In the beginning I was just playing around and used the Av setting for night shoots, the results where pretty noisy. So how to get a nice clean nightshot?

For the best result you should set everything to manual and do the following:

-Set the right white balance, this will keep the colors looking cleaner
-Aperture, make sure it is as open as possible.
-Exposure, if you are shooting 25P set it to 1/50th
-ISO, above 1600 ISO it becomes a bit more noisy. ISO 6400 is too much. For some reason the Av setting will jump to 6400 pretty quickly.

Here is an example video that combines ISO 1600 and ISO 6400 so you can see the big difference this ISO jump makes.



So what about the kittlens?

If you want to shoot a lot in low light conditions you will have a bit or a problem, the Kitlens starts at F3.5 and zoomed in the aperture will be F5.6. This is one of the reasons people use prime lenses: you can pick up a reasonably prices 50mm F1.4 and shoot with 3x less light then the kitlens. Or simple put: the stuff you shoot at ISO6400 with the kitlens can be shot at ISO1600 with a F1.4 lens, or even ISO800.

This is a huge difference in quality, not just because you get less noise, but another important issue with high ISO: contrast. Any highlights wash out much quicker in higher ISO.

Can you get any zoom lenses that still work in low light?

Sure, check for F2.8 lenses, but they are expensive. Like the very nice 70-200 F2.8: it is F2.8 throughout its entire zoom range. And you pay the price for this.

If you are buying new stuff, make sure you check out the zoomrange and the aperture range. If you want to go cheap, the 28mm F1.8 is not bad, the 24m F1.4 is great but cost as much as the 7d. The 50mm F1.4 is very versatile, affordable and my personal favorite. But you will have to turn into a focusjockey to keep stuff in focus at F1.4 because there is no autofocus in video mode.