ExpoImaging ExpoAperture2 Manual (Imperial/Standard) User Manual

Page 15

ExpoAperture

Depth-of-Field Guide Manual

V 1.0

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.