The 4K transfer is a "mixed bag" according to expert reviews from sites like DVD Movie Guide HDR Vibrancy:
5/5 Repulsor Blasts.
: Most of the interior scenes were filmed in the massive airplane hangar where Howard Hughes built the "Spruce Goose". Iron Man 2008 4k
The Blu-ray used Rec.709 color space. The 4K disc uses DCI-P3. The 4K transfer is a "mixed bag" according