Even without the full HDR range in a Vue HDR output from a single render, I reckon it should still work slightly better than jpeg...

...for Indirect Lighting ray calculations too.

But I'm doing some experiments in Photoshop to see how effectively I can simulate a fuller range HDR, by creating three copies of the single Vue HDR render, tone-map it etc and push the exposures in opposite directions, before then recombining those three exposures into a single HDR image file, all just within Photoshop.

Really, as I understand it, the aim is just to get as wide a range as possible for the sake of the IDL pass.

In terms of the spherical panorama, as used within the Poser envsphere, functioning also as a background, then I think the HDR matters much less... in my opinion.

Even for IDL, I'm guessing having the IDL render options parameters right probably matters much more than having a true HDR.