I have a Canon 85mm f/1.4 that you can't always shoot full open on sunny days without overexposing the image. Having an ND8 filter to knock down the incoming light 3 stops is pretty much perfect to allow you to open up to your widest aperture and shoot.

On my picture above, you can see that the glass for this is pretty good. Ignore the focus (as the left photo was shot as f/1.4, the right at f/4), on my other pictures I cannot tell a difference in image clarity, even when pixel peeping. The two images were shot at 3-stops difference using my aperture and you can see the overall brightness is about the same (keep in mind the f/1.4 vignettes a bit due to my lens)-- so this is a true, ND8 filter. There is some minor color cast, but it's very minimal and Photoshop is happy to auto adjust that out anyways when you start editing your images.

This filter comes in a nice case and the filter is low profile (good new for wide angle lenses) with threads on the front of it if you need to stack another filter.

If this review ended here, I would give it 5 stars. Unfortunately the threads for attaching this filter to your lens are warped or poorly cut. I spent a good 2 minutes each time fiddling with it (spinning it backwards until it seemed like it dropped in, then tightening it, etc.) and it kept trying to cross thread. Once I thought I did have it lined up, it was rather stiff to turn and I don't know that I even got a full rotation out of it. I thought maybe I was just terrible at threading on filters, so I grabbed my B+W filter (brass threads)-- 5 seconds, straight on, tightened all the way, no problem. So I grabbed my Hoya filter (aluminum threads)-- 5 seconds, straight on, threaded all the way, no problem. The problem was not me or my lens, it's this filter.

Maybe 2 stars is a bit harsh, but when you're attaching this to the front of a $2K lens, the last thing you want to worry about it cross threading this , damaging your lens, or worrying about it coming off because it doesn't have full thread engagement. The glass on this filter is top notch, however I wish they would have taken the same care and produced threads with similar quality.