Excellent photos! Sometimes I just can’t get over how shiny their hauben were! Couple that with new mercury gilt fittings and obviously, these helmets were very impressive.
Yes agree…I am guessing in that shine you can see the reflection of the window the studio used to light the portrait. if only these were color images back then.
Shoulder shot appears to be a OYV with Feld-Artillerie-Regt. General-Feldmarschall Graf Waldersee (Schleswigsches) Nr.9
(Itzehoe) VIII Armee Korps. Helmet is clearly a private purchase.