Before revision:  Standard methodologies that rely solely on the extraction  of facial features often fall short of accurate emotion prediction in cases where the aforementioned source of affective information is inaccessible due to head/body orientation, low resolution and poor illumination.
After revision:  Poor illumination conditions, head/body orientation and low image resolution constitute factors that can potentially hinder performance in case of methodologies that solely rely on the extraction of facial features often fall short of accurate emotion prediction in cases where the aforementioned source of affective information is inaccessible due to head/body orientation, low resolution and poor illumination.