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Camera orientation / Basic metering - IVY Tech
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Camera orientation / Basic metering - IVY Tech

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Camera orientation / Basic metering - IVY Tech Camera orientation / Basic metering - IVY Tech Presentation Transcript

  • Camera orientation & basic metering
  • How does a camera work?
  • Camera obscura You don't need a camera to make an image, just a light-tight box and a hole to let the light in – http://youtu.be/gvzpu0Q9RTU View slide
  • Exposure
    • Refers to the amount of light that falls on photographic film, or a digital CCD
    Determined by 3 things
    • The size of the opening (aperture) the light passes through
    • The length of time the film or CCD receives the light (shutter speed)
    • The film or CCD's sensitivity to light (ISO)
    View slide
  • Aperture (or F stop)
    • Refers to the change in the diameter of the lens opening, to let in more light (wide opening) or less light (narrow opening) through the lens.
  • Aperture (F Stop) scale
    • The F Stop number is the bottom half of a fraction
    • When the lens is set to f2, the opening in the lens is 1/2 as big as the lens is long.
    • When the lens is set to f8, the opening in the lens is 1/8th as big as the lens is long.
    • Which opening is bigger, 1/2 or 1/8?
    • Which f-stop lets in more light, f2 or f8?
    • A smaller number lets in more light
    • Each f-stop lets in half as much light as the previous stop
    Aperture (F Stop) scale
  • Aperture also determines the Depth of Field , or the amount of focus in a photo, from foreground to background.
  • Use a low number (f5) for a short depth of field
  • Use a high number (f32) for a wide depth of field
  • Exercise: Depth of Field Image Sorter http://www.christykarpinski.com/toolkit/
  • Shutter Speed The length of time the camera shutter is open to let the light in the camera. The times vary from tiny fraction of a second (1/2000) to several seconds or longer.
  • Shutter Speed scale
    • The shutter speed number is the bottom half of a fraction
    • When the shutter speed is set to 125, light comes in for 1/125th of a second.
    • When the shutter speed is set to 8, light comes in for 1/8th of a second.
  • Shutter Speed scale
    • Which is longer, 1/125th or 1/8th?
    • Which shutter speed lets in more light, 8 or 125?
    • A smaller number lets in more light
    • Each number lets in half as much light as the previous stop 1 1/2 1/4 1/8 1/15 1/30 1/60 1/125 1/250 1/500 1/1000
  • Shutter Speed is used to freeze action or cause blur
  • Shutter Speed is used to freeze action or cause blur
  • Exercise: Shutter Speed Image Sorter http://www.christykarpinski.com/toolkit/
  • Equivalent Exposures For every photograph, there are a number of aperture/shutter speed combinations that allow exactly the same amount of light to strike the camera’s CCD, resulting in exactly the same amount of exposure. These are called EQUIVALENT EXPOSURES.
    • Indicates the camera's sensitivity to light
    • The ISO scale for the a typical digital camera is: 100 - 160 - 200 - 400 - 800 - 1600 - 3200
    • The higher the ISO number the more sensitive your camera is to light.
    • Use a high ISO if you want to shoot in low light
    • Every time an ISO doubles or halves it is a change of 1 STOP
    • Therefore ISO 400 is 1 stop more light sensitive than ISO 200
    ISO
  • ISO settings determine the amount of digital 'noise' High ISO settings (left) allow you to shoot in low light, but create digital noise.
  • For the best quality image, always use the lowest ISO that will give you enough exposure for a good picture in your lighting conditions.
  • Preset exposure modes: Auto, Program or Scene
    • Safest bet if you don't want to customize your shot
    • Picks the best exposure combination for the mode you select (landscape, macro, portrait etc)
    • Does not allow any customization of your image
  • Portrait mode
    • Uses a large aperture (small number) which helps to keep your background out of focus (ie it sets a narrow depth of field – ensuring your subject is the only thing in focus and is therefore the centre of attention in the shot).
