The arithmetic nobody does in advance
A single group photograph takes roughly three to five minutes once you account for locating the people, moving them into position, quietening them, and taking several frames so someone's eyes are open. That sounds manageable until you count the shots: immediate family, both sets of parents, wedding party, grandparents, old friends, colleagues. Eight groups is forty minutes, and that is before the photographer asks for one more.
The delay compounds because assembly is sequential. You cannot gather the bride's siblings while those same siblings are still in the previous shot. Each group must fully disperse before the next can begin, which means the list runs in series, not in parallel. There is no shortcut that the arithmetic allows.
What makes this genuinely hard is that the people who need to be in photographs do not know where they are supposed to stand, and the people who do know — the couple — are in every frame and cannot go and find anyone. Someone else must be assigned to call and collect. Without a named person holding a printed list, you will spend two of your three minutes per shot doing a headcount that comes up one short.
The fix is mechanical: write the shot list before the day, number it, and give a copy to whoever is running the room. Assign a second person whose only job for that block is to know where the next group is standing before the current frame is taken. Keep the list short — ten groups is a ceiling, not a target. Every shot you cut before the day is time that stays in the schedule; every shot you cut on the day is time already lost.
The run-sheet as a whole tends to lose time in exactly the places that feel brief on paper. Photographs are the clearest example: one line, forty minutes, and a compounding delay that does not announce itself until the light has changed and the caterer is waiting.
Treat group photography as a logistics block with a named coordinator, a capped list, and a buffer after it. It will still run long. It will run less long.