Photographing optical lens assembly, image capturing unit and electronic device

1. A photographing optical lens assembly comprising eight lens elements, the eight 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, a seventh lens element and an eighth lens element, and each of the eight lens elements having an object-side surface facing toward the object side and an image-side surface facing toward the image side;

wherein a total number of lens elements in the photographing optical lens assembly is eight, at least one of the object-side surface and the image-side surface of the seventh lens element is aspheric, the image-side surface of the eighth lens element is concave in a paraxial region thereof, the image-side surface of the eighth lens element is aspheric and has at least one inflection point, and there is an air gap in a paraxial region between each of all adjacent lens elements of the photographing optical lens assembly;

wherein the photographing optical lens assembly further comprises an aperture stop; a focal length of the photographing optical lens assembly is f, an entrance pupil diameter of the photographing optical lens assembly is EPD, an axial distance between the aperture stop and the image-side surface of the eighth lens element is SD, an axial distance between the object-side surface of the first lens element and the image-side surface of the eighth lens element is TD, and the following conditions are satisfied:

f /EPD≤2.50; and

0.70< SD/TD< 1.10.

2. The photographing optical lens assembly of claim 1 , wherein the fourth lens element has positive refractive power, and the image-side surface of the fourth lens element is convex in a paraxial region thereof.

3. The photographing optical lens assembly of claim 1 , wherein the seventh lens element has positive refractive power.

4. The photographing optical lens assembly of claim 1 , wherein the object-side surface of the sixth lens element is concave in a paraxial region thereof.

5. The photographing optical lens assembly of claim 1 , wherein an axial distance between the object-side surface of the first lens element and an image surface is TL, the entrance pupil diameter of the photographing optical lens assembly is EPD, and the following condition is satisfied:

1.5< TL /EPD<4.0.

6. The photographing optical lens assembly of claim 1 , wherein the focal length of the photographing optical lens assembly is f, a curvature radius of the image-side surface of the eighth lens element is R16, and the following condition is satisfied:

0.3 <f/R 16<5.0.

7. The photographing optical lens assembly of claim 1 , wherein a focal length of the first lens element is f1, a focal length of the second lens element is f2, and the following condition is satisfied:

−1.0 <f 1 /f 2<0 or 0 <f 1 /f 2<0.7.

8. The photographing optical lens assembly of claim 1 , wherein the focal length of the photographing optical lens assembly is f, a focal length of the eighth lens element is f8, an axial distance between the object-side surface of the first lens element and an image surface is TL, a maximum image height of the photographing optical lens assembly is ImgH, and the following conditions are satisfied:

−1.26 ≤f/f 8≤−0.49; and

TL/ImgH< 2.1.

9. The photographing optical lens assembly of claim 1 , wherein a central thickness of the seventh lens element is CT7, a central thickness of the eighth lens element is CT8, and the following condition is satisfied:

0.71 ≤CT 7 /CT 8≤2.39.

10. The photographing optical lens assembly of claim 1 , wherein a maximum value among axial distances between each of all adjacent lens elements of the photographing optical lens assembly is ATmax, a maximum image height of the photographing optical lens assembly is ImgH, and the following condition is satisfied:

ATmax/ ImgH< 0.30.

11. The photographing optical lens assembly of claim 1 , wherein the focal length of the photographing optical lens assembly is f, the entrance pupil diameter of the photographing optical lens assembly is EPD, a curvature radius of the object-side surface of the sixth lens element is R11, a curvature radius of the image-side surface of the sixth lens element is R12, and the following conditions are satisfied:

f /EPD≤1.95; and

−2.5<( R 11 −R 12)/( R 11 +R 12)<0.80.

12. The photographing optical lens assembly of claim 1 , wherein the image-side surface of the eighth lens element has at least one non-axial critical point; a maximum effective radius of the object-side surface of the first lens element is Y11, a maximum effective radius of the image-side surface of the eighth lens element is Y82, and the following condition is satisfied:

0.20 <Y 11 /Y 82<0.70.

13. The photographing optical lens assembly of claim 1 , wherein at least one of the object-side surface and the image-side surface of the seventh lens element has at least one non-axial critical point.

14. An image capturing unit, comprising:

the photographing optical lens assembly of claim 1 ; and

an image sensor, wherein the image sensor is disposed on the image side of the photographing optical lens assembly.

15. An electronic device, comprising:

the image capturing unit of claim 14 .