the file size of a recorded video is mostly dependant on three factors.
1. The complexity of the footage
For example, recording a still image takes up almost no space.
2. The resolution of the recording
The more pixels have to be stored, the greater the file size.
3. The codec you encode your footage with
The codec is the one that does the compression of the recorded footage. The more it compresses your footage, the smaller the file size gets and usually the more the quality suffers.
You can find a list of video and audio codecs you might want to use over here.
I wouldn't recommend playing with the Quality setting too much, because setting it between 80 and 90 usually has the best quality-file-size ratio.
I've uploaded an attachment showing how to change the codec (there are different ones for AVI and MP4)
I hope I was able to help you.
Thank you for reading my post. I hope you understand my "English".
I'm the German translator for some of Bandisoft's products and websites
(mostly Bandicut and Honeycam).