"Fixed focal distance or zoom lens or both?"
In the area of macro, standard and wide angle optics fixed focal distance with the best light intensity reach the highest image quality. In addition there are substantial advantages in viewfinder brightness. Only for fixed focal distance can dome glasses be precisely calculated and thus offer excellent brilliance and corner sharpness. In spite of these facts zoom lenses are becoming more and more popular due to their versatility. Because front ports can only be calculated for one focal distance, compromises have to be made in the optical implementation of zoom lenses. We therefore adapt our ports to the shortest focal distance respectively in order to achieve optimal results. As conclusion one can say that fixed focal distances belong to the standard equipment of every underwater photographer - zoom lenses can add to the system but can never replace the fixed focal distance.