Light is thoroughly important when taking photos but not when it comes in from all sides. To prevent such things occurring all you need is a lens hood that blocks light coming in from the side. This one here has a matt-finished inner surface which avoids reflections.

 

• Folding rubber lens hood blocks incident light from the side in any desired position
• For standard lenses (from focal length of 45 mm) and digital cameras with internal thread (screw-in mount: diam. 40.5 mm)
• Allows a 40.5 mm filter to be attached to the lens hood
• The inner surface of the lens hood has a matt finish to prevent reflections