Rule of Thumb Focusing
At what distance you focus the camera is important
for keeping the entire garden in acceptably sharp focus.
Perhaps you have heard the following rule of thumb:
“Focus one-third into the scene.” I find this confusing.
In easier to understand terms, it simply means to focus
twice as far as the nearest foreground. That is, if the
closest part of the scene is at eight feet, focus the
camera at approximately 16 feet. Then hold this focus
distance and re-compose the scene.
For the accompanying photo, I selected 18-mm focal
length. To limit motion blur, I used a shutter speed of
1/200 sec. For good depth of field, I recommend f-stops
near f/8 to f/16. And I allowed the ISO value to adjust
itself.
Hyperfocal Focusing
Focusing at the hyperfocal distance is one that gives
the closest sharp focus while maintaining the sharpness
from there to infinity. And it further turns out that this
closest sharp focus is at half the hyperfocal distance. In
other words, the hyperfocal distance (x) is the closest
distance at which a lens can focus to keep x/2 to infinity
(∞) in sharp focus.
Focusing at Hyperfocal Distance
Focal
Length
mm
Aperature
Hyperfocal
Distance
(x)
ft.
Closest
Focus
(x/2)
ft.
18 f/8 7.13 3.57
18 f/16 3.59 1.79
24 f/8 12.64 6.32
24 f/16 6.36 3.18
Hyperfocal apps can be downloaded to your smart
phone to provide the hyperfocal distances for different
parameters and for your specific camera. I used such an
app to create the previous table for my Nikon D5200.
For example, when using an 18-mm focal length and an
f/8 aperture, the hyperfocal distance is x = 7.13 feet. The
closest distance in sharp focus is x/2 = 3.57 feet. This
sharp focus extends to infinity (∞). The below photo is an
example of hyperfocal focusing.
Hyperfocal Focusing: Draycott Gardens, 2018 Siberian and Species Convention; Focal length 18 mm, f/16, 1/160 sec, ISO 320
Winter 2019 AIS Bulletin 17