1. A method for extracting depth information by a camera having a first lens and a second lens, comprising: photographing, by the first lens, a first image; photographing, by the second lens, a second image of a same scene; cropping a portion of the second image to make an image region acquired in the second image coincide with an image region acquired in the first image; down-sampling the first image to a resolution of the cropped portion of the second image if the first image is an image having a higher resolution than a resolution of the second image, wherein the resolution of the cropped portion of the second image maintains an original resolution of the second image; correcting the down-sampled first image to match the down-sampled first image to the cropped portion of the second image; and extracting a depth map from the corrected down-sampled first image and the cropped portion of the second image.