Inside the booth
Keep a staggered group sharp in a narrow portrait space
Arrange faces closer to one depth before increasing camera settings.
When two people stand at different distances from the camera, one face can fall outside the sharp area. First solve the arrangement; a very small booth may not have enough depth for a large staggered pose.
Mark the focus point
Ask everyone to stand still and choose the face nearest the centre of the intended frame. Focus there and take a test. Inspect eyes at full size if possible; a tiny thumbnail can hide missed focus.
Reduce the depth gap
Bring faces onto a shallow arc around the camera rather than placing one far behind another. Keep shoulders close and turn bodies slightly so people fit side by side without leaning forward. If space is tight, use a single row instead of a dramatic stagger.
Retest the edges
Take a second frame and inspect the nearest and farthest eyes. If one remains soft, increase depth of field with a smaller aperture when the camera allows, add light if shutter speed becomes too slow, or simplify the pose. Do not rely on sharpening to recover missed focus.