Nikon Guide number at flash-to-subject distance of 1m approx .3ft, With SB-21A

GUIDE NUMBER ---------------

See the table below for guide numbers.

Guide number at flash-to-subject distance of 1m (approx. 3.3ft.)

Amount of light output				ISO film speed
in M mode	25	50	100	200	400	800
For both flash modules	6.5	9	13	18	26	36
with controller batteries	(21)	(30)	(43)	(60)	(85)	(120)
Full
For only one flash	7.5	11	15	21	30	42
module or with external
	(25)	(35)	(49)	(69)	(98)	(139)
power source·
1/4	3.2	4.6	6.5	9	13	18
	(10)	(15)	(21)	(30)	(43)	(60)
1/16	1.6	2.3	3.2	4.6	6.5	9
	(53)	(7 .5)	(10)	(15)	(21)	(30)

Unit: m(ft.)

1000 1600

41 52

(135)(171)

48 60

(156)(197)

21 26

(68)(85)

10 13

(34)(43)

•For external power source with only one flash module, see the figure indicated in the column to the right (column for one step higher film speed)

In TTL auto flash operation, for usable apertures with a reproduction ratio lower than 1: 10, use the following equation:

	guide number at	guide number at
Usable	full output	1/16 output
lis tops -	flash-to-subject	flash-to-subject
	distance	distance

In manual flash operation, for usable aperture with a reproduction ratio lower than 1:10, use the following equation:

guide number

Usable flstop = -- = ---------

flash-to-subject distance

READY-LIGHT INDICATIONS -----------

When the controller AS-12 or AS-14 is turned on, the controller ready-light comes on to indicate flash is ready to fire.

To activate the viewfinder ready-light function when us- ing the Nikon F4-series, F-801 /N8008, FA, FE2, F-501/N2020, F-301/N2000, FG or FG-20, turn on the

camera meter by lightly pressing the shutter release button.

With alkaline-manganese or zinc-carbon batteries, if the ready-light takes more than 30 sec. to light up, replace batteries with a fresh set.

Ready-Light Warning Functions

To prevent errors listed below, the ready-lights inside the camera's viewfinder and on the controller blink, after the S8-21 is turned on.

With SB-21A

Blinking ready-light

Inside

viewfinder On AS·12

00

0-

Problem and remedy

1)The AS-12'smounting foot is not securely locked. Firmly tighten lock ring .

2)The AS-12 is set at TTL with a camera other than a Nikon F3-series camera. Reset flash mode selector to M.

3)In TTL mode, the film speed setting on the camera is beyond the usable range . Use film within range of ISO 25 to 400 .

4)The flash fired at full light output in TTL mode ; lighting might be insufficient. (See page 37).

The shutter speed set on the FM2 or FE is faster than the flash sync speed. Reset to flash sync speed or slower.

40