The glow appears directly opposite the sun around the shadow of the head or camera.
Someone in a group will see the holy glow only around their own head.
Large drops of dew produce it.
Unlike the glory it is a geometrical optics effect rather than diffraction.
The sun's rays are focused by the dew drop which is sometimes suspended on leaf hairs away from the actual leaf surface.
The drop acts acts as a rather poor lens. Spherical lenses suffer from 'spherical aberration' in that rays passing near the centre are brought to a longer focus than those passing nearer the rim. The result is a broad patch of bright sunlight on the nearby leaf surface.
Some light from the bright spot shines back through the drop in roughly the same direction from whence it arrived. The backward going light is seen as a glow around the antisolar point - the 'heiligenshein'.
See also the 'dry heiligenschein' or opposition effect.
Background image by Taavi Babcock.