I'm sure you saw the one before that through a scope watching a large carrier TF, you could tell how real that was. Course, that could've been a US force, but let's assume it is a JP TF. Then you get the filming of the Kongo looking BB and the Fuso, obvious the film is real, hard to determine if the scope look was somewhat added, but I don't think so.
Never heard of a US sub doing rolling film of a JP TF, then the BB's, that was fairly close even with high magnification. What skipper would have a camera set up at a time like that.....
Sure most here have seen this site, but has most WW2 real film footage unedited
http://www.realmilitaryflix.com/public/department55.cfm