The document discusses depth of field (DOF) in photography. It defines DOF as the distance in front of and beyond the subject that appears in focus. The document states that f-number, which is a measure of aperture diameter relative to focal length, controls DOF - higher f-numbers correspond to larger apertures and greater depth of field, bringing more of the image into acceptable focus. It provides examples of how different f-numbers change the area of the image that appears sharp, and notes that adjusting the f-number is a way to manipulate focus and isolate subjects from backgrounds.

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