Tv max resolution/hz

[greaser]

What is the max resolution for a tv and refresh rate? I've been using 640 x 480 resolution. What is a safe limit?

[MonMotha]

For standard NTSC (not HD or ED), 525 lines at 59.94Hz or 60Hz vertical interlaced, 15.3-15.8kHz horizontal (it varies depending on who you ask and what TV you have, the spec says 15.73kHz if you do the math).  Many of those lines are blanked or reserved for sync.  480 visible lines is about right.  For PAL, 625 lines (again, fewer active), 50Hz interlaced vertical, about the same (15.5kHz or so) horizontal.  You can usually fudge things around 55-60Hz, 15-16kHz for NTSC and still not upset things.  640x480 would be the most optimal PC type mode, just remember to interlace it (this will not be an option on any normal GUI these days).  If you don't mind non-square pixels, 720x480 is usually still within the bandwidth of most TVs on anything but the composite input (this is also NTSC DVD resolution), and some (mostly HD capable anyway) can resolve up to 1280x480 (which is REALLY non-square).

If you have an "EDTV" (progressive) display, you can drop the interlace which will bump your horizontal up to 31kHz, standard VGA 640x480.  Note that if you're using the TV out feature on your video card, it's all being scaled and interlaced for you, but 640x480 or 720x480 is still optimal.

If you have an HDTV, you can hit a native mode for that.  720p is 720 lines (the ATSC spec asks for 1280 horizontal, yielding the same pixel aspect as 720x480 for 4:3 displays, and square pixels on a 16:9 display) @59.94 or 60Hz vertical, progressive, and 1080i is 1080 lines (1920 pixels horizontal, if you care), 59.94 or 60Hz interlace.  Many will scale just about anything down to standard NTSC up to their native mode (especially true of non-CRT technologies).