Nikon D3100 help filming? Everything fine but?

I'm really happy with the pictures it takes, but filming?

it can film, very well. But only for like 10 - 30 seconds at a time?

its nothing to do with memory (even though i seriously need a bigger SD card),
after filming a 10 second video, it then lets me film another - so it can't be memory right?

i'm thinking it has something to do with the lens? The focus? When it's out of focus will it stop filming?
but the camera is perfectly still when i film, so it can't move to unfocus.

please help D: i'd really like to be able to film or longer? Sorry about all the question marks.

Unless you are using SDHC memory cards that are Class 10, the cameras buffer will fill and eventually the camera will shut off because the memory card can't keep up with the huge stream of data generated by shooting in HD

When shooting Full HD video, All CMOS sensored dSLR's shut off after about 30 seconds to two minutes or so. Why? CMOS sensors get hot when turned on for certain lengths of time.

Try shooting with the video at standard HD and you will see that the takes can be longer.

So, the answer is that your memory card can't read/write fast enough for full HD and that the sensor eventually gets to hot.

What can you do?

You can script your video and break that script down into a shooting script with scenes that are less that a few minutes.

The D3100 *records* video. You need a class 10 SD card in order to HD video.

You're really going to need lots help with that. This camera doesn't do film… In case you hadn't noticed… It records video. Say, do you know what film is? I suspect not.