Digital Photography
Part 3
Creative control
What are creative controls?
The key factors that decide how a composition will
look:
• focusing
• white balance
• shutter speed
• aperture
• focal length
Cameras can set these automatically (except focal
length), but learning how to use them manually helps
in getting great pictures.
Péter Tarján
2
Shutter speed
Shutter speed is one of the 2 factors
that determine exposure. Shutter
speed is the time interval during
which the shutter is open and the
sensor is getting light. For every
full stop, the amount of light on
the sensor is (about)
doubled/halved.
Reasons to set shutter speed
manually:
• avoid camera shake
• freeze movement
• blur movement
• panning
• increase/reduce depth of field
The standard shutter speeds:
…
4 sec
2 sec
1 sec
1/2 sec
1/4 sec
1/8 sec
1/15 sec
Péter Tarján
1/30 sec
1/60 sec
1/125 sec
1/250 sec
1/500 sec
1/1000 sec
1/2000 sec
…
3
Effect of shutter speed
Péter Tarján
4
Steady shooting
When shutter speed is low, camera
shake may blur the image. Its effect
can be greatly reduced by holding
the camera correctly.
Hold the camera firmly with both
hands. Stand with your feet slightly
apart. Hold your elbows close to
your body. Squeeze the shutter
button gently. Get additional
support from knees, walls, ledges…
Experiment what works for you.
More good tips here:
http://knol.google.com/k/vesna-kozelj/how-to-holdthe-camera-with-your-hands/3k0expg5xjecw/2#
Péter Tarján
5
Freezing movement
For freezing movement, you need a fast shutter speed. But how fast? It
depends on how fast the subject is moving across the frame – not the
actual speed! Distance to the subject also counts. Subjects moving
towards or away from the camera need slower shutter speed than those
moving across the frame. Also: for close subjects, you can use a flash – it
almost always freezes the movement.
Subject
Speed
Distance
efl
across
Direction
of motion
toward
diagonal
car
80 km/h
30 m
100 mm
1/1000 sec 1/250 sec
1/500 sec
train
160 km/h
50 m
35 mm
1/500 sec
1/125 sec
1/250 sec
jogger
10 km/h
5m
100 mm
1/750 sec
1/180 sec
1/300 sec
jet plane
800 km/h
2000 m
400 mm
1/500 sec
1/125 sec
1/250 sec
Péter Tarján
6
Effect of freezing movement
Péter Tarján
7
Blurred movement
Fast shutter speeds sometimes fail to Panning: tracking a subject with the
convey the dynamism of a moving camera, using slow shutter speed, causing
the subject to remain sharp and background
subject: a speeding car may look
to blur. Technique:
just like a parked one. Choosing a
• hold the camera steady with two hands
slow shutter speed blurs the
• swing your shoulders from your waist,
movement, which may work
without moving your feet
better. Shutter speed shouldn’t be
• leave more space in front of the moving
just slighly slow (blur without the subject than behind
artistic effect) or too slow (image • follow the subject across and press the
may be unrecognizable). Rule of
shutter button smoothly
thumb: 4 stops slower shutter than • take lots of shots to get a few that work
what you would use for freezing
the action.
Péter Tarján
8
Blurring
Péter Tarján
9
Extended exposures
In low light, exposures of more than 1 second
may be needed. Some tips:
• Support the camera.
• If the camera is supported, you are free to
choose any shutter speed. Choose shutter
speed/aperture to suit your needs.
• Choose the lowest ISO setting to minimize
noise.
• Use self-timer/shutter release cable/remote
control to fire the camera.
• Avoid the widest aperture settings to
maximize image quality.
• If you can’t get a slow enough shutter
speed, use a neutral density filter.
• Low-light shots tend to be overexposed by
the camera; correct for that or use manual
exposure.
Camera supports
• whatever you find
• beanbag
• unipod (monopod)
• tripod (pan-tilt head, ball-and-socket
head)
head (with camera
platform and quickhandle
release shoe)
crank
center column
Péter Tarján
telescopic legs
10
Effect of extended exposures
Péter Tarján
11
Depth of field
In principle only objects at a given
distance from the lens are sharp
– everything closer or further
away are blurred to varying
degrees. The blur is invisible
for a given range of distances
around the focusing distance,
so everything within that range
looks sharp. This range is
called the Depth of Field
(DoF). Depth of Field depends
on a number of factors.
