Focal length refers to a lens's magnification strength, with shorter focal lengths providing a wider angle of view. Depth of field is the range of distance in a scene that appears in focus, and it is controlled by aperture size, focal length, and a subject's distance from the camera. A low aperture, long focal length, or closer subject position results in a shallower depth of field and less focus range, while a high aperture, wider lens, or farther subject provides a deeper depth of field and more focus range.

1. Optics and Depth of Field

2. Your Lens Your lens is made up of curved glass that is moved when you focus and zoom

3. Focal Length Focal length refers to the strength of magnification by a lens

4. 24mm 50mm 200mm 800mm

5. Focal Length and Angle of View The Shorter the Focal Length the wider the angle of view

7. Other features of focal length Short Focal length = wide angle Wide angle lenses tend to distort objects especially if they are close to the lens Long focal length tends to compression image

8. Wide Angle Distortion

9. Wide Angle Distortion

10. Long Focal Length/Telephoto Compression

11. Telephoto Compression

12. Special Lenses

13. Tilt Shift Lens

14. Tilt Shift

15. Tilt Shift

16. Lensbaby

17. Fisheye

18. Fisheye

19. Depth of Field The portion of a scene that appears sharp in the image A lens can precisely focus at only one distance, but the decrease in sharpness is gradual on either side of the focused distance Not easily perceived by the human eye

21. Long/Deep Depth of Field Shallow Depth of Field

22. Depth of Field is Controlled by Three Things Aperture Focal Length-zoom Closeness of subject to camera

23. Controlling Depth of Field with Aperture A low aperture (1.8 to 5.6) gives you low.short/shallow depth of field A high aperture (11-32) gives you a long/deep depth of field

24. F 3.5 F 22

26. Controlling Depth of Field with Focal Length Longer lenses tend to give you a shorter depth of field resulting in blurrier backgrounds Wider lenses are better at keeping more depth in focus

28. Controlling Depth of Field with Proximity to Subject Similarly, the closer you are to the object the less depth of field will be present This is the same idea as focal length

29. More Examples

30. DOF

31. Low DOF

32. Low DOF

33. Low DOF

34. Low DOF

35. Low DOF

36. Long DOF

37. Long DOF

38. Long DOF

39. Long DOF

40. Long DOF