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  2. 2. UNDERSTANDING EXPOSURE Exposure is one of the most critical elements of Photography. There are three adjustable elements that control the exposure: ISO, Aperture and Shutter Speed.
  3. 3. (4) ISO The measure of a digital camera sensor’s sensitivity to light (5) Shutter Speed The amount of time that the shutter is open (11) Aperture The size of the opening in the lens when a picture is taken
  5. 5. SHUTTER SPEED • Controls the speed at which the shutter opens and closes • The shutter blocks all light from exposing the film UNTIL you press the button. Then it quickly opens and closes, giving the film a brief flash of light. • You can control the length of time the shutter remains open by setting the SHUTTER SPEED. • It determines how long the shutter stays open. • The longer exposures ( like 1 second ) give much more light to the film than a 1/1000 of a second exposure. So even though the number may look bigger, don't be deceived! Longer shutter speeds = more light Shorter shutter speeds = less light
  6. 6. WHAT SHUTTER SPEED TO USE • A standard shutter speed is 1/125 or 1/250 of a second – these speeds are appropriate for a normally lit outdoor shoot. • Bright, sunny day/ excessive light – use a faster speed such as1/500 • Overcast or late afternoon – a slower speed should be used, such as 1/60 • A shutter speed slower than 1/60 of a second should only be used with a tripod
  9. 9. SHUTTER SPEED Small group task: In small groups complete activity: 1a 1b 3 of your textbook – Page 16
  10. 10. APERTURE • Before light reaches film, it must pass through an opening called an "Aperture". • Like the pupil in a human eye, the aperture on a camera controls light. It does so by closing up to restrict light, and opening up to let it through. Smaller F-stop number = larger opening Larger openings = more light
  11. 11. APERTURE • The f stop number indicates a fraction of the hole’s size in relation to the focal length of the lens • Each f stop allows half as much light as the f stop before it The larger the f stop number, the smaller the hole in the lens
  12. 12. WHAT APERTURE TO USE • A standard aperture is around f.8 or f.11 DEPTH OF FIELD • The eastist way to understadn how to control the zone of focus in a photograph is to remember the following: • Large f stop number (for example, f.22) = large DOF • Small f stop number (for example, f.4) = small DOF
  13. 13. LIST OF F.STOPS
  14. 14. ISO (INTERNATIONAL ORGANISATION FOR STANDARDISATION ) • Is the sensitivity of the film or imaging sensor to light • The ISO is often referred to as ‘light speed’ • The faster the film speed, the higher the sensitivity of the film to light • The higher the number, the higher the degree to sensitivity High ISO = Poor lighting conditions (for example indoors without a flash)
  15. 15. SITUATIONS - ISO Situations where you might need to push ISO to higher settings include: • Indoor Sports Events – where your subject is moving fast yet you may have limited light available. • Concerts – also low in light and often ‘no-flash’ zones • Art Galleries, Churches etc- many galleries have rules against using a flash and of course being indoors are not well lit. • Birthday Parties – blowing out the candles in a dark room can give you a nice moody shot which would be ruined by a bright flash. Increasing the ISO can help capture the scene.
  16. 16. A METAPHOR FOR EXPOSURE Imagine your camera is like a window with shutters that open and close. Aperture is the size of the window. If it’s bigger more light gets through and the room is brighter. Shutter Speed is the amount of time that the shutters of the window are open. The longer you leave them open the more that comes in. Now imagine that you’re inside the room and are wearing sunglasses (hopefully this isn’t too much of a stretch). Your eyes become desensitized to the light that comes in (it’s like a low ISO). There are a number of ways of increasing the amount of light in the room (or at least how much it seems that there is. You could increase the time that the shutters are open (decrease shutter speed), you could increase the size of the window (increase aperture) or you could take off your sunglasses (make the ISO larger).
  17. 17. A METAPHOR FOR EXPOSURE Achieving the correct exposure is a lot like collecting rain in a bucket. While the rate of rainfall is uncontrollable, three factors remain under your control: the bucket's width, the duration you leave it in the rain, and the quantity of rain you want to collect. You just need to ensure you don't collect too little ("underexposed"), but that you also don't collect too much ("overexposed"). The key is that there are many different combinations of width, time and quantity that will achieve this. For example, for the same quantity of water, you can get away with less time in the rain if you pick a bucket that's really wide. Alternatively, for the same duration left in the rain, a really narrow bucket can be used as long as you plan on getting by with less water. In photography, the exposure settings of aperture, shutter speed and ISO speed are analogous to the width, time and quantity discussed above. Furthermore, just as the rate of rainfall was beyond your control above, so too is natural light for a photographer.
  18. 18. RESOURCES Exposure Guide http://www.exposureguide.com/exposure.htm Photography Guide http://digital-photography-school.com Camera Stimulator http://www.kamerasimulator.se/eng/?page_id=2 Other http://www.photonhead.com/beginners/shutterandaperture.php http://www.cambridgeincolour.com/tutorials/camera-exposure.htm