For all other it must be purchased separately Bedauerlichweise. Nevertheless, it is the same in many respects, very useful. First may be mentioned that it laterally occurring stray light is eliminated to a certain angle. If you want to understand this effect once properly, put your camera on the table again and photograph a subject, for example. The couch, the vase on the windowsill, then leave the camera in the same position, then put them in a a distance of about 40 cm a light on and point it at a right angle to the front lens of the objective. Now they take pictures again. You now see the result. They prevent the lens hood.
Filters, these are the things that are always happy to recommend to protect the lens. Except for very special cases, these are not intended to protect the lens. Not so with the lens hood, it is a very good protection in a case although it takes usually a total loss, but the lens can be saved by the damping.
The lens hood for the lens Canon EF 17-40 mm f: 1.4 USM is how most screwed. She sits at attention on the thread. Their shape is tulip-shaped.
The inside is they flocked with antireflective material. The same material can be found in the heart of Canon's lenses again.
For space-saving transportation in your pocket the lens hood can be the other way around placed.
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