Pentax SF10 - Page 32

(2) Using a manual aperture setting:
(Please read this section after you finish reading
the ^'OPERATION OF MAJOR FUNCTIONS"
section.)
When you wish to increase the depth of field, you can
manually select a desired aperture. In order to select
an aperture manually, the camera must be set in
the Aperture-Priority AE mode (see page 38) or
the Metered Manual mode (see page 40).
Flash recommendation signals
Poor lighting
Backlighting
Aperture-Priority AE
O
O
Metered Manual
X
O
To calculate the effective RTF range with the selected
aperture, the following formula can be used:
e Maximum distance: (G.N.) ^ (aperture)
• Minimum distance: (Maximum distance) ^ 5
(This formula cannot be used for a subject closer than
0.7 meters.)
• 28
If the subject distance is known beforehand, calculate
the aperture based on that distance.
• (G.N.) -i- (distance) = (aperture)
3k If the aperture calculated by this formula does not
correspond to any f-number found on the aperture
ring (for example, the aperture "3/‘ which is between
"4" and "2.8'*), set the aperture to the smaller
f-number ("2.8").
The RTF's guide number (G.N.) varies according to
the ISO speed of the film in use, as indicated in
the chart below.
ISO film speed
Guide number
ISO 25
G.N, 6
ISO 50
G.N. 8.5
ISO 100
G.N. 12
ISO 200
G.N. 17
ISO 400
r G.N. 24
To use the RTF at aperture f/4 with ISO 100 film:
1. Set the lens aperture ring to f/4.
2. Calculate an effective flash range.
12 (G.N.) -i- 4 (aperture) = 3m (maximum
distance)
3m (distance) ^ 5 = 0.6m (minimum
distance -* ■ 0.7 (actual minimum distance)