    • Portrait mode works best when you’re photographing a single subject so get in close to your subject
  • Macro mode
    • Used to take a close up picture (flowers, insects, etc).
    • Focussing is more difficult as at short distances the depth of field is very narrow (just millimeters at times).
    • Keep your camera and the object you’re photographing parallel if possible or you’ll find a lot of it will be out of focus.
    • Use a tripod
  • Landscape mode
    • Uses a small aperture (large number) to make sure as much of the scene you’re photographing will be in focus as possible (ie it give you a large depth of field).
    • At times your camera might also select a slower shutter speed in this mode (to compensate for the small aperture) so you might need to use a tripod.
  • Sports mode
    • Uses a fast shutter speed to freeze action
    • Try panning your camera along with the subject and/or attempt to pre-focus your camera on a spot where the subject will be when you want to photograph it (takes practice).
  • Aperture priority mode
    • You select the aperture, the camera chooses the shutter speed to create a good exposure
    • Use this if you want to control the depth of field
    • What F Stop would you use for a wide depth of field?
    • F16 or 22
    • What F Stop would you use for a narrow depth of field?
    • F4 or 5.6
  • Shutter priority mode
    • You select the shutter speed, the camera chooses the F Stop to create a good exposure
    • Use this if you want to blur or freeze motion
    • What shutter speed would you use to blur motion?
    • 1/60 or less
    • What shutter speed would you use to freeze motion?
    • 1/250 or higher
    • MANUAL: You set the ISO number.
    • AUTO: The camera sets the ISO mode that will give you the best image under your lighting conditions.
    • Not all digital cameras have a manual ISO mode; many point & shoot cameras have fully automatic ISO settings only.
    Exposure modes: ISO
  • How cameras measure light
  • A camera’s internal reflective light meter is designed to give good exposure results when pointed at a scene with typical — more or less even—distributions of light and dark tonal values, like the scene below.
  • The tonal values in a typical, well-exposed scene, when averaged together, will form a single MIDDLE-GREY value. Middle Grey* This value is also known a s 18% GREY because it reflects 18% of the light that strikes it when it is reproduced on printed matter.
  • Your camera’s light meter sees the scene only as a single gray tonal value, which it compares to the averaged tonal distribution of a typical scene, middle grey. Middle Grey How a light meter sees any scene—as a single grey value
  • Since most scenes have a typical distribution of light and dark values, you can point your camera at most scenes in general and get good exposure results.
  • Middle Grey Your camera light meter will see a typical scene which is overexposed as a grey tonal value which is lighter than middle grey. It will decrease exposure to correct this, until the scene is a middle grey.
  • Your light meter will see a tonally typical scene which is underexposed as grey tonal value which is darker than middle grey. It will correct by increasing exposure – lightening the tonal value—until it is middle grey. Exposure Corrected to Middle Grey Middle Grey
  • If you have a manual exposure setting on your camera, you can use a grey card to set your exposure for a scene. http://tinyurl.com/3ehsksl Taking a grey card reading
  • Center -weighted averaging metering mode: meters entire scene, most heavily in the center. Multi-pattern metering mode: Measures brightness over several independent segments across the screen. Useful when you have a range of darks and lights. Spot (averaging) metering mode: for metering a very small area of the scene. Exposure metering modes
  • Bracketing
    • Shooting a scene at normal exposure, then taking extra shots which are overexposed and/or underexposed in order to record a range of exposures.
  • Normal F/4 +1 Stop F/2.8 -1 Stop F/5.6
  • 3 ways to achieve bracketing
    • Some cameras have AUTOMATIC BRACKETING which allows the user to program the camera to automatically bracket by up to 5 stops, usually in 1/3 or ½ stop increments (depending on the camera model) over 2 or more exposures.
    • Bracketing can also be done manually, using your camera’s EXPOSURE COMPENSATION control.
    • Bracketing can be achieved in Manual exposure mode by adjusting your camera’s aperture and/or shutter speed to overexpose or underexpose
  • Your camera’s exposure compensation control allows you to underexpose (darken) or overexpose (lighten) your image in stops to insure proper exposure, or for creative control. Typical Exposure Compensation camera icon Exposure Compensation
    • A typical digital camera Exposure Compensation display may look similar to this.
