Perspective/Orthographic views

In the perspective view (the default), objects which are far away are smaller than those nearby. In the orthographic view, all objects appear at the same scale. Since some prefer one over the other, both options are available. Perspective viewpoints give more information about depth and are often easier to view because you use perspective views in real life. Orthographic viewpoints make it much easier to compare two parts of the molecule, as there is no question about how the viewpoint may affect the perception of distance.