2. Camera Education Department (RSS) December, 1999 Physics

3. Body Lens system

4. Lens Focusing ring Aperture Shutter Film Structure

5. A camera is a light-tight box in which a convex lens forms …. Film A real & inverted image Object

6. Focusing The focusing ring is turned to move the lens forwards or backwards. Focusing ring (What is the range of the object distance?)

7. Focusing ring moves out Short object distance Long image distance Near Object

8. Focusing ring moves in Long object distance Short image distance Far Object

9. Aperture( f-number) Aperture controls the amount of light entering the camera. Aperture The size of aperture is controlled by the diaphragm. f-number selector

10. The smaller the f-number, the larger the aperture. f =11 f = 8f = 5.6 f = 4f = 2.8

11. Shutter speed When the button is pressed, the shutter opens and shuts quickly to allow a small amount of light into the camera. Shutter speed selector 125 stands for 1/125 s Shutter button What is the fastest shutter speed of this camera?

12. A fast moving object requires a shorter shutter speed otherwise it will appear blurred. The night scene should be taken with a slow shutter speed. If aperture is doubled in area, the shutter speed should be halved.

13. Lenses with different focal lengths (f) Wide-angle lenses f = 20 - 35 mm Normal lensesf = 50 mm Moderate Telephoto lenses f = 85 - 150 mm Telephoto lenses f = 150 - 500 mm Zoom lensesAdjustable f ( e.g. from 28 to 135 mm)

14. The longer the focal length, the greater the image. F F Object image

15. 300 mm 8° 105 mm 23° 45° 50 mm 75° 28 mm Angle of view Focal length The longer the focal length, the narrower the angle of view.

16. Comparison between an eye and a camera EyeCamera film pupil invert & real image The ciliary muscles adjust the shape of the lens to focus retina aperture real & inverted image Adjust lens-to film distance to focus

17. ～ END ～