1. Is 90mm a wide angle lens or a telephoto lens?
2. If I’m taking a picture of a building, why would my perspective change if I switch from a wide angle lens to a telephoto lens?
3. Name one reason why I would want to take a portrait up-close with a wide angle, and one reason why I would want to take a portrait far away with a telephoto.
Week 8 Quiz
LensesLenses define 2 important things:• Angle of view (focal length)• Aperture
Film/SensorWhere the light is recorded
LensBends the light
Trajectory of lightSubject
Source of light
FocusingA look at the overall camera system
Light converges at sensor
Light converges past sensor
Light converges before sensor
Result:
‘In focus’
‘Out of focus’
‘Out of focus’
Result:
‘In focus’
Circle of confusionImage doesn’t have to
perfectly converge. If it converges within a “circle of
confusion”, it is still ‘in focus’
‘In focus’
‘Out of focus’
In focus
Out of focusOut of focus
•Things at a certain distance are “in focus” (perfectly sharp)•The further from this distance, the blurrier things are•There is a range of distance where things are ‘sharp enough’ to be considered ‘in focus’. This range is known as the “depth of field”
Amount of Blur
Depth of field
Depth of fieldRange that is ‘in focus’
Focus point
Near limit of focusFar limit of focus
Film/SensorWhere the light is recorded
Circle of confusionMaximum non-convergance
allowed to be ‘in focus’
Depth of field
Circle of confusion
When using a bigger lens (larger aperture), the depth of field shrinks
Depth of field
Circle of confusion
Longer subject distances mean larger depth of field range
Circle of confusion
Longer focal lengths mean smaller depth of field range
Depth of field
A = aperture f-number (e.g. f5.6)f = focal length (e.g. 50mm)d = distance to subject (e.g. 3000mm)c = circle of confusion (e.g. .02mm)
Factors to note:Smaller apertures (larger f-number) gives larger depth of fieldShorter focal length gives larger depth of fieldLonger distance to subject gives larger depth of fieldLarger circle of confusion gives larger depth of field
(Acd)-f2Ac(fd) =fieldof Depth 24
2
0 2 4 6 8 10 120
2000
4000
6000
8000
10000
12000
14000
dof
Aperture
Dept
h of
Fie
ld (m
m)
As aperture increases, depth of field increases
0 50 100 150 200 250 300 3500
1000
2000
3000
4000
5000
6000
7000
dof
Focal length (mm)
Dept
h of
Fie
ld (m
m)
As focal length increases, depth of field decreases.At very wide focal lengths (ultrawide), depth of field increases rapidly
Translating focal length into angle of viewAngle of view Focal length - 35mm Focal length - 1.5x APS-C Focal length – 1/1.7”
62.01° 36mm 24mm 8mm
Actual focal length35mm equivalent focal length
0 5000 10000 15000 20000 25000 300000
50000
100000
150000
200000
250000
dof
Subject distance
Dept
h of
Fie
ld
As subject distance increases, depth of field increasesAt very long subject distances, depth of field increases rapidly (hyperfocal distance)
0 50 100 150 200 250 3000
500
1000
1500
2000
2500
dof
Focal Length
Dept
h of
fiel
d
For a constant magnification, depth of field is roughly the same across all distance/focal length combinations
Uses of large depth of field
Landscape/scenery
Architecture Small depth of fieldMacro
Uses of small depth of field
Portraits
Flowers
Sports
Isolation
Bokeh: quality of out-of-focus “blur”
Focal length rangesTwo types of lenses: Zooms (variable focal length) and Primes (fixed focal length)
Different focal lengths are useful for different things
Large aperture zooms• As large as f/2.8 aperture• Expensive! Canon 17-55 f2.8
$999
Canon 70-200 f2.8$1139
Focal length rangesTwo types of lenses: Zooms (variable focal length) and Primes (fixed focal length)
Different focal lengths are useful for different things
Large aperture primes• Very large apertures (f2, f1.8, f1.4, f1.2)• (Mostly) Cheaper than large aperture zooms• Fixed focal length (angle of view)
Nikon 85mm f1.8$419
Canon 50mm f1.4$316
Canon 50mm f1.8$83
Portrait AssignmentFocus on the following elements:• Lighting (direction, intensity)• Vantage point (camera direction, setting, background)• Perspective (subject distance vs. focal length)• Depth of field• Directing the subject (poses, props, expression)
