Hi Mark, which ones are the polar hdri files? I've always used what HDRShop calls "Longitude/Latitude" or panorama type, available at the lightworks-user.com site (looks like a regular photo). I convert any other hdri files in HDRShop using: Image->Panorama->Panoramic Transformations The manual says Carrara hdr files should "completely fill the rectangle of the image" which is what I've always gone by. Thanks