Nice test.. Poser can't handle other formats as only Light Probe /Angular map I tested it already in Poser6 with the LDRI IBL.. before..
angular maps -  lat/long are most the same family.. the lat/long is a sphere map . sphere is used to light the poser scene.. so they have something together ..
remember you can't use any background prop it will stop the light.. make tests with shadow catcher only..
I tested all the HDR IBL light sets from poser7, a little bit drama but fine..somebody heard the bell but don't know  where it come from.. I think time for a new light sets!! lol

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