f = 50 mm (standard photographic objective)
f = 100 mm (telelens)
f = 300 mm (telelens)
f = 1200 mm (telescope, primary focus)
f = 3500 mm (telescope, oculair projection)
f = 6000 mm (telescope, oculair projection)
The next images show a few examples of the same object, photographed with different focal lengths from 50 mm - 6000 mm.
f = 50 mm (standard photographic objective)
f = 100 mm (telelens)
f = 300 mm (telelens)
f = 1200 mm (telescope, primary focus)
f = 3500 mm (telescope, oculair projection)
f = 6000 mm (telescope, oculair projection)
You can see the enormous difference between f = 50 mm and f = 6000 mm.