ExpoImaging ExpoAperture2 Manual (Imperial/Standard) - Manual (Page 15)

ExpoAperture 2 Depth-of-Field Guide Manual
V 1.0
15
2.E - Determining The Correct Aperture and Focal Point
Use the following method to determine the correct aperture and focus settings for a specific
depth-of-field. Your camera should be in Aperture Priority mode and, unless your subject is
at the computed focal point, your camera should be in manual focus mode so that you can
manually focus at the correct distance.
EXAMPLE:
The photographer is using a 35mm film camera with a 50mm lens and wants a depth of field
of 6’ to 30’. What aperture should the photographer use to achieve this depth-of-field?
STEP 1 –
On the Guide’s Distance Dial find the distance range that
you would like to be in focus, in this example, 6’ to 30’.
STEP 2 –
Count the number of Focus Zones contained within the
range of distances you have selected. Each alternating grey
and white arc represents one zone. Here, the range of
distances covers 4 zones.
STEP 3 –
Note the distance at the center point of the Focus Zones
you have selected. In this case, you will find 10 feet at the center of the 4 zones you found
in Step 2. This point is called the point of critical focus, and it will be the focal distance to
which you will want to set your lens to achieve the desired depth-of-field.
STEP 4 –
Turn the guide over and set the Focal Length Dial to
the correct format or desired circle-of-confusion that
you wish to use -- here, 35mm film or 30 microns --
by turning the dial until the correct value appears in
the cutout on the Focus Zone Dial.
STEP 5 –
Rotate the Focus Zone Dial of the guide to expose
the focal length of the lens you are using through the
small window labeled “FL – mm,” here, 50 mm.
STEP 6 –
Find the aperture (f/stop) above the number of Focus Zones you determined in Step 2 (4
zones). f/18 is the aperture located directly above 4 zones, therefore, in order to achieve a
depth-of-field of 6’ to 30’ in this example, the photographer would set his 35mm camera to
f/18 when shooting at a 50 mm focal length.