The exposure time usually I charge with an app on my Android device - just search for ND filters in the store looking for. The exposure time is increased by 1000 times the mean of a 1 / 20m is at a time 50 seconds. So you can get a strong flow effect in the water produce or allow people from places disappear in front sights.
The image quality, unlike inexpensive filters, hardly affected.
Why a sliding filter?
I opted for sliding filters, since I can use in many different lenses with different diameters this universally. In addition I have a filter holder and the appropriate adapters for the respective diameter. Also, it makes, particularly in such a strong gray filters, perfect sense, because the filter can be easily pulled out of the holder in order to focus. In the screw filters is relatively complex, since it must be screwed forever.
The processing and the accessories like a straightaway. Here, a microfibre cloth with the drops or dirt can be removed, the filter is protected by a rigid plastic case
