Night scenes can be difficult to expose accurately. This is partly because there will often be large areas of darkness in the scene, and partly because different exposures can give equally good results.
This is the time to move away from the auto options of your camera and set the manual (M) shooting mode. When you do this, the exposure compensation scale becomes a manual exposure scale. If you adjust the shutter speed, aperture and ISO value until the index mark is at the zero (centre) point of the scale, you will have the same exposure level as the camera would set.
To start with, take a picture using the recommended exposure. Now you can adjust one of the exposure values - usually the shutter speed - and take another picture to see if this improves the image. In only a few shots you should obtain an image you like. Do not stop at this. Keep experimenting with different exposures to see if there are other pleasing results.
Museum of Islamic Art, © Rhandy Pelaez 2010, Canon EOS 550D
You can set exposure times of up to 30 seconds on your EOS. The 'Bulb' (B) mode lets you take exposures for much longer. How to set 'B' mode varies from model to model, so check your Instruction Manual for exact set-up details.
When you press and hold the shutter button in 'B' mode, the shutter will open and stay open until you release the button. A remote switch will allow you to lock the shutter open so that you do not have to keep the button depressed during the long exposure.
'B' mode is good for photographing star trails in the sky at night - the stars appear to move relative to the earth and draw circular paths in the sky. Long bulb exposures can also be good for photographing scenes using the light of the moon.