Lenses
camera obscura /
pinhole camera
3
Focal length is the
distance between
the lens and the
point where the light
rays converge. It
controls
magnification and
angle of view in a
picture.
5
Focal length controls
magnification and angle of view.
http://library.thinkquest.org/11355/html/typeslenses.htm
Normal (standard-focallength)
It approximates human vision.
•
• It is fast, small, light-weight, less
expensive than other lenses.
• With 35mm film or a full-frame image
sensor, a 50mm lens is considered
normal.
• The size of the film or image sensor
determines what is considered a normal
lens. The diagonal measurement of the
film or image sensor equals the normal
focal length. (For info on full frame sensor
vs. smaller sensors: http://digital-
Long
• A long lens will magnify far away
subjects.
• It is heavier, bulkier, more expensive.
Focusing is more critical.
• It can create pincushion distortion.
Short (wide-angle)
• A short focal length (less than 50mm)
increases the angle of view.
• It creates deeper depth-of-field.
• It can cause barrel distortion.
http://www.dpreview.com/learn/?/key=barrel+distortion
24mm
50mm
35mm
100mm
http://www.paragon-press.com/lens/lenchart.htm
Focal Length and D-O-F
http://images.google.com/imgres?imgurl=http://media.the-digital-picture.com/Images/Other/Focal-Length-Background-Blur.jpg&imgrefurl=http://www.the-digitalpicture.com/Reviews/Canon-EF-180mm-f-3.5-L-USM-Macro-LensReview.aspx&usg=__CCYC_gK26QTtLWjiV532L8yirj0=&h=320&w=598&sz=50&hl=en&start=4&um=1&tbnid=R6hRQaj1lIYrmM:&tbnh=72&tbnw=135&prev=/images%3Fq%3Dfo
al%2Blength%26hl%3Den%26client%3Dsafari%26rls%3Den-us%26sa%3DX%26um%3D1
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• Your distance from the subject also
affects depth-of-field. The farther away
you are from your subject, the deeper
the d-o-f.
• Your distance from the subject also
affects perspective (size relationships
between objects). The closer you get to
your subject the larger the foreground
object will appear compared to the
background objects.
12
Prime vs. Zoom
• Prime lenses contain one focal length.
• A zoom lens has many focal lengths
combined into one lens (e.g., 20mm80mm, 24mm-120mm, 80mm-200mm).
Remember when looking at a lens’
zoom capabilities only consider the
optical zoom, not the digital zoom which
will just crop the image.
Other Lenses
• Macro (or close-up
filters): for focusing
extremely close to
an object.
• Fisheye: widest of
wide angle lenses
(180 degree view)
Review of Metering
Considerations
• Substitution readings (grey card,
exposure compensation, palm of your
hand, spot meter)
• Backlit scenes (use light meter reading
for silhouette; meter up close or use
another substitution reading to get
detail in your subject)
• Low light, high contrast
• Bracket
• HDR
Histogram: displays the
distribution of tones in an image
from black to white
•
This histogram shows an almost perfect distribution of tones covering about a 4
stop dynamic range — from deep shadows on the left to just short of bright
highlights on the right. This fits comfortably within the approximately 5 stop
dynamic range capability of most digital imaging chips.
•
http://www.luminous-landscape.com/tutorials/understanding-series/understandinghistograms.shtml
Clipped Histograms
Underexposed
•
Overexposed
http://www.luminous-landscape.com/tutorials/understanding-series/understanding-