture and shutter speed settings to allow the right amount of light for each scene.,Exposure,The best prints result from properly exposed digital files and negatives.,Exposure,The purpose of correct exposure is to get just the right amount of light onto the capture sensor or film frame.,Exposure,A correctly exposed image is somewhat like a full glass of water.,Water running slowly will take a relatively long time to fill the glass.,Water turned to full blast will take a relatively short time to fill a glass,Correct Exposure,Whether the exposure is made (the glass is filled ) slowly or quickly with a fast or slow exposure time, or through a small or large opening, the goal is the same: to get a properly exposed, but not overexposed, image (full glass of water).,Correct exposure using digital capture,A correct exposure on negative film,4 Variables that influence Exposure,. Amount of light on the subject . Aperture or F stop selection . Shutter speed selection . ISO Sensitivity of the camera selection or film speed,1. Amount of light on the subject,Bright day at the beach or on snow Sunny clear day Cloudy Day, fog, rain Dusk or Dawn Inside,Night,2. Aperture,Size of the opening of a lens determined by the position of the aperture blades-opening up to a larger circle, or closing down Controls the volume of light Measured in f-stop numbers,Aperture,f-Stops Expressed as a number Mathematical fraction Aperture Space created by opening or closing down: Diaphragm or aperture blades Metal pieces which create the Aperture,The Aperture Controls, Exposure, Depth of Field,3. Shutter Speed,Setting on the camera or lens that determines how long the shutter is open allowing light to strike the capture sensor or film. Shutter can be a focal plane or leaf type SLR focal plane shutters may travel horizontally or vertically.,Shutter Speeds Control,Exposure Motion,4. ISO/Sensitivity,International Standards Organization The sensitivity of the film or digital camera setting (100, 200, 400, 800, etc) Expressed as a number that is measured in stops,Exposure,How can we measure the light to determine? How to set the f-stop & Shutter speed? How do we chose sensitivity settings or film speed?,Meters,Reflected In your 35mm camera Reads the light reflected from your subject Incident Hand held meter Reads light falling on the subject,Stops of Light,All variables that control the amount of exposure can be measured in units called stops. Meters measure the amount of light in a scene in stops. Aperture, shutter speeds, film or chip sensitivity are all expressed in stops,