Choosing a Camera
Taking Good Pictures
Digital Photography Advice
HDR Part 1
HDR Part 2
HDR Part 3 Hellyer Park
HDR Part 4 Uvas Canyon
Santa Teresa Pueblo HDR Sunset
HDR Sunset Norred Trail
Bay Area Back Pages
Bay Area Biking
SF Bay Area Rec. & Travel Home
Bay Area Parks
chemical on plastic backing that records image in film camera
electronic light-sensitive chip that records image
of camera that focuses light on the film/sensor
mechanical or electrical control of how long the film/sensor is exposed
letting light onto the film/sensor to capture an image
range or dynamic
range: range of lighting in a scene, from the brightest to the
a sharp image on the film/sensor by adjusting the lens
of focus: range of depth over which objects are in focus.
optical or electronic means of viewing the scene in the camera before
taking the picture
- Sensitivity of film/sensor to light.
- Specified as ASA/ISO number
- Slow: ASA/ISO 100 and lower for daylight
- Medium: ASA/ISO 200, general purpose
- Medium-fast: ASA/ISO 400: indoors
- Fast: ASA/ISO 800 and above: low-light, sports, action
- Higher speed = more sensitive, more grainy, wider dynamic
range, lower contrast
- Film is made in different speeds
- Sensor: adjusts speed electronically. Higher speed = more
- Color or black and white negative, used
mainly for making prints
- Color or black and white transparency (positive, reversal film),
used for direct viewing as slides
produces finished print in seconds after exposure, very expensive per
shot, discontinued by Polaroid, still made by Fujifilm.
- Sensors convert light into electricity
- Sensors are a matrix of light-sensitive elements
- Smallest sensing unit is the pixel
- Resolution is measured in megapixels (million pixels)
- Types of sensors:
reduction: SLR sensors are exposed to dust when lenses are changed.
Automatic dust removal vibrates the sensor or filter in front of sensor
to shake off dust.
size measured in width (35 mm), dimensions (4”X5”) or type
- Larger film = higher resolution, bigger camera, higher
- Digital equivalent is sensor size. Sensors are usually
- Common digital sensor
sizes: full-frame (24X36 mm), APS-C, 4/3", 1/2",
- Larger sensors = lower low-light noise
- Smaller sensors mean deeper depth of field
factor: ratio of full-frame 35 mm to sensor width,
multiplies effect of focal length of lens
- Color balance varies with lighting: outdoor (lots of
(lots of red), indoor fluorescent lighting (lots of green)
- Electronic flash simulates outdoor lighting
- Film is made for specific lighting conditions, specified
temperature in degrees Kelvin.
- Filters can be used to adjust for different lighting, but
- Digital cameras can adjust color balance automatically or
can be selected manually
- Color balance can be adjusted by photo editors
- Exposure range:
latitude: range of a film's ability to capture the brightest to
darkest areas of a subject and still maintain detail, also how much
film can be over or under-exposed and still have acceptable results.
- Faster film (higher ASA/ISO) tends to have wider latitude.
- Color negative films has wider latitude than transparency
- Digital equivalent is sensor dynamic range.
- Larger pixels in digital sensors have wider dynamic range.
- Special sensor design can increase dynamic range, e.g. Fuji Super CCD
- Film Form
Camera Storage Media
early format, now obsolete, max capacity 128 MB.
Flash: largest size, highest capacity, popular in DSLR's.
- Multimedia Card (MMC): predecessor of SD.
- Secure Digital
(SD): most popular format for compact cameras, mini-SD and micro-SD
are smaller versions.
Stick: proprietary format from Sony.
Picture Card: proprietary format used by Olympus and Fujifilm
1 inch hard disk drives in compact flash format, now largely superceded
by flash memory.
disk: 1.4 MB magnetic diskette, used in early digital cameras, now
writeable compact disks, used in early digital cameras, max capacity
writeable DVD disks, used in digital video cameras, capacity ~4.7 GB.
Lens Focal Length
from lens to focal point (where distant light entering lens converges
- Larger focal length = higher magnification
- Smaller focal length = wider field of view
- Larger focal length = longer lens
lenses have a fixed focal length
- Zoom lenses
have variable focal length. Zoom range = ratio between longest and
shortest focal length, not the maximum magnification.
can be used to increase the focal length of existing lenses, at the
expense of lens speed.
- Wideangle converter can be used to decrease the focal
length of existing lenses.
lens gives extremely wide angle, but with extreme distortion
lens allows extreme close-ups
- Close-up lens decreases minimum focusing distance of
- Extension tubes/bellows decreases focusing distance of
- For 35 mm:
- 50 mm is “normal” (what your
eye would see)
- <50 mm is wide angle,
good for landscapes
- >50 mm is telephoto
- Magnification is focal length / 50, e.g. 100 mm is 2X,
200 mm is 4X
- 80-100 mm is medium telephoto, good for portraits
- 135-250 mm is long telephoto, good for sports
- 300+ is super telephoto, good for wildlife
- Very long focal length lenses can use mirrors, like a
- Longer focal lengths means bigger, longer, heavier,
more expensive lens.
