Photographing system, image capturing unit and electronic device

A photographing system comprising seven lens elements, the seven lens elements being, in order from an object side to an image side:

• a first lens element having positive refractive power;
• a second lens element with negative refractive power having an image-side surface being concave in a paraxial region thereof;
• a third lens element having an object-side surface being convex in a paraxial region thereof and an image-side surface being concave in a paraxial region thereof;
• a fourth lens element having an object-side surface being convex in a paraxial region thereof and an image-side surface being concave in a paraxial region thereof;
• a fifth lens element;
• a sixth lens element;
• and
• a seventh lens element having an image-side surface being concave in a paraxial region thereof, wherein at least one of an object-side surface and the image-side surface of the seventh lens element has at least one inflection point;
• wherein there is an air gap in a paraxial region between every adjacent lens element of the first lens element, the second lens element, the third lens element, the fourth lens element, the fifth lens element, the sixth lens element and the seventh lens element, a focal length of the photographing system is f, a focal length of the first lens element is f1, a focal length of the second lens element is f2, a focal length of the third lens element is f3, a focal length of the fourth lens element is f4, a focal length of the fifth lens element is f5, a focal length of the sixth lens element is f6, a focal length of the x-th lens element is fx, and the following conditions are satisfied:
• |f1|<|fx|, wherein x=2, 3, 4, 5, 6;
• and
• |f/f3|+|f/f4|+|f/f5|<1.5.