Always use a lens hood (the optional removable flange that sticks out on the front of your lens). Indoors, outdoors; day, night: always.
The obvious reason is to decrease the kind of flare you see here, on the right:
But the hood also provides:
- More subtle contrast enhancement
- Damage prevention
- Prevention of dirty lenses
That’s why you always use one, and it is why expensive lenses come with one.
Make sure you use the right hood for your lens. And if a lens has a hood, use it. It can cast a circular shadow when you are using your pop-up flash, but you should not be using that flash anyway.
I wish you all a very happy New Year tomorrow, full of joy – including the joy brought by increasing photography skills. And note that tomorrow’s post may be late: I intend to sleep in!