Practical Computer Vision with SimpleCV

Appendix B. Cameras and Lenses

Chapter 5 discussed the importance of lighting in a vision system. Of course, even the best lighting system will run into problems if the system is using the wrong camera. This appendix provides a brief introduction to some of the issues when choosing a camera. It covers:

• Basics of digital cameras

• A background on lenses

Cameras and Digital Sensors

Cameras have sensors that measure incoming light levels and then map that light onto a grid to form an image. Before digital photography became dominant, this process was done chemically, where the chemicals on the film would react to the light coming through the lens. Today, digital cameras have replaced chemicals with millions of little sensors that detect incoming light.

There are two commonly used digital light sensors: Charge Coupled Device (CCD) and Complementary Metal Oxide Semiconductor (CMOS):

• CCD is the most commonly used sensor in digital cameras. As a general rule, they create good quality, low noise images. However, they tend to require more power, making them less popular for cell phones, tablet computers, and other portable devices.

• CMOS uses less power than CCD. This means they are rapidly gaining in popularity as cameras are included in many battery powered devices. However, CMOS tends to result in lower quality and higher noise images. In addition, they are less light sensitive, which means they do not work well in low-light conditions.

Light sensors are color blind. To create color, light must ...