Before shooting: Login to the gallery, choose 3 photos and evaluate each of these elementsWhat was done, how it worked out, and how you would do it
• Lighting (direction, intensity)• Vantage point (camera direction, setting, background)• Perspective (subject distance vs. focal length)• Depth of field• Directing the subject (poses, props, expression)
• Lighting (direction, intensity)• Vantage point (camera direction, setting, background)• Perspective (subject distance vs. focal length)• Depth of field• Directing the subject (poses, props, expression)
• Lighting (direction, intensity)• Vantage point (camera direction, setting, background)• Perspective (subject distance vs. focal length)• Depth of field• Directing the subject (poses, props, expression)
• Lighting (direction, intensity)• Vantage point (camera direction, setting, background)• Perspective (subject distance vs. focal length)• Depth of field• Directing the subject (poses, props, expression)
• Lighting (direction, intensity)• Vantage point (camera direction, setting, background)• Perspective (subject distance vs. focal length)• Depth of field• Directing the subject (poses, props, expression)
• Lighting (direction, intensity)• Vantage point (camera direction, setting, background)• Perspective (subject distance vs. focal length)• Depth of field• Directing the subject (poses, props, expression)
• Lighting (direction, intensity)• Vantage point (camera direction, setting, background)• Perspective (subject distance vs. focal length)• Depth of field• Directing the subject (poses, props, expression)
• Lighting (direction, intensity)• Vantage point (camera direction, setting, background)• Perspective (subject distance vs. focal length)• Depth of field• Directing the subject (poses, props, expression)
• Lighting (direction, intensity)• Vantage point (camera direction, setting, background)• Perspective (subject distance vs. focal length)• Depth of field• Directing the subject (poses, props, expression)
• Lighting (direction, intensity)• Vantage point (camera direction, setting, background)• Perspective (subject distance vs. focal length)• Depth of field• Directing the subject (poses, props, expression)
• Lighting (direction, intensity)• Vantage point (camera direction, setting, background)• Perspective (subject distance vs. focal length)• Depth of field• Directing the subject (poses, props, expression)
• Lighting (direction, intensity)• Vantage point (camera direction, setting, background)• Perspective (subject distance vs. focal length)• Depth of field• Directing the subject (poses, props, expression)
• Lighting (direction, intensity)• Vantage point (camera direction, setting, background)• Perspective (subject distance vs. focal length)• Depth of field• Directing the subject (poses, props, expression)
• Lighting (direction, intensity)• Vantage point (camera direction, setting, background)• Perspective (subject distance vs. focal length)• Depth of field• Directing the subject (poses, props, expression)
• Lighting (direction, intensity)• Vantage point (camera direction, setting, background)• Perspective (subject distance vs. focal length)• Depth of field• Directing the subject (poses, props, expression)
• Lighting (direction, intensity)• Vantage point (camera direction, setting, background)• Perspective (subject distance vs. focal length)• Depth of field• Directing the subject (poses, props, expression)
Portrait AssignmentFocus on the following elements:• Lighting (direction, intensity)• Vantage point (camera direction, setting, background)• Perspective (subject distance vs. focal length)• Depth of field• Directing the subject (poses, props, expression)
Before shooting: Login to the gallery, choose 3 photos and evaluate each of these elementsWhat was done, how it worked out, and how you would do it
Partner up with someone in the class (right now, or post on the forums)
Come up with your own themeYou’ll have to present your photoshoot and talk about each of the elements
If you want, shoot in RAW (we’ll be talking about processing after Spring Break)