Is a father's obedience obligatory in accompanying sisters to photograph weddings, which may lead to staying up late and fatigue, affecting the performance of Fajr prayer and hindering devotion, knowing that the father does not regularly perform Fajr prayer and will be angry if not obeyed? And is it permissible to assist in this work which involves a degree of doubt?

Obedience to the father is not obligatory if the celebration includes forbidden acts, or if attending it leads to harm, missing prayers, or assisting in something unlawful. One should try to pacify him to avoid his displeasure. As for matters that are doubtful, most scholars are of the opinion that obedience to parents is obligatory, because avoiding doubtful matters is recommended, while obeying them is an obligation, and the رضا (pleasure/contentment) of parents is a certainty.