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% guide numbers vary with the ISO film speed, shutter speed, and zoom-
head position.
• For film speeds other than ISO 100, multiply the guide numbers by the
factors shown in the above chart.
For example, for a film speed of ISO 400, with the zoom-head adjusted to 35mm,
and a shutter speed of 1/500 sec., the % guide number is 12 x 2 = 24 (m), or
39 x 2 = 78 (ft).
Notes on flash photography in FP High-Speed Flash sync %
• Do not use the built-in wide flash adapter.
When used, M20 or M18, ƒ and % blink on the LCD panel as a
warning.
• Detaching the SB-28
When you remove the SB-28 from the F5, F100, F90X/N90s or F90-
Series/N90, be sure to cancel FP flash operation. If the flash is removed
with the FP setting, % blinks as a warning.
51
Shutter speed
1/250 sec.
1/500 sec.
1/1000 sec.
1/2000 sec.
1/4000 sec.
Zoom-head position
24mm 28mm 35mm 50mm 70mm 85mm
14/46 15/50 17/56 20/65 23/74 24/77
10/33 11/36 12/39 14/46 16/52 17/56
7/23 7.5/25 8.5/28 10/33 11/36 12/39
5/16 5.3/17 6/20 7/23 8/26 8.5/28
3.5/11 3.7/12 4.2/14 5/16 5.7/18 6/20
% guide numbers (at ISO 100; for meters/feet)
Factor
ISO film speed
x 0.5 x 0.71 x 1.4 x 2 x 2.8
25 50 200 400 800
Adjustment factors for other ISO film speeds