Canon PowerShot 350 Service Manual - Page 12

Part 1: General Information 1.2 HIGH IMAGE QUALITY The world's first CCD-equipped consumer camcorder had a resolution of 180,000 pixels (NTSC). In the years that followed, the CCD's pixel count kept increasing until it exceeded 400,000 in 1987. Since 400,000 pixels were adequate for motion picture quality on a TV set, the pixel count stopped increasing. Instead, the CCD size started to get smaller. Today, 400,000 pixels can fit on a CCD one-sixth the size of a typical CCD made in 1987. When the image is moving, the image quality lOoks good with this number of pixels. However, if you stop the videotape and look at a single frame, you will notice the low image quality. It is mainly because the eye perceives image quality differently for moving and still images. The human eye is less critical in the case of motion pictures. Camcorders take advantage of this fact. Thus, in the case of still cameras (including digital ones), an absolutely high image quality is required, unlike camcorders. High image quality hinges on many elements. They include the following: 1. Resolution 2. Color reproduction 3. Tonal range 4. Dynamic range 5. Distortion (jitter) 6. Suitability for visual perception Table 1-1 shows the means for obtaining high image quality for image input (camera) and image output (printer). Table 1-1 Image Quality Improvement Parameter Camera Printer (Ink jet) Resolution • High-resolution lens • CCD with higher pixel count • Optimize optical low-pass filter • Higher head precision • Finer ink droplets • Improve color filter's spectral character Color reproduction • Optimize color signal processing • Incorporate CMS circuitry • Optimize signal processing • Improve ink and paper • Incorporate CMS circuitry Tonal range • Increase A-D converter bit count • Dot diameter control Dynamic range • Improve CCD structure • Improve signal-to-noise ratio • Higher ink OD • Improve paper Distortion (Jitter) • Improve signal-processing circuit linearity • Improve signal-processing circuit linearity • Improve paper feed and ink ejection mechanism precision Visual perception • Optimize signal processing suitability • Optimize signal processing • Improve apparent image quality Once upon a time, cameras were called precision instruments. Their development required sophisticated optical , control, precision manufacturing, and other technologies. However, as key technologies shifted to circuitry and large-scale integration for still cameras and especially camcorders, cameras increasingly fell into the domain of electrical appliance companies. Digital cameras do require large-scale integration technologies, but they also require "image quality technology'. This is where Canon outshines the electrical appliance companies. It is not something that is easily obtained through computer analysis. It is obtained through long years of experience making good pictures. Since its founding 60 years ago, Canon has grappled with the question of how to take good pictures. While pursuing this end, it has accumulated a enormous amount of know-how in the imaging field. This know-how is now an Important Intangible Asset for the company. Canon's digital cameras embody this asset. 1-2