Samsung gx-1 User Manual (en)

Using an External Flash (Optional)
ƃ The red-eye reduction feature works even when only an external flash is used. (p.52)
ƃ If red-eye reduction is used when the SEF-36PZF is set as the slave unit or with the wireless
function, the preflash for red-eye reduction will trigger the external flash. Do not use red-eye
reduction when using a slave unit.
ƃ See the SEF-36PZF operating manual for details.
ƈ As with the built-in flash, red-eye reduction is available with an external flash. 
Red-Eye Reduction