The director of photography, commonly referred to by the initials DP–or DoP in some european countries, is responsible for the framing and overall look and feel of the shots in a film. A DP will also be responsible for technical aspects of the shoot, such as lens choice, filters, exposure, lighting, gels, and the on set team responsible for making these adjustments.
On smaller shoots the DP may actually operate the camera; on larger shoots will oversee a crew which includes a camera operator.
Ultimately it’s the DP’s job to realize the creative vision of the director.