A neutral density (ND) filter reduces the amount of light entering your lens. Since photographers usually want more light, some lighting sounds blocked the sounds like a crazy idea. But for long exposure photography, when you want to objectively want to introduce motion blur, or when you require long shutter speed for video or flash photography, neutral density filters are often required. In this article, I will review such a filter: K & F Concept Nano-X variable 1-9 stop ND filters. It is a relatively inexpensive filter, priced at $ 73 in a 58 mm size that I tested.
Build quality and features
The K&F concept 1-9 stop nano-X is made of two pieces of glass roaming against each other. As a variable ND filter, it allows you to control the level of light decrease, which is proportional to the difference in the angles of polarization of two glass elements.
This special filter comes in a good bag, and it has a small ribbon on that side that helps in extracting the filter. It is a much more practical solution than some cases of plastic that come with other filters that are often open. In the area, it can be difficult to flicker the filter, so I appreciated this feature.
The density of the filter is easy to adjust, and can be done with the orange tab that sticks out of the side. If you have gloves, it is a great way to turn on the filter, but it prevents you from using a traditional lens hood. However, if you like to use a hood, the orange tab can be taken with a small tacccish. The filter itself consists of a small arrow that pointed to a graduate on a scale, making it easier to adjust the level of darkness.
Viewing performance
Many filters add a bit of additional vignates, which is usually very easy to correct in the post. I tested the filter at 14 mm and 45 mm on the Olympus 12–45 mm F/4 Pro Lens, so that a thick idea of vigning could get, and I also compared the filter against bare lens. By dividing the glow of a photo with the filter and without a photo, I can find an estimated idea of wigting of this filter. To see if the density of this variable ND filter matters, I tested it on both 2-stop and 5-stop density:
This test is very informal, but shows that the vignating is minimal at 45 mm (90 mm FF equivalent), and a little more noticeable on 14 mm (28 mm FF equivalent). In addition, rotating the ND filter for different density did not seem to change vignating in a meaningful way.
To test vignating, I compared the K&F filter against a certain neutral density hoya filter, which I already have. They feel that accounting for the variance of measurement is almost identical:
So, viewing at broad focal lengths seems specific to a neutral density filter. It is not very strong and goes into the post if you only add additional improvement. I also shot a lot of videos with filters at a variety of focal lengths, and I did not get into any trouble with wigging with footage.
One thing that you have to keep in mind is that this filter uses two combined polarization filters to achieve variable effects. Because of this, at some broad focal lengths, you can get a little unequal viewing in your image, which looks like this:
I was curious if this asymmetry would appear in my measurement, and did it. Interestingly, I did not measure any significant disparity in 45 mm (95 mm equivalent), but measured something at 14 mm (28 mm equivalent). However, inequality was seen only when using filters at a strong density level. It was shown on this filter with 5 stops of ND filtration, but not with 2 stops. You can see the results below – Note, the red lines virtually blocks the same blue line:
It is a range of all variable neutral density filters, so it cannot be helped. This is mostly noted and correct, but once you are around 9 stops, it will be noticeable in real -world images. Thus, I would recommend keeping the filter the most at 8.5 stops. This ensures that you are not very close to the “X” effect, where the frame has significant inequality.
Here are two sample photos, which are accompanied by controlled lighting in the five-stop settings after the lens improvement, so that you can see that the five-stop settings are really less added to:
In addition, with polarization glass, you can also see a complete darkness of already polarized light, such as light coming from computer monitor. Then, this is not the fault of this filter, but a range of polarization glass. It is said, if you are moving or shooting in a place with a computer screen, there is a possibility that you will be indoors and will not require ND filter anyway.
Colored shift
Another factor in choosing the filter is the color shift. Some filters add a little color, while others are neutral. Ideally, the filter should be as close to neutral as possible. Again, I took a picture of a PDF color chart on a certain white balance on my screen, conducted an informal test with all the lights closed. The result here is:
The Hoya filter is quite neutral, but the K&F concept filter has a little warming. Setting the white balance taken from the same place in all three images, I measured the percentage improvement required for both white balance and tint:
This suggests that the K&F concept warmed the image a little (about 500k) and moved the image slightly towards the magenta end of the spectrum. Overall, the effect was slightly stronger than the Hoyya filter. It is said, after correcting all three images for white balance, it was very difficult to tell the difference between images, and the shift in behavior is quite minor. After improvement here all three images are waves, showing very few signs of permanent damage from color shifts:
Overall impression
Practically, I think the end of concept nano-X variable ND filter is an excellent filter. In the shooting of several hours of videos with it, I ran into some real problems. True, it shifts a small amount of color, but it is easily cured. In addition, it is not easy to find an ND filter on the market that has such a wide range of 1-9 stops. Those who are present have either a narrow range of stops or they are more expensive, sometimes important. (K & F filter is $ 73 in 58 mm size that I tested.)
So, who is for this filter? If you are a photographer who requires a wide range of ND stops, or a person who shoots a lot of videos, I think this filter will be very good. For my knowledge, it is the most practical and cheap filter with good performance. It is true that fixed filters have some advantages, but they are often impractical for video shooters. Even if you shoot only the still, they take more time to use.
If you are interested in buying this filter, see B&H or Amazon link here. Buying a gear using our link helps you support such reviews at no extra cost for you!
(Don’t forget to choose the right filter size.)
