Filevault and how to disable

I have a question regarding Filevault. I've decided that I don't want to use Filevault anymore. I tried to turn it off but I don't have enough hard drive room to decrypt all of my data on my hard drive. I have a lot of pictures and movies store on the hard drive. Can I move all of my media to an external HDD and then disable Filevault and bring them back onto the iMac's HDD? If so, how?