Maybe the photo studio had a contract with the Regiment?
Hand coloured photographs stunning every time
Most garrison towns had a number of photographic studios, some of which naturally favoured by certain regiments. At the same time the Army at Regimental level had photographic units that did portraits as well. By 1915 the photographic units were now at battalion level, and there were even private photographers in Saxon units that opened up their own studios for when they were in reserve.
You could in theory take a picture of your frontline, get it printed on a postcard and send it home!
By 1916 every German town had a fast photostudio which tuned you around in about 20 minutes.
The Germans and photographs are interesting, they loved them, they were the selfies of their day. Some of this was due to their leads in chemical and opitcal industries, national pride where every state job had a uniform and a pickehaube or shako.
The Germans took way more photographs than any of the other combatants which has left us with a wonderful record, it is (to me) a fascinating subject the realtionship between photgraphs and the people and the war