A first test of my copy showed that he indicated the extension factor 2-400 not quite at a focal length from 50mm small-screen equivalent of my Nikon P7100. It's more of 2.5-250, which corresponds to around 1.5-8 stops. The quality is good to satisfactory, while turning the adjusting ring it crunches ever easy, but it is easy and without hackeln, and wiggle also does nothing.
In my copy of the min and max markings voted not entirely, but which must be observed anyway, that the Max-position rather than in the middle of the "> max <" - is lettering, but next to it in the rectangular box to the right. For "> min <" also applies to the neighboring square. The actual position by about half a box-distance too far left to the maximum mark had slipped on my.
The step of ND2,5 - ND5 stretches over about half of the adjustment range, then it goes on quickly. The length of the rectangles seem to filter factor in the form of aperture values represent: An increase equivalent to about a factor of two, ie an aperture value. But this is just Pi times thumb so, the exact extension factor can be measured at best.
Unfortunately, the arrow marking the setting is present only once, and not 180 degrees opposite. So it can happen that all the way down when screwing lands, and you can hardly see the setting. In a pinch, you can paint on himself a, the filtering action should in any case continue to be the same 180 degrees.
Since the filter does not have fixed stops, you can turn it accidentally slightly above the minimum and maximum positions beyond. When Min-position that's not bad, it is then only a bit darker again. When Max first position against aberrations are produced: the edges are first bright, then a black, X-shaped cross in the picture. If you use the extension factor so full of the blind operation is difficult here. One should check the setting in the "Live View" or with sample recordings here.
Ever one summarizes easily by adjusting the filter disc, because it is set back inward. To avoid this, I would recommend this to extend to a step-up adapter or a small sunshade screen. Since the front filter thread is cut in the dial, you can turn in order then. It should be noted that the front filter thread a step to lose more so than here 55er. This is probably to avoid shadowing effects because quite thick filter.
A sun visor is also therefore makes sense because the filter is apparently not paid, and therefore could tend in backlight and side light incident to the formation of ghost form.
Positive is definitely that the loss of sharpness even fails somewhat less than by the built-in, switchable ND filter my Nikon P7100.
I have read in other reviews that this "X" is also seen ever before. This can probably already happen in very small wide-angle focal lengths something before the Max position, or if one of the filter plates is slipping. In addition to a production error this could happen even when you brush in a circular motion - here so I would be careful. The filter will still work, only the setting arrow is just in the wrong place. One can then but yes paint on a new ...
Conclusion: This filter has some handling difficulties, has apparently not paid and misses the specified setting range by about an aperture value. But since he is lonely favorable and produces quite sharp images, I am inclined to forgive him all that. Therefore 4 stars.
Now even instructions concerning the operation and the names of the extension factors:
1) This variable neutral density filters are basically comprised of two oppositely rotatable polarizing filters. Here, unfortunately, also results in a dependency between the filter position and the effect of certain polarized light, as with a simple polarizing filter. You can check this easily by placing the filter in front of a LCD monitor rotates (completely without changing the setting): Then there are two positions in which the image is black. To avoid this, or to deal with it in critical cases can, in fact, both filter plates would be mounted. It was probably omitted from handling and cost reasons, but that's all I know other Vario ND filters as well. However, I do not know if it the other manufacturers may succeed in mitigating the Abhängikeit through the use of circular polarizing filters on or off completely. Since my Hoya CPL changes with the circular side in front of a LCD display color when turning, I suspect that a dependency can never be completely avoided.
2) The filter has a low color distortion and little to no effect in the lower infrared. This is generally not a problem because modern cameras have a sufficiently strong built-in IR cut filter, and the low color cast is easily compensated for by the automatic white balance (it will be used!). But I also wanted to use it initially, in order to make with a Sony DSC-V3 in Night Shot mode in daylight infrared shots. In this mode, the camera works off the built-in IR-cut filter, but is automatically a minimum shutter speed of 1 / 30s at maximum aperture a, so possibly a gray filter is needed in addition to an infrared filter to prevent overexposure. Here was not enough in connection with a 720nm filter and the darkest setting out to achieve meaningful results, while the 55mm NDX8 then worked with a conventional Hoya HMC Neutral Density Filter.
3) The term of gray filters is partly confusing because ND2-ND400 here refers to the extension factor, ie, changing the exposure time. If a 1 / 2000s exposed without filters, so when ND 2 1 / 1000s would be necessary, and ND400 1 / 5s as 1 / 2000s * 400 = 1 / 5s. That would, in turn, about 8.5 f-stops. Other manufacturers call this extension values, however still with an X, so NDx2-NDX400 while values without X are graded there for the 10-he-powers of extension. Here would be eg ND0,3 = NDx2, ND0,9 = NDx8, and ND2,7 = NDX400
