S-video output resolution

Question

I have a a mini-DVI to component/s-video adapter on my Macbook. I connect to a projector using the s-video cable. I did not expect this to be as clear a picture as direct VGA connection but it is much worse than I expected. The projector picture is noticably lower resolution than the SD digital TV tuner or DVD player that uses the same s-video cable.
I have set the display resolution to the maximum available (1024x768) but it does not seem to be using this resolution. The other choices under display preference are no better.
It looks like I will need to use the VGA adapter and cable for decent quality but that is going to be a nuisance with cables.

Answer 1

Due to the way an S-video signal is generated, the maximum resolution is about 640 x 480 pixels. You can output higer resolution to the S-video connector, but that resolution can not be meaningfully processed by a television set; the higher frequency components will be averaged together into a fuzzy low resolution display. The low resolution is a result of he way the S-video signal is composed and the timing constraints of NTSC or PAL video systems.
To get decent quality, you really need to use a component source such as a VGA cable that can send data at substantially higher data rates. S-video has a video bandwidth of about 4.5 MHz, while VGA bandwidth is 80 MHz or higher and is not constrained by NTSC or PAL timing.
Most CRT televisions usually don't make very suitable computer displays (unless the are designed with a VGA component input). The high voltage supplys of TVs aren't are closely regulated as computer monitors and the result is blooming, color bleed and positional jitter. Recall that TVs re typically intended to be viewed at a distance of a meter or more, while computer displays are often viewed at less than a meter. The relatively poor quality of an average TV isn't noticable at typical viewing distances, but looks terrible for computer output. Of course, high definition television has changed the rules, and high def TVs often double as pretty good computer monitors when fed with a VGA (or DVI or HDMI) signal.
I teach a communications systems course, and one of the things we study is television. As an exercise, we considered a 50 inch diagonal measure 16:9 aspect ratio screen. At 3.5 meters (about 10 feet), the apparent picture quality of a 720p and 1080i picture is the same to a person with average visual acuity - so unless you like to sit close to your TV, you can save cost by buying a 1376x768 pixel screen instead of a 1920x1080 screen. I have a feeling in the next year or two all screens sold will probably be 1920x1080 (or more) anyway, so above point may become moot.
Bill