Windows 7 Backup Compression

I'm running windows 7 pro, and am interested in using the win7 backup feature. My only caveat is the compression that will be used. I see no information on how I can specify the compression scheme of the backup like on other programs (ex. max. compression, normal compression). So mu question is... if anyone knows.... What kind of compression does the windows 7 backup program use? Does it always use the maximum compression? What compression rate can I generally expect (assuming a normal file - I'm quite aware that depending on the individual file it will get compressed only a certain amount)?

Thanks,
Dan