Is the lens of the camera as long as possible?
When shooting stars, the moon and very distant scenes, the longer the better, the more able to play a smaller perspective imaging function. But to shoot near the scenery, the collective photo and other large viewing angle of the scene, it is necessary to play a wide-angle lens. So that the length of the camera lens focal length and the subject matter of the shooting.
The focal length of the camera lens is related to the subject matter of the shot, and it is not always longer.
However, the longer the focal length of the lens the greater the color difference, the more difficult to correct, consume more materials, the higher the price this is the fact.