I recently recieved a Nikon N75 for a photo class I am enrolled in. Unfortunately, I only have one lense and that does not suit me very well because I like variety. I came upon a lense for $70 that is a Telephoto lense...The problem? I am unfirmiliar with the brand which is called Opteka. Does anyone have any experience with this brand? Is it good, is it bad? Any suggestions on good but inexspensice Telephoto lenses? Thanks!