Bests & Worsts Reviews from Amazon

Prior to buying this filter, I saw a few reviews on here saying they received a knockoff filter with poor performance. "No problem," I thought, and decided to buy used from a reputable seller on here, hoping to avoid the problem. But alas, I didn't. I somehow still ended up with a fake B+W filter. I got around to doing some tests (see the attached image) and you can see what I mean. My Tiffen polarizing filter performs great, blocking out the computer screens as expected. But when I put on the knockoff B+W filter, I see a HUGE drop in exposure. I didn't calculate exactly, but it seems like it darkens the image by 4-5 stops. And when I raised the exposure to match my Tiffen filter, I saw a very noticeable blue/purple color shift, which is most evident in the bottom left corner of the frame (where a daylight balanced LED is shining through the glass table). HOW TO TELL IF YOU'VE RECEIVED A KNOCKOFF FILTER: -The filter significantly lowers your exposure and/or adds an ugly color shift to your image (this is the most surefire way to determine if you have a fake) -The filter is lightweight (the real one is supposed to be brass, which is heavier than a typical cheap filter) -The filter has white printing on the front ring (the B&H product listing shows this filter with gold text, so I believe the real filter has gold text instead of white) Search for "B+W fake filter" online and you'll find an article on The-Digital-Picture which has more info on this. It says "In general, photographs of boxes and the text on the filter will not confirm a legitimate B+W product" so the most surefire way to determine if you have a fake filter is to test it on your camera like I did. My recommendation is to buy this filter from a reputable source like B&H until Amazon can get it together and remove the fake listings/sellers from this product page. Or you can get it here and risk having to return it. Just be cautious!