TOEFL · Section 5

Lecture Pinhole Camera

Now, when you think about a camera, you probably think the most important feature of a camera is the lense,

Level: B2 · 61 sentences

Transcript

1. Now, when you think about a camera,
2. you probably think the most important feature of a camera is the lense,
3. but back then there was no lense.
4. So the camera must use different type of technology to take pictures.
5. The very first "camera" makes use of a pinhole to project the image
6. but the resulting projection was upside down.
7. Because it makes uses of a pinhole, it is known as pinhole camera.
8. So. as I just said,
9. a pinhole camera is a simple camera without a lens
10. and with a single small pinhole....
11. It really is just a light-proof box with a small hole in one side.
12. Light from a scene passes through this single point
13. and projects an inverted image on the opposite side of the box.
14. Because a pinhole camera requires a lengthy exposure,
15. its shutter may be manually operated, as with a flap made of light-proof material to cover and uncover the pinhole.
16. Typical exposures range from 5 seconds to several hours.
17. Can you really imagine having to wait hours for a picture?
18. It seems so strange now considering we can snap a picture and see it immediately in a screen at the back of a digital camera....
19. Let's be real for a minute,
20. with the long exposure time and our fast paced world,
21. is there really a need for these types of cameras?....
22. The answer is yes, and this is why...
23. the most common use of the pinhole camera is to capture the movement of the sun over a long period of time...
24. and this type of photography is called solargraphy.
25. The image may be projected onto a translucent screen for real-time viewing
26. which is popular for observing solar eclipses,
27. that way you are not harming your retinas looking directly at the sun.....
28. Or, to be a bit more technical...
29. Pinhole devices provide safety for the eyes when viewing solar eclipses
30. because the event is observed indirectly.
31. The diminished intensity of the pinhole image being harmless compared with the full glare of the Sun itself.
32. Okay!
33. So we know a few more things about this camera,
34. but where did it start?
35. As in who created this neat little contraption?
36. Ibn al-Haytham, way back in the 10th century
37. wrote about naturally-occurring rudimentary pinhole cameras.
38. For example, light may travel through the slits of wicker baskets
39. or the crossing of tree leaves.....
40. If you think about it, the circular dapples on a forest floor, actually pinhole images of the sun,
41. can be seen to have a bite taken out of them during partial solar eclipses
42. opposite to the position of the moon's actual occultation of the sun
43. because of the inverting effect of pinhole lenses...
44. It's neat, right?
45. A natural pinhole camera, indeed.
46. Alhazen published this idea in the Book of Optics in 1021 AD.
47. He improved on the camera after realizing that the smaller the pinhole,
48. the sharper the image, though the less light.
49. He provides the first clear description for construction of a camera obscura......
50. So next April, when World Pinhole Day is held on the last Sunday,
51. you can tell people exactly why it is being celebrated.
52. Today we are going to discuss a camera
53. that you can not only make from virtually anything but it actually works....
54. Sounds a little crazy I am sure, but relax
55. and let's take a peek into the world of pinhole cameras.....
56. A pinhole camera really is one of the simplest ways to get involved with and enjoy photography.
57. The pinhole camera has existed for more than 500 years
58. and may even have its place in ancient history....
59. Totally different from the cameras we use today,
60. it requires no lenses.
61. Pinhole cameras are also a great way to introduce little kids to the joy of photography and the basics of optics.