The filter is worthwhile, especially for the price! It optimizes my pictures and a quality image even in the processing. I knew from the outset that it saves me 3 f-stops, but now see the fast reached limits. In normal daylight with max. shutter closed are only max. Exposures of a 1/8 second possible. Although a certain amount of leeway, but not really enough for long exposures in daylight for example, flow movements represent smooth. But for that the filters can not help :) Of course I'm talking about more opportunities in the depth of field, but I had to buy a second filter for longer exposures. Only two filters together enable correct long exposures during the day.
Can also recommend an adapter ring for filters! So you can use the filter on several / all lenses. Works just fine with me.