- Lenses for digital cameras are often specified with 35 mm
equivalent focal lengths.
- Magnification depends on film/sensor size, larger
for same magnification
opening (usually controlled by variable-size iris)
- Specified as f-stop (focal length divided by lens opening
- Lower f-stop number = wider lens opening, more light let in
to film/sensor, shallower depth
- Higher f-stop number = smaller lens opening, less light let
in to film/sensor, deeper depth
- Standard f-stops: f/1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22
- Each successive f-stop step cuts the light by half
- Lower f-stop requires bigger, heavier, more expensive lens
- Film cameras use mechanical shutters.
- Digital cameras can use either electronic or mechanical
shutters, or both.
how long shutter exposes film to light
- Measured in fractions of a second, only denominator
specified (100 =
- Set shutter speed to stop action, prevent motion blur
- Faster subject motion requires faster shutter speed
- Faster shutter speed requires faster film, wider aperture
- Longer focal length lens requires faster shutter speed to
- With normal lens, use 1/125th second for hand-held shots.
- Image stabilization allows slower shutter speeds.
focus: cheapest, lens with small aperture has enough depth of
so no focusing is necessary, usually used in cellphone cameras.
line up split image in viewfinder, linked to lens
- Through-the-lens manual: see image through the lens, adjust
image looks sharp (used in Single-Lens
Reflex = SLR, twin-lens
and view camera)
electronically focuses using:
used mostly in point-and-shoot film cameras, emits 2
beams to illuminate subject to determine distance, works in darkness,
not focus through windows, has limited range.
used mostly in Polaroid instant cameras,
off subject like sonar to determine distance, works in darkness, will
focus through windows, has limited range, transducer is big.
sensing: used mostly in digital cameras, computer determines focus
by adjusting focus until image contrast is maximized, does not work in
dark (unless camera has focus assist light) or on featureless object,
can focus through windows.
detection: used in SLRs, passes light through separate paths
and detects when they are in phase, does not work in the dark (unless
camera has focus assist light) or on featureless
object, can focus through windows.
- Auto-focus Zone: part of the image that the auto-focus
focuses on, usually the center of the picture.
- Feature recognition: camera's computer analyzes the image,
looks for features to focus on (e.g. face-recognition).
Lock: freezing the focus on the image in the auto-focus zone,
usually by depressing the shutter release halfway, also can lock
- Proper exposure
- Amount of light on the subject
- Light reflected from the subject
- Film/sensor speed
- Shutter speed
In daylight, with aperture at f/16, shutter speed is 1/ISO number. For
with ISO 100 film, set shutter speed to 1/100th sec. Slight overcast:
f/11, overcast (slight shadows): f/8, heavy overcast: f/5.6.
- Fixed exposure (usually in disposable film cameras):
shutter speed and
aperture are fixed, camera uses fast film and small aperture to work in
wide exposure range.
- Full manual: set aperture and shutter speed manually, no
metering (use exposure tables, separate light meter)
light meter: adjust aperture/shutter until
you set aperture, camera sets shutter speed
priority: you set shutter speed, camera sets aperture
camera picks best combination of aperture and shutter
modes: exposure pre-programmed for specific scenes,
e.g. fireworks, portraits, sports, landscapes, snow/sand, sunset, etc.
- Digital camera can also adjust sensor speed
separate light meter, often used by pros
- External: light sensor on outside body of camera, usually
on inexpensive film cameras
- Through-the-Lens (TTL): internal light sensor measures
light through the main lens, used in SLRs, digital cameras
- Average metering: measures light over the whole image
area, used by external sensors and handheld meters.
- Spot metering: measures light only from a small area
- Center-weighted average metering: Measures light from a
wide area of the image, but mainly from the center.
- Matrix/multi-metering: measures light from multiple areas
and calculates the correct exposure.
- Face detection: digital camera's computer recognizes
faces, adjusts exposure for the face
- Exposure tradeoffs:
- Wider aperture (lower f-stop) = more exposure
- Wider aperture = shallower depth of field
- Shutter speed
- Slower shutter speed = more exposure
- Slower shutter speed = more motion blur
- Film/sensor speed
- Faster speed = more exposure
- Faster speed = more grain/noise
- Also called vibration reduction, blur reduction, anti-shake
- Reduces image blur from hand-holding camera at slow shutter
- Sensors detect and measure camera motion
image stabilization shifts a lens element to compensate for camera
motion, built into lens, works with film and digital cameras
- Sensor shift stabilization shifts the image sensor to
compensate for camera motion, works with any lens, for digital cameras
- Can improve speed by 2-4 stops
- Digital image stabilization, electronic vibration
reduction, anti-blur increases the sensor sensitivity to allow using a
higher shutter speed, at the expense of higher noise
by Ronald Horii 9/14/05, revised 5/26/10