1. Lenses
Are classified
by their
Focal Length

2. Focal Length The distance from the optical center of a lens
to the front surface of
the imaging device.

3. Short Focal Length = Wide Field of View (Wide Angle) Long Focal Length = Narrow Field of View (Narrow Angle)

4. Prime Lens: one set focal length. Zoom Lens: variable focal length.

5. Iris
Adjustable lens opening mechanism

6. Aperture
Hole in center of iris
Measured by f-stops

7. Aperture
Can adjust larger or smaller depending on the amount of light

8. F-stop Scale Indicates how open or closed the iris is.
The larger the F-stop number, the more closed the iris is, therefore the less light enters the lens.

9. Aperture
What type of aperture opening would you use for a sunny day?

10. Aperture
What type of aperture opening would you use for a dark room with only a candle for light?

11. Auto Iris Many cameras have auto iris
Adjusts automatically depending on setting

12. Focus When subject in viewfinder is sharp and clear
Zebra Stripes: Indicate overexposed areas of the frame to assist in correcting exposure.