Greg Zaal writes:
I've just released a new HDRI with my highest dynamic range yet :D A crazy 27 EVs
Such a huge dynamic range (i.e. variation of brightness) was required to capture both the super-bright sunlight (without clipping the sun), and the dark shadows of the dense forest.
For comparison, most HDRIs you find are shot with only 12 EVs, which means any bright light sources like the sun will be clipped, so it will produce flat and unrealistic lighting. I make it a point with all my HDRIs to capture as much dynamic range as necessesary (usually 21 or 24 EVs if the sun is visibile) so that the lighting is as accurate as possible.
If you want to know more about what this funny "EV" number means, I ranted some more about it over here.