Originally posted by GLXLR I bought the cheap 67mm Crystal Optics set for about $15. Will they degrade the quality I get out of my 50-135mm? >.<
If cheap means uncoated and therefore low % light transmissions and more flare then yes, it will noticeably degrade the IQ. On the other hand, if you only take your pics for yourself and the filter is for protection, take some pics under harsh lighting and controlled repeatable circumstances, with and without the filter. If you can't see any difference then does it matter which filter you use? You are the only person that has to be happy.
Even the most expensive filters get in the way of SOME light. I refer you to the link posted in this thread by JEM that has a very technical review and bottom line value for the price for 20 UV filters.