HDR is what some folks are referring to when the DR (dynamic range) setting is changed from 100 to 200 or higher, the shadows are boosted and the highlights are lowered. As long as you stay at DR 100, the files will be regular sized and un-affected. The DR setting is what I believe itchy is asking about.
p.s. Shooting in IR comes up every now and then, maybe your and @Ninon’s collaboration can pull together some info into one place (hope, hope).