Class Lecture on Depth of Field (Basic Photography), Aperture

1. VALUE OF OPENING
Depth of Field (DOF)
MC310: Basic Photography Class
Mass Communication Program
Ateneo de Davao University

2. DOF Defined
§ The distance in front of and beyond the
subject that appears to be in focus.

3. DOF Control: f number
§ the f-number (sometimes
called focal ratio, f-ratio)
of an optical system
expresses the diameter of
the entrance pupil in terms
of the effective focal
length of the lens.
§ Quantitative measure of
lens speed.

4. Narrow DOF

5. Circle of Confusion

6. Circle of Confusion

7. § The points in
focus (2)
project points
onto the image
plane (5), but
points at
different
distances (1
and 3) project
blurred
images, or
circles of
confusion.

8. § Decreasing the
aperture size
(4) reduces the
size of the blur
circles for
points not in
the focused
plane, so that
the blurring is
imperceptible,
and all points
are within the
DOF.

9. Sample: 35mm lens
§ A 35 mm lens set to f/11.
The depth-of-field scale
(top) indicates that a
subject which is anywhere
between 1 and 2 meters in
front of the camera will be
rendered acceptably sharp.
§ If the aperture were set to
f/22 instead, everything
from 0.7 meters to infinity
would appear to be in
focus.

10. Various Aperture Value
f/22
f/8
f/4
f/2.8

11. F 3.2

12. F 3.6

13. F 4.0

14. F 4.5

15. F5.0

17. F 5.6
F 6.4
F 7.1
F 8.0
F 9.0

18. Compare f3.2 and f9.0

19. Effect of DOF
§ At f/32, the
background is
distracting.
§ At f/5.6, the flowers
are isolated from the
background.

20. At f/2.8, the cat is isolated from the background.

21. Hyperfocal Distance