You can cut up and use a sprite bottle as a plus filter on your lights. Just be careful with tungsten lights because I'm not sure how much heat it can take but it's perfect for fluorescent and LED lights like the one I have in the picture.
Recently Full Sail had an awesome Hall of Fame event in which they brought back successful industry professionals to talk about several topics. They recorded those seminars and posted them on their youtube channel. I'd suggest that you check out a couple of them if you have the time. They are definitely worth watch. I've embedded a couple interesting ones.
The Importance of Collaboration in Filmmaking includes Full Sail Hall of Fame Members such as Hunter M. Vai A.C.E. (Editor on shows like the Walking Dead) and Darren Lynn Bousmen (Director of Saw II, III, IV)
Video Review- link to sharpness test - http://petapixel.com/2014/12/27/comparing-optics-40-yongnuo-50mm-f1-8-125-canon-50mm-f1-8-ii/
Zachary Will is an Award-Winning Filmmaker creating short films and content for the Internet as the owner of Riverside Studios. He has a Bachelor's in Film from Full Sail University. He has worked on productions for companies like Webmd, Sears, Home Depot, Six Flags and more!
"the trick is to never give up... I think the secret of success is not how little you get knocked down but how often you get back up." - Gareth Edwards