Nikon SB-28 - Manual (Page 65)

To eliminate harsh, directional shadows produced by a single flash
unit or to add additional illumination to the background, you can
attach additional Nikon Speedlights in series.
Flash shooting with more than one unit Flash shooting with one flash unit
For multiple flash operation with the SB-28, both TTL Auto Flash
t and
Manual Flash
ƒ modes are possible.
• Multiple flash operation in TTL Auto Flash
t mode is possible with cameras in
Groups I through VI and F3-Series cameras. Multiple flash operation in Manual
Flash
ƒ mode is possible with cameras in all groups.
• For applicable flash units and accessories, see pages 68-69, System chart for TTL
multiple flash.
• In multiple flash operation, first decide which will be the main unit and which the
secondary unit(s). To eliminate shadows, adjust the lighting ratio so that
illumination from the main unit is greater than that from the secondary unit(s).
Notes on multiple flash operation
• In multiple flash operation, if the electric current in the synchro circuit exceeds a
certain level, you may not be able to take a second shot after the first. In this case,
turn each of the flash units off once or disconnect the SB-28 unit from the camera.
This resets the circuits so you can resume shooting.
• In multiple flash operation, take care that the combined total of the coefficients
(numbers shown in parentheses below) for all flash units used at the same time
does not exceed 20 at 20°C (68°F), or 13 at 40°C (104°F).
Speedlight coefficients
SB-50DX (1) SB-29 (1) SB-28/28DX (1) SB-27 (1)
SB-26 (1) SB-25 (1) SB-24 (1) SB-23 (4)
SB-22s (1) SB-22 (6) SB-21 (4) SB-20 (9)
SB-17 (4) SB-16 (4) SB-15 (4) SB-14 (1)
SB-11 (1) SB-140 (1)
Coefficient numbers in parentheses are in units of 70µA.
65
Multiple flash operation in t t and ƒ flash modes