Image picking-up system, image capturing apparatus and electronic device

An image picking-up system comprising seven lens elements, the seven lens elements being, in order from an object side to an image side:

• a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, a sixth lens element and a seventh lens element;
• wherein each of the seven lens elements has an object-side surface facing towards the object side and an image-side surface facing towards the image side;
• wherein the first lens element has negative refractive power, and the object-side surface of the first lens element is concave in a paraxial region thereof;
• the image-side surface of the seventh lens element is concave in a paraxial region thereof and comprises at least one convex shape in an off-axis region thereof;
• wherein the image picking-up system further comprises an aperture stop, an axial distance between the second lens element and the third lens element is greater than an axial distance between the third lens element and the fourth lens element, a focal length of the image picking-up system is f, a focal length of the fifth lens element is f5, a maximum among refractive indices of all lens elements of the image picking-up system is Nmax, an axial distance between the aperture stop and the image-side surface of the seventh lens element is SD, an axial distance between the object-side surface of the first lens element and the image-side surface of the seventh lens element is TD, and the following conditions are satisfied:
• −1.0<f/f5<0.40;
• 1.60<Nmax<1.72;
• and
• 0.50<SD/TD<1.20.

An image picking-up system comprising seven lens elements, the seven lens elements being, in order from an object side to an image side:

• a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, a sixth lens element and a seventh lens element;
• wherein each of the seven lens elements has an object-side surface facing towards the object side and an image-side surface facing towards the image side;
• wherein the first lens element has negative refractive power, and the object-side surface of the first lens element is concave in a paraxial region thereof;
• the object-side surface of the seventh lens element is convex in a paraxial region thereof, and the image-side surface of the seventh lens element is concave in a paraxial region thereof and comprises at least one convex shape in an off-axis region thereof;
• wherein the image picking-up system further comprises an aperture stop, a central thickness of the seventh lens element is greater than an axial distance between the first lens element and the second lens element, a focal length of the image picking-up system is f, a focal length of the fifth lens element is f5, a maximum among refractive indices of all lens elements of the image picking-up system is Nmax, an axial distance between the aperture stop and the image-side surface of the seventh lens element is SD, an axial distance between the object-side surface of the first lens element and the image-side surface of the seventh lens element is TD, and the following conditions are satisfied:
• −1.0<f/f5<0.40;
• 1.60<Nmax<1.72;
• and
• 0.50<SD/TD<1.20.