When an image “opens up,” it means that objects farther away get smaller and you are in perspective view, just like the real world. Start in Perspective view, click on the viewport label, and select ‘Viewport Properties.’ The dialog that pops up has a field called ‘35 camera lens, Lens length = ? mm.’ Try 30 mm for a nice / slightly wide angle view. The lens length is accessed via the viewport label. The shorter the lens, the more you increase your field of view (like a wide angle lens or fish-eye lens)
You mean ‘Lens Length’ – not ‘camera length.’ The longer the lens, the more you lose perspective (like a telephoto lens) and ‘flatten’ out the view. The modeler (in Blender) told me it was achieved by setting the camera length. In the attached image below, notice that the drawing seems to open from the center to the corners.