Péter Tarján
Factors determining DoF:
• aperture: the smaller the aperture
(higher f-stops), the more the DoF.
• focusing distance (subject distance):
the farther away the focus is, the more
the DoF.
• focal length (zoom setting): the shorter
the focal length (=wide angle) the more
the DoF.
• “circle of confusion”: how big a circle
you are willing accept as “point”.
Subjective! It also depends on image
magnification and how closely it is
viewed.
12
Depth of field: aperture effect
7.4 mm focal length (35 mm efl), focus on red die
Péter Tarján
13
Depth of field: focal length effect
focus on red die, f/4.0
Péter Tarján
14
Depth of field: focusing distance effect
efl 65 mm, f/3.2
Péter Tarján
15
Depth of field: size matters
Is the yellow die sharp? It depends on the magnification and your
definition of “sharp”.
Péter Tarján
16
Maximizing depth
Use the controls together
to maximize DoF: use
wide lens/zoom
setting, close the
aperture, get further
away from the
foreground elements.
Multipoint autofocus
helps.
The through-the-lens
(TTL) viewfinder of
bridge and SLR
cameras may give an
idea of DoF.
Péter Tarján
17
Minimizing depth
Throwing things out of focus is
usually much more difficult
on digital cameras – SLRs
rule here. The main things
you can do:
• use long telephoto
• use wide aperture
• get close to subject
Why? Keeping parts of the
picture blurred can help
concentrate on the main
subject and can result in
more powerful pictures.
Péter Tarján
18
focus
DoF<1 cm!
More DoF tips
Bokeh: out-of-focus background
with smoothly blurred highlights
when taking pictures of
people or animals, always
focus on the eyes! We
tend to look at them first
and blur is the most
annoying when in the eyes
DoF in close-up photography is
extremely narrow – fight it or
use it to your advantage
Péter Tarján
19
Aperture and lens resolution
In several picture-taking situation, more than one shutter speedaperture combination yields a shake-free picture and enough
DoF. In that case, you can take one other factor into
consideration: lens resolution.
Lenses provide their best resolution at their mid-apertures. Wider
settings decrease resolvable detail because lenses work better
optically near their center than their edges. At small apertures,
diffraction on the edges of the aperture itself causes another drop
in image quality. Quality decrease due to diffraction is worse for
smaller sensors. Thus, SLRs can use narrower apertures
(typically f/22) before diffraction becomes significant than zoom
compacts (typically f/8) or bridge cameras (f/11).
Bottom line: use a mid-aperture setting whenever you can.
Péter Tarján
20
Focal length
Changing the focal length of the
lens by zooming changes the
angle of view of the camera.
This is a very important
compositional tool:
• useful for cropping when taking
the picture
• allows you to maximize sensor
effectiveness
• changing it together with the
subject distance, it gives more
flexibility in choosing
background
• allows you to take very
different types of shots.
Péter Tarján
21
Perspective
same perspective!
Perspective is the optical effect
that makes distant objects
appear smaller than close
ones and parallel lines seem
to converge. It gives vital
clues about depth in the
picture.
Perspective depends only on the
distance! But using different
focal lengths can change the
picture because telephoto
lenses are used from further
away – and that changes
perspective.
Péter Tarján
different perspective
22
Manipulating the background
Whether using wideangle or telephoto
lenses, you can end
up with very similarlooking pictures.
What can change
dramatically when
you change focal
length (and subject
distance) is what is
in the background
and how it looks
(DoF, perspective…).
Péter Tarján
23
Wide-angle lenses
Wide-angle lenses offer a
wider field of view than
our eyes. Uses:
• fit a lot of things into
the frame
• exaggerate foreground
• create a wide DoF
Problem: barrel distortion
Péter Tarján
24
Telephoto lenses
Telephoto lenses offer a
narrower field of view
than our eyes. Uses:
• bring distant objects
“closer”
• “compress” distances
between objects
• create a narrow DoF
Problem: heavy,
magnifies camera
shake
Péter Tarján
25