Nikon Autofocus Speedlight SB-22 Instruction Manual page 21

^ Confirm whether the green in-focus
' indicator LED iights up, then fuliy depress
the shutter reiease button.
If focus-not-possible indicator LED (x) remains lit
when using the Nikon F-501/N2020, or if focus indi­
cator LED (•) blinks with Nikon F-401/N4004, auto­
focus flash photography is impossible. Focus manually
on the clear matte field.
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