Both IDL and PBR require the surroundings to be modeled, either as a real geometry model or as a pattern on a sphere. The charm of IBL is that you can light the figure in an otherwise empty scene, render over transparent background and have them ready 'cut out' to be collated into the environment.

The process of making a high range IBL is quite tedious and technical. It consists of making multiple pictures with different exposure times, and filter and merge them based on the light value, taking from each shot only the areas with light values between say .25 and .75, and add them in the collage with corrected light values depending on the exposure, so the .25 to .75 part of a 4 times under-exposed shot would be mapped back to exposure 1.0 to 3.0. There were some tools that could do it for you.

Today the quick and dirty is to use a (phone) camera with an HDR option. It does a similar thing, compress the central lightness and add detail in the blacked-out and washed-out areas. Result however is just a .jpg with light values between 0 and 1.You will have to tell Poser to scale. Where not entirely correct results may do for your artistic purposes. Of course clip the image square around the sphere.