An image sensor, a mobile terminal, and an image photographing method are provided. A pixel array of the image sensor includes a preset quantity of pixel units. The pixel unit includes a first full-pixel dual-core focus pixel and a second full-pixel dual-core focus pixel. The first pixel is composed of at least one red sub-pixel, at least one green sub-pixel, and at least one blue sub-pixel. The second pixel includes at least one of a red sub-pixel or a blue sub-pixel, a green sub-pixel, and an infrared sub-pixel.