Upward angles and DOF

Shooting upward to a vertical structure with a telephoto lens means that deph of field is limited.  This happens because the plane of the digital sensor is oblique to the plane of the subject when the camera is angled up.  In a picture like this, you wouldn't want only part of the architecture and the costumed models to be in focus.  Complete depth of field here is crucial to the success of the image.  Therefore, I used f/11 and chose aperture priority for the shot.  The focal length was 105mm and I used 640 ISO.  This unique 15th century spiral staircase has just recently opened after several years of construction.