How much light does CNTL flash "spill" into scene?

William, 1  more quick test for you to satisfy this HSS question. Take your flash and trigger flash into a room with a mirror and shoot a self portrait with and without HSS enabled.

This is what it looks like.. (and by it I didn't mean me)

Without HSS

Wireless without HSS

With HSS enabled

HSS Enabled, Note the main flash is in the exposure and the pop up isn't. The triggering pulse begins and ends entirely before the exposure.

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http://www.daisyseyecancerfund.org/Files/Awareness/photographing_rb_poster.pdf