I've been wanting to try a variable ND filter for a while, but the "best" ones are very expensive. When I found the Tiffens (around $99 US) and some positive reviews, I decided to give it a try. Currently listed on Amazon as a 2-8 stop filter (I swear it said 9 when I bought it.), I could only get good results unto 4.5 stops. I could get 7 at most, but there were issues. I tested this with a couple of controlled scenes to see how many stops I could get before it started to display the corner vignetting and X pattern that all variable ND filters eventually show. The filter has 6 marks between the max and min labels on the rotating section covering about 90 degrees of filter rotation. The transition from min to max is not consistent. At min, there is one stop of light loss. At mark 3 it is 2 stops; at mark 6 it is 4.3 to 4.5 stops. That's fairly linear, but then very small motions make a big difference in light cut off. At the max mark, it jumps to about 7 stops. Unfortunately, between mark 6 and the max mark, the corners start to darken. It is not too bad, but the change form 4.5 stops to 7 stops happens over a very narrow range, so it is difficult to control. It will get darker than 7 stops, but the X pattern makes the images unusable. There might be a sliver of 8 stops that isn't bad, but I could not find it. I still haven't taken any "real" pictures with it, but I'm not wowed. I'll admit, this may be normal behavior for VND filters. If so, I'm just glad that I didn't spring for one of the better ones to learn that it isn't what I was hoping for. in this age of solid ISO ranges in the cameras, I think I'd be happier with something like a 6 and a 10. If needed, I can fill in the range by raising the ISO.