An optical photographing system includes eight lens elements which are, in order from an object side to an image side along an optical path: a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, a sixth lens element, a seventh lens element and an eighth lens element. Each of the eight lens elements has an object-side surface facing toward the object side and an image-side surface facing toward the image side. The object-side surface of the third lens element is concave in a paraxial region thereof. The fourth lens element has positive refractive power. The fifth lens element has positive refractive power. The sixth lens element has positive refractive power. The seventh lens element has negative refractive power, and the image-side surface of the seventh lens element is concave in a paraxial region thereof.