Lesson Two Thursday Feb 10, 2005
Content
Describe how the digital camera works to capture images
1. View, critique and discuss student photos
2. The camera as a photo-electronic device to capture light.
The camera has 2 major functions: Focus and Exposure
FOCUS
3. Focal point in viewfinder.
4. Depth of focus
5. How to control auto focus
EXPOSURE
6. Exposure = aperture x shutter
amount of light that falls on the sensor is determined by the size of the lens opening, and the time it is open.
Too much light = overexposure, too little = underexposure.
7. The exposure meter - measuring the amount of light in the scene
All meters expose for an average amount of light (18% gray)
Most meters have a pattern of weighting the scene to calculate average.
See an example of how exposure meters work and check
this link for another view
8. Exposure controls - Shutter
measured in seconds, usually fractions e.g. 1/60, 1/125, 2, etc.
effect on blur, motion
Auto exposure - when it works, when it doesn't
How to control auto exposure
9. Exposure controls - Aperture
measured in f-stops, ratio of hole diameter to focal length f2.0, f4.0, f5.6, etc.
effect on depth of focus (see lecture 3 on focus control)
10. Exposure controls - ISO
ISO is the sensor's light sensitivity
Comes at a price in terms of more noise (lower signal to noise ratio)
Choose manual rather than auto ISO to control noise
11. Color Control - White Balance
light has a color temperature
can be seen on white walls
Students must email be an example of their own work for posting on the student photo page. Be prepared to describe the photograph and what it exemplifies.