nd from the videophone applications; for the same field of view, the focal length display. When the camera is mounted in the plane of the display, the of the lens is reduced to 5mm to 5.5mm. options are to position the camera centrally above the display or on Fixed focus lenses are to be preferred since, particularly in video- one side of the display on the anticipated eyeline of the displayed phone applications, auto focus lens operation in following small head and shoulders picture, i.e. slightly above the centre line. movements will result in picture changes which then have to be For a fixed viewing distance, the eye contact angle is minimised coded for transmission, thereby reducing the efficiency of the cod- by positioning the camera above, and as close as possible to, the ing operation. Even for the most critical fixed focus application, e.g. display, and by using the smallest acceptable display size. However, a videophone terminal 70cm from the user and a 0.5 inch CCD despite being a less than optimum arrangement, there are a number camera with 8mm focal length lens and the aperture open at f2.0, of videophone terminals (usually the smaller ones) with the camera the subject will be in focus over the range 40cm to over 3m for a positioned at the side. One of the reasons the industrial designers QCIF resolution picture (176 picture elements per line), and over concerned give for preferring this arrangement is that a camera at the range 50cm to over 1m for a CIF resolution picture (352 picture the side is less obtrusive and dominant than one positioned centrally elements per line). above the display. Further work is required to determine user pref- Videophone and videoconference terminals in a standard office erence. environment need to operate satisfactorily in lighting conditions A European standard (ETSI, 1991) is in preparation which ad- which range from bright sunlight to poor artificial lighting. It is the dresses these and many other design aspects of videophone termi- illumination of the user's face t