Transcript Chapter Six - Lingnan University

Chapter Six
Digital Photography Foundations
(How to use the various settings
on your digital camera)
Image Size
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Large, medium, small, etc.
Choose whatever the largest image
size gives you
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the most flexibility (enlarging, cropping,
high-quality printing, etc.)
Drawback: large image sizes mean less
taking images on the same memory card
Comment: memory cards are getting
cheaper all the time; get a spare one if
necessary
3:2
7,360 x 4,912 (L),
5,520 x 3,680 (M),
3,680 x 2,456 (S)
6,144 x 4,080 (L),
4,608 x 3,056 (M),
3,072 x 2,040 (S)
4,800 x 3,200 (L),
3,600 x 2,400 (M),
2,400 x 1,600 (S)
5:4
6,144 x 4,912 (L),
4,608 x 3,680 (M),
3,072 x 2,456 (S)
Compression: JPEG
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JPEG compression is lossy
The less compression, the higher the image
quality
The higher compression, the smaller the
image file size
Many digital cameras allow you to set the
levels of compression
RAW file format has no compression
JPEG Quality
ISO setting
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Typical settings: 50,100, 200, 400, 800, 1600,
3200
Auto ISO: the camera chooses an ISO value
depending on lighting conditions, e.g. welllighted scenes 100-200, dark scenes 8001600
High ISO settings (e.g. 1600 or above) tend
to cause noise in images
ISO setting tips
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For well-lighted “normal” shots, use 100-200
for best image quality
For “action” shots, use 400 or 800 for faster
shutter speed
For indoor or night shots without flash, use
1600 or above
Color Temperature
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Light sources
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2000K Sunrise
2500K Light bulbs
5000-5500K Daylight, flash
9000K Overcast sky
Lower color temperature means “warmer”
color (reddish)
Higher color temperature means “cooler”
color (bluish)
White Balance (WB)
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A piece of white paper would look pure white under
broad day light.
A piece of white paper would look a little bit blue
under fluorescent light.
We would “see” a white paper in both cases
because our brains (not our eyes) already “adjust”
the color in real time.
An image sensor would “honestly” record the slightly
blue color in the second case.
It is up to the camera’s CPU to “adjust” the color of
the image to compensate for the non-white light
source.
http://www.photoxels.com/tutorial_white-balance.html
Auto White Balance (AWB)
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The camera evaluates the scene and tries to
determine the white point(s) of the scene.
Not always successful, e.g. when bright
colors fill most of the scene, or in low
temperature lighting.
Presets and custom WB
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Daylight, cloudy, tungsten,
fluorescent, flash, etc.
Best to take test shots to determine
the most appropriate presets.
Most digital cameras allow you to manually
set a custom WB for a particular lighting
condition by taking a shot of a white subject
under that condition.
Some digital cameras even allow you to set
WB in terms of color temperature, e.g. 5000K
Sharpening
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Most digital cameras use in-camera
sharpening to compensate for color
interpolation.
In-camera sharpening of images may not
give the most desirable results as sharpening
could remove useful details of an image.
Some cameras allow you to set different
levels of sharpening or even disable
sharpening.
Color Spaces
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A color space determines
how many different colors
can be recorded on a digital
camera.
The most commonly used
color space: sRGB
Some digital cameras
provide other color spaces
which are usually richer than
sRGB, e.g. Adobe RGB
Exposure
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Correct exposure depends on:
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Amount of light hits the sensor (aperture)
Exposure time (shutter)
Sensitivity of the sensor (ISO)
Most digital cameras have good built-in
exposure meters to help set the correct
combinations of the above.
Aperture
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Eg. f2, f2.8, f4, f5.6, f8, f11, f16, f22, etc.
f-stop = Focal length / diameter of aperture
The bigger the aperture, the more light
passing through
Aperture affects depth of field
f-stop video
Video on depth of field
Shutter speed
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1/1000, 1/500, 1/250, 1/125, 1/60, 1/30, …
Longer exposure allows more light to hit the
sensor.
Reciprocity
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Increasing the shutter speed (freezes
movement) can be compensated by widening
the aperture (less depth of field).
Similarly, decreasing the shutter speed
(longer exposure) can be compensated by
reducing the aperture (more depth of field).
Full Auto Mode
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Fully automatic
Evaluates lighting
Select ISO, white balance, aperture, shutter
speed, flash, etc.
Program (P) Mode
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Similar to Auto mode
Allow setting ISO, WB, exposure
compensation
Allow choosing aperture-shutter reciprocal
combinations.
Program Exposure
Canon Powershot G6
Very similar to AUTO exposure but you have access to all the normal manual
controls, can set the ISO, exposure compensation, use AE lock, bracketing etc. The
G6 has program shift, activate shift by pressing the * (AE/FE-Lock) button, then
turn the main dial to select from various equivalent exposures.
Example (pressing * metered 1/50 sec, F4.0):
• 1/30 sec, F4.5 (turn left)
• 1/40 sec, F4.0 (turn left)
• 1/50 sec, F4.0 (metered)
• 1/60 sec, F3.5 (turn right)
• 1/80 sec, F3.2 (turn right)
Aperture Priority (A) Mode
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Preset aperture (by you)
Camera adjusts shutter speed based on
lighting
Give better control to depth of field (wider
aperture for less DOF, and vice-versa).
Tip: for portraits, you may set a wider
aperture to “blur” the subject’s background
Tip: for landscape, you may set a smaller
aperture to make the whole scene clear
Shutter Priority (S/T) Mode
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Preset shutter speed (by you)
Camera adjusts the aperture
based on lighting
Tip: fast shutter speed for
capturing motion, also avoid
“motion blur” due to hand shake
Tip: slow shutter for “creative”
blur
Manual (M) Mode
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You may set any combination of aperture and
shutter speed and other settings (e.g. ISO).
Useful for night and studio photography
Scene Modes
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Portrait
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Night portrait
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“blur the background” through large
aperture and center-weighted metering
Slow shutter speed to “see enough light”
of the background and flash for the
foreground subject
Landscape
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Small aperture for deep depth of field
More sharpening, contrast, and saturation
Scene Modes (cont.)
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Night Landscape
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Beach/Snow and Backlight
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Slow shutter speed, no flash
Compensate for overly bright
reflections and backgrounds
Close-Up/Macro
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Longest zoom and fast enough
shutter speed (to avoid “hand
shake” blur)
Scene Modes (cont.)
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Sports
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Black and White/Monochrome
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Relatively fast shutter speed to freeze
actions
Continuous shooting
Capture grayscale images
Other modes
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E.g. fireworks, pets, food
Metadata (EXIF)
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Records of exposure settings (e.g. ISO,
aperture, shutter speed, etc.)
Accessible through software
Depth of Field in
Compact Digital Cameras
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Deeper depth of field is achieved by:
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Smaller aperture
Shorter focal length
Greater subject distance
Compact digital cameras tend to have
smaller image sensors and lenses with
shorter focal lengths
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Hence, they tend to give deeper depths of field
than compact film cameras.
Exposure Latitude
of Image Sensors
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Also called dynamic range
Similar to that of slide films
More susceptible to overexposure
Overexposed areas of an image become
“pure white” with no details
Tip: use downward exposure compensation
to “save” potentially overexposed details