DVI at 7.5m is really pushing it, but it will depend on a number of factors:
1) The higher the resolution/refresh rate, the more likely you are going to see problems as you extend the cable length, so while 1024x768/60 Hz might be OK at 7.5m, you might start getting artifacts at a higher resolution.
2) Cable thickness. Look for cables with thicker (e.g., 24 ga. instead of 28) wires, which will help prevent signal degradation. I've seen a typical thin wire cable give problems even at 2m. (Note: so called "premium" cables aimed at the consumer market aren't necessarily thicker or better; look for more commercial-oriented cables.)
3) Adapters -- I'm not sure what type you're using, but try to use nothing. Every extra set of connections will degrade the signal further.
In the end, when you're stretching the limits, you just have to try it -- it will either work, or it won't. If the signal degrades, you'll start seeing obvious artifacts: shimmering pixels that might resemble snow on your monitor, or even shimmering lines of pixels, or just nothing if the signal is badly degraded. If you can't get it to work, a repeater is one option, though it will start getting expensive. You're better off just moving the equipment within 5 meters of each other.
1) The higher the resolution/refresh rate, the more likely you are going to see problems as you extend the cable length, so while 1024x768/60 Hz might be OK at 7.5m, you might start getting artifacts at a higher resolution.
2) Cable thickness. Look for cables with thicker (e.g., 24 ga. instead of 28) wires, which will help prevent signal degradation. I've seen a typical thin wire cable give problems even at 2m. (Note: so called "premium" cables aimed at the consumer market aren't necessarily thicker or better; look for more commercial-oriented cables.)
3) Adapters -- I'm not sure what type you're using, but try to use nothing. Every extra set of connections will degrade the signal further.
In the end, when you're stretching the limits, you just have to try it -- it will either work, or it won't. If the signal degrades, you'll start seeing obvious artifacts: shimmering pixels that might resemble snow on your monitor, or even shimmering lines of pixels, or just nothing if the signal is badly degraded. If you can't get it to work, a repeater is one option, though it will start getting expensive. You're better off just moving the equipment within 5 meters of each other.
