Exposure

1
Exposure

• Aperture

2
(No Transcript)
3
Aperture is Like an Iris in an Eye

• Aperture regulates the amount of light exposed to
  the film at a given time

4
Aperture

• Measured by f-stops
• f-stops are fractions
• f2 on a 50mm lens means maximum aperture opening
  is ½ focal length or 25mm
• Increase the aperture 1-stop doubles the light

5

• Typical f-stop numbers
• 2.8, 4, 5.6, 8, 11, 16, 22
• At a 50mm lens
• f2.8 is 50/2.8 17.7mm
• f4.0 is 50/4.0 12.5mm ? 1/2 light from 2.8
• f5.6 is 50/5.6 8.9mm ? 1/4 light from 2.8
• f8.0 is 50/8.0 6.3mm ? 1/8 light from 2.8
• f11.0 is 50/11 4.5mm ? 1/16 light from 2.8
• f16.0 is 50/16 3.1mm ? 1/32 light from 2.8
• f22.0 is 50/22 2.3mm ?1/64 light from 2.8

6
Aperture

• Because of the Fraction There is an Inverse
  relationship
• Smaller number larger opening
• Larger number smaller opening

7
Aperture

• This aperture is f/16 (sometimes written f16 or
  f-16)
• This aperture is f/2.8

8
Aperture

• Going from left to right is stopping down the
  aperture.
• The lens has been stopped down five stops
• f/2.8 (1) f/4 (2) f/5.6 (3) f/8 (4) f/11 (5)
  f/16
• The f-stop will increase in number
• Confusing?

9
Aperture

• If you are shooting around the school you will be
  forced to open up (low number)
• It is just too dark

10

• Depth of field (DOF) is the distance in front of
  and behind the subject which appears to be in
  focus.

11

• Decreasing the DOF can decrease a cluttered
  background
• These two students would not stand out as much if
  the background was more in focused

12

• Aperture value (also zoom) will influence the
  depth of field

13
f22 and Shutter Speed 1.6 s
14
f20 and Shutter Speed 1.3 s
15
f18 and Shutter Speed 1.0 s
16
f16 and Shutter Speed 0.5 s
17
f13 and Shutter Speed 0.3 s
18
f9 and Shutter Speed 1/4 s
19
f6.3 and Shutter Speed 1/8 s
20
f3.2 and Shutter Speed 1/30 s
21
f2.2 and Shutter Speed 1/60 s
22
f1.8 and Shutter Speed 1/125 s
23
Other Influence on DOF
24

• Focal length
• The greater the focal length the less of the DOF

25
(No Transcript)
26
(No Transcript)
27
(No Transcript)
28
(No Transcript)
29
(No Transcript)
30
(No Transcript)
31
(No Transcript)
32
(No Transcript)
33
(No Transcript)
34
(No Transcript)
35
(No Transcript)
36
(No Transcript)