There's a couple of local venues with these LED's and I'm struggling to minimise the effect
here's an article on the subject http://provideocoalition.com/index.php/aadams/story/pulse_width_modulation_is_not_your_friend/
anybody have any ideas, apart from praying the GH3 has global shutter?
I looked around and this is most recommended thing (they have trial, so easy to check):
http://www.thefoundry.co.uk/products/furnacecore/features/#deflicker2
This is GH2 example
You can try to use CCD based video cameras.
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