Depth
of Field
The depth of field defines the
object distance over which the image is in focus.
Features
of Depth of Field
- Smaller apertures (higher F
numbers) give greater depth of field.
- Shorter focal lengths (smaller
mm numbers) give greater depth of field.
- Greater subject distances give
greater depth of field, unless a telephoto is being
used.
Effects of Aperture and Focal Length on Depth of Field
- The lens aperture does more
than control the amount of light—it also
controls the depth of field.
- The more the lens is adjusted
to a higher F number ("stopped down"),
the greater the depth of field. The more the lens
is adjusted to a lower F number (which is not called "stopped
up"), the lower the depth of field.
- Changes in focal length also
affect the depth of field.
- As focal length decreases (moves
toward the wide angle direction), depth of field
increases.
- As focal length increases (moves
toward the telephoto direction), depth of field
decreases.
- Since a wide-angle lens has
a greater depth of field, it can give both a sharp
foreground and a sharp background.
- At the same distance a telephoto
lens will have less foreground and background in
focus.
Next - Calculating
the Required Lens
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