A fundamental accessory for anyone who wants to shoot movies with a Mini 5, ND filters are already included at the factory but are of low levels, this ND filter (acronym for Neutral Density) integrates those already present at the factory, extending the functionality up to 9 stops of reduction (equal to ND512). An ND filter does not change shades or colors, but simply darkens the image that hits the sensor. This reduction in brightness forces the sensor to work either at higher ISO, or (what we need) to extend exposure times. To have a cinematic effect (where the shooting is therefore very smooth) to make it very short, the opening time of the sensor must be equal, at most half, of the framerate chosen for the video. Practical example: video at 30FPS (30 frames per second), the aperture of the single frame must be from 1/30 to 1/60 of a second to appear very smooth. Without these filters, for cameras with a fixed diaphragm aperture, it is impossible to achieve such opening times, as often, depending on the ambient light, more than 1/320 1/500 can be easily worked. This means that our videos will appear “snappy”, and the only way to make them smoother is to increase the framerate (bringing it to 60fps). This K&F filter is extremely useful because it helps to reduce with important stops (from 5 to 9, therefore for extremely bright environments), but above all in a dynamic way: we do not have to replace the filter but we simply have to rotate the ring dynamically to obtain the desired result. In the field, all we have to do is apply the filter, frame more or less the area we intend to film and rotate the ring to obtain the desired result. Since we don't have control over the diaphragm, we'll have to keep the aperture fixed (following the example from before, setting 1/30 aperture), keep the ISOs automatic and adjust the ND filter stop ring until the ISOs are around 200-300, this to have a bit of “play” even if the filter set is not sufficient, framing even brighter areas. By doing so, our videos will be properly exposed and perfectly cinematic. The quality of this filter is high: the body is made of plastic to save weight, but the attachment to the gimbal is perfect and solid. The lens does not have the slightest distortion, the ring is “weighted” just right, it doesn't take too much effort to turn it but at the same time it's firm enough not to move inadvertently. It comes in a practical box to carry it in the bag, and a cloth to clean it if necessary. Really a great product, in my opinion sold at a price in line with its quality.