The ELECTRONIC FLASH EM-140 DG Macro is designed to work with digital SLR cameras of most popular manufacturers. The EM-140 DG is ideal for photographing subjects in fine detail when the shadowless mode is used and is extremely effective for scientific and medical applications. Dual flash tubes can fire simultaneously or separately. Using only one flash tube creates a shadow which can give a three-dimensional feeling to the subject. The flash features a guide number of14 w/ISO 100.
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Sigma,EM-140 DG Macro Flash for Nikon