    • EV stands for exposure value. Exposure values are measured in stops.
    • This camera display indicates that exposure compensation can be adjusted in ½ stop increments. Many digital cameras also can be adjusted in 1/3 stop increments.
  • Dynamic Range The camera cannot record the same range (dynamic range) of lights and darks that we see with our eyes. For example, we can see details in a scene outside and inside a window. But a camera cannot display both of these, therefore we have to choose to portray one or the other. This is the camera's limitation.
  • Dynamic Range Photo exposed using aperture-priority mode, no exposure compensation
  • Dynamic Range Photo exposed using aperture-priority mode, 2 stops exposure compensation
  • Your digital camera’s White Balance settings adjust your camera so that it reproduces natural looking color in most lighting situations. DAYLIGHT FLUORESCENT TUNGSTEN OPEN SHADE OVERCAST SKIES AUTOMATIC WB CUSTOM WB FLASH
  • Natural daylight is white. Your digital camera’s Daylight White Balance setting adjusts your camera so that it reproduces color accurately in daylight and all other lighting conditions.
  • Daylight
    • However, if you shoot under lights that are not white, you will see a color cast in your digital photographs.
      • Tungsten light, for instance, has a red-orange-yellow cast.
      • Fluorescent lights may have a yellow, green, blue, or magenta cast.
  • Daylight white balance setting shows blue cast LIGHT SOURCE: FLUORESCENT LIGHTS
  • Fluorescent white balance setting corrects blue color cast LIGHT SOURCE: FLUORESCENT LIGHTS
  • Daylight white balance setting shows yellow cast LIGHT SOURCE: TUNGSTEN
  • TUNGSTEN white balance setting: Corrects yellow cast LIGHT SOURCE: TUNGSTEN
  • LIGHTING CONDITIONS: OPEN SHADE Shadows in open shade are blue because the light source is the blue sky.
  • Open shade WB setting corrects blue color cast. LIGHTING CONDITION: OPEN SHADE
  • Overcast skies give scene slightly green color cast LIGHTING CONDITIONS: Overcast Skies
  • “ Overcast” WB camera setting corrects green color cast LIGHTING CONDITIONS: Overcast Skies
  • For shooting in most lighting conditions—even mixed—for instance, tungsten with daylight coming in windows. Usually does good job. Good for general shooting. LIGHTING CONDITIONS: ANY
  • CUSTOM WHITE BALANCE: Produces more precise color corrections based on white card reading, than other WB settings. LIGHTING CONDITIONS: ANY
    • AF-S (S: Single-AF servo)
    • AF-C (C: Continuous-AF servo)
    • MF (M: Manual focus)
    FOCUS MODES Allow users to select HOW the camera focuses
  • AF-S (S: Single-AF servo)
  • AF-C (C: Continuous-AF servo)
  • MF (M: Manual focus)
    • AF AREA MODES
    • Allow the user to change the focusing method used for automatic
    • focusing (when the focusing mode is set to S-AF or C-AF. )
    • These settings generally determine WHERE in the scene the camera
    • will automatically focus using focus areas.
    • In this example, AF focus areas are
    • Indicated by “+” symbols.
    • You may choose one of these areas
    • as an autofocus point, or let the
    • camera choose automatically.
    • Your camera may use some other
    • symbol or icon to indicate AF areas.
    • Check your manual.
  • AF Area Modes
  • Single-Frame: One shot is taken each time you press the shutter release. Use this mode to take a single clearly defined shot in each frame. Continuous Shooting: This mode allows you to take consecutive shots by holding down the shutter release. (Generally cannot be used with built-in flash. Self-timer Mode: Sets the camera to delay exposure for a preset period after you press the shutter release. Use when you want to be in the photograph, or to reduce camera shake. Use a tripod or place the camera on a stable surface before using the self-timer.