1. Depth of Field
By: Amit Chawla

2. Definition:
 The “Changing Zone of Sharp Focus”,
either side of object distance on which
you actually focused, is known as depth
of field.
 It is the distance between nearest and
furthest parts of a subject that can be
imaged with acceptably sharp details, at
one focus setting.

3. Practical Significance:
 By choosing a shallow depth of field, you
can isolate one item from others at
different distances.
 It is basically used to create emphasis
and suggest surroundings..

4. Factors of Depth of Field
1. f-number (or Aperture Number)
2. Subject distance from Lens
3. Focal Length of Lens
4. Permissible area of circle of confusion.

5. 1. APERTURE ( f. Number)
The smaller the aperture, the higher the
depth of field (the other two factors
remaining the same).
For example, if the lens focal length and
the shooting distance stay the same, the
depth of field is much deeper at f/16 than
at f/1.4.

7. Comparison
f - 2.8 f – 5.6 f-8

8. 2. Focal Length
 The shorter the lens focal length, the
higher the depth of field (the other two
factors remaining the same).
 For example, comparing a 28mm lens
with a 50mm lens at the same aperture
and shooting distance, depth of field is
deeper with the 28mm lens.

9. Changing Focal Length
Photos below were taken by 35 mm camera at constant distance from subject.
28 mm lens 50 mm lens
70 mm lens 210 mm lens

10. 3. Shooting distance
 The greater the shooting distance, the
deeper the depth of field. i.e. other two
factors remaining the same).
 For example, if the subject is photographed
from three and then from seven meters
away, the zone of sharpness in the
foreground and background is greater at
seven meters.

11. Shooting Distance

12. REMEMBER:
 Another characteristic of depth of field is that
it is generally deeper in the background than
in the foreground.
 Although, people ask for detail throughout
the picture in most commercial/record
photography, the picture with minimum D of
F will have maximum information.

13. HOW DEPTH OF FIELD WORKS
 Before understanding the working of D of F one
needs to first understand that how exactly a lens
critically focuses an image point depending upon
how far a lens is from the subject.

14. C A a'
B
B
c' C
A
Depth of Field
 B is the only point of object which is forming a Point
of Focus on the Film. Light from other parts of the
subject, nearer or farther from the lens, comes to
focus farther away or nearer to the film.
 Thus discs are formed instead of points of light.
These discs are known as Circles of Confusion.

15. Permissible Circle of Confusion
 Large discs gives image an un-sharp
appearance because our eyes have a limited
resolving power.
 A permissible Circle of Confusion is the one
which our eye can resolve as a point instead
of a disc.

16. Depth of Focus
By: Amit Chawla

17.  Depth of focus is often confused with depth of field,
but in reality the two are very different.
 Where DoF is “Changing Zone of Sharp Focus”,
either side of object distance on which you actually
focused;
 Depth of focus, is a measurement of how much
distance exists behind the lens wherein the film
plane will remain sharply in focus.
 It can be viewed as an action which is occurring on
the opposite side of the lens.