 document stands (more often called document cameras) provide for standard resolution graphics exchange. Document cameras marry a small color video camera to an overhead projector. The camera points down at a baseboard with lighting to display physical objects, instructor's notes or transparencies, etc. The capabilities of document cameras differ. Most systems offer single-chip CCD cameras. A three-chip CCD camera is required in cases where end-users want very high-quality graphics (remote inspection of parts, engineering applications, etc.). Some document cameras both focus automatically and offer manual adjustments. Others offer manual adjustments only. Controls are sometimes included as part of the video communication system's operator console. More often the user must make adjustments at the document camera itself. Using a document camera or other image capture techniques, codecs may also deliver high-resolution display of freeze-frame graphics. Resolutions widely vary, from 2X. Picture formats generally include JPEG, TIFF (Tagged Image File Format) or TARGA (Truevision Advanced Raster Graphics Adapter). Graphics systems often comply with the ITU-T's H.320 Recommendation H.261 Annex D that doubles the CIF horizontal and vertical resolution for television-quality graphics. Most group-oriented systems provide the ability to create and store images as slides. Program files can be retrieved during a videoconference and used to make presentations. Participants can view these visual materials and annotate them independently. Collaborative tools (which let participants share application control) vary in power. Almost all are now based on the ITU-T T.120 Recommendation. Even when a video communication system does not integrate the ability to create, store, and retrieve documents and images, it can usually be equipped with a T.120 outboard system. This delivers similar functionality-at additional cost. Group Systems Figure 13-6. Workgroup Application (courtesy of Polycom). Document and graphics subsystems vary in soph