Trying to understand flash high speed sync

Started 4 weeks ago | Discussions thread
ForumParentFirstPrevious
Flat view
acs901 New Member • Posts: 6
Trying to understand flash high speed sync

I'm trying to understand Canon flash high speed sync. I have a Canon 430EXIIIRT on the hotshoe of a Canon 6D. The flash is set to ETTL and high speed sync is on.

If I shoot at...
f8.0 @ 40th
f8.0 @ 80th
f8.0 @ 160th
The exposures look broadly the same, as I would expect, the flash changes as appropriate. However if I shoot at
f8.0 @ 320th I get 1 stop underexposure. This is not what I'd expect. What am I not understanding?

 acs901's gear list:acs901's gear list
Canon EOS 6D
Canon EOS 6D
If you believe there are incorrect tags, please send us this post using our feedback form.
ForumParentFirstPrevious
Flat view
Post (hide subjects) Posted by
ForumParentFirstPrevious
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow