With a neutral density filter can be by turning the outer ring control the darkening thanks polarization principle. In particular, to film a filter is so outstanding.
I noticed is this:
1. When comparing the color fidelity of the different Abdunkelungsstufen noticeable that the image at low dimming is slightly yellowish. In the central position it is almost neutral in color. Upon further darkening the color impression is increasingly blue.
These problems can be compensated in modern cameras thanks to manual white balance.
2. Also at high darkening the automatic focusing by the camera is possible.
3. To note also that comes in strong darkening lost the sharpness of the image. But this is a general problem.
I'll keep the filter and use on location to reduce the incidence of light in order to influence the depth of field.
For this price, I can only recommend the ND filter.