Depth
of Field
A presentation for Kelso Camera Club
by Norman Dodds
What is depth of field?
• Depth of Field is the amount of a photograph
which is in acceptably sharp focus from the
foreground to the background
Why is it useful to understand depth of field?
• It allows a photographer to control the amount
of the photograph which is in sharp focus to
enhance the effectiveness of the image
Everything in focus
Main subject in focus –
background blurred but
recognisable
Main subject in focus –
background totally blurred
What influences depth of field?
• The focal length of your lens:
 wide angle lens = more depth of field
 telephoto = less depth of field
• The distance from the subject:
 further away = more depth of field
 closer = less depth of field
• The aperture of your lens
Aperture
• Aperture is the opening in your lens which lets in light
reflecting from your subject
• Aperture is measured in f stops. Typically lenses
will have apertures from f2 to f36
• Just to confuse, large apertures have small numbers
and small apertures have big numbers!
Aperture
• Each aperture allows in half or double the amount of light
as you move up or down the f stops
• Your camera may also be able to move up and down the
scale in smaller steps with 2 or 3 positions between the
‘official’ f stops
• Aperture has a significant impact on depth of field:
 A large aperture will give a small depth of field
 A small aperture will give a greater depth of field
Why does aperture affect depth of field?
• The explanation is a little bit technical:
The non-technical explanation
is simpler - it just DOES!
That works for me!
F 5.6
1/3200
small depth of field
F 11
1/1000
medium depth of field
F 36
1/80
large depth of field
How do you work out what the DoF will be?
• There are 5 possibilities:
 Ignore it – don’t worry…. be happy!
 Use the depth of field preview if your camera has one.
This provides you with a visual check
 Use the depth of field scale if your camera has one
How do you work out what the DoF will be?
• There are 5 possibilities:
 Ignore it – don’t worry…. be happy!
 Use the depth of field preview if your camera has one.
This provides you with a visual check
 Use the depth of field scale if your camera has one
 Use a depth of field calculator
Get this online
How do you work out what the DoF will be?
• There are 5 possibilities:
 Ignore it – don’t worry…. be happy!
 Use the depth of field preview if your camera has one.
This provides you with a visual check
 Use the depth of field scale if your camera has one
 Use a depth of field calculator
 Make an educated guess!
Hyperfocal Distance and Focussing
• The hyperfocal distance is the closest distance at which a lens can
be focused while keeping objects at infinity acceptably sharp.
• When the lens is focused at this distance, all objects at distances
from half of the hyperfocal distance to infinity will be acceptably
sharp.
Hyperfocal Distance and Focussing
• There are three ways to set your focus to the hyperfocal distance:
 Use the scale on your lens – if you have one!
Hyperfocal Distance and Focussing
• There are three ways to set your focus to the hyperfocal distance:
 Use the scale on your lens – if you have one!
 Use a chart
Get this online
Hyperfocal Distance and Focussing
• There are three ways to set your focus to the hyperfocal distance:
 Use the scale on your lens – if you have one!
 Use a chart
 Guess!
Using depth of field
•
•
•
•
•
•
•
Set your camera mode to AV - Aperture Value
Choose your subject and compose your shot
Set your chosen aperture
If you have a depth of field preview, use that to check the DoF
Check your shutter speed
If it’s fast enough – take the picture
If it’s too slow:
 Use a tripod ……. OR
 Increase the ISO until the shutter speed is acceptable
Shutter Speed
• Shutter speed determines the amount of time the lens
remains open when you press the button
• Similar to aperture, shutter speeds double or halve
the amount of time the lens is open as you click
through the different speeds
• A photograph’s exposure is set by a combination of shutter
speed and aperture
• Shutter speed has no impact on depth of field
Finding out more
• Google ‘depth of field’
• Dofmaster website
Questions?