My wife and I are picked up a couple electric scooters and I thought it would be good to mount our GoPro and get some video, so filters are very nice accessory that can make a big difference. This filter is just amazing well made, such high quality and beyond. Perfect all the way around. Screws on to my camera enclosure perfectly. Filter adjusts very smoothly and it's surprising how wide a range it has. i am no photography expert, so sure it will take me some practice to get it down.

Filter comes in a nice plastic case to protect it. I only wish it came with some kind of lens cover to protect the lens when it's out of the case. I can just take it off each time, but would be nice to leave it on.

Very nice filter, price is good, gladly recommend.

K&F has been around for some time and they're a great go-to choice for value to performance. This review is for their variable ND3-ND1000 filter (1.5-10 stops). K&F does make more premium filters than this particular one, so this filter isn't their best, but it's still good. Build quality is fantastic. The inner stationary filter has two areas of knurling while the outer rotational filter is smooth. On the edges, you'll see lasered markings indicating minimum, boxes for stops, maximum, and an arrow indicating where you're at. Though this is somewhat useful, the filter doesn't always index on my lens so that is easily shows these markings. Furthermore, there aren't hard stops for the outer filter, so you can rotate it continuously. As you rotate through the full 360 degrees, you'll go through 2 full rotations of the minimum to maximum variable effect. Optical quality is on par with most of their other filters. Since you can rotate all the way through, and because this variable goes up to 10 stops, you'll run into the X effect towards the deeper end. When I tested my 77mm filter on my 24-70, it wasn't immediately obvious on the camera screen but became more apparent once I imported the photo. The filter does live up to its density claims though as I was able to achieve up to 10 stops of change. Overall, the variable ND3-ND1000 filter (1.5-10 stops) by K&F is a fantastic buy below $60 and provides great value for its performance. I've long eyed the variables by Tiffen and B+W and PolarPro but at 2x-5x the price, I couldn't justify it without even knowing if I truly needed a variable ND. If you're just getting into using ND filters and you want to play around with an entry-level cost variable that will last you a while, I strongly recommend the K&F. It runs into the same X issue found in nearly all variables without hard stops.

Exceptional value for money. The product corresponds to the description and the shipping was very fast. Difficult to find similar items in the market. The workmanship is excellent and I am satisfied with the purchase made.

If you want to achieve clean ND1000 and want to take long exposures from 30 seconds on a bright sunny day, you should buy a fixed ND filter. That part manages 400 to 500 ND at most. But very good when filming in order to be able to darken quickly and comfortably infinitely without having to change other used quality settings, I bought the ND filter for that and am satisfied with it in this area. Sharpness and colors become useless from a focal length of 200mm (I have a 400mm telephoto lens) Price/performance ok

I needed it for daytime video recordings to maintain the fps to shutter speed ratio possibly corresponding to the 1a2 ratio. I confirm that with 16/18 mm wide angles (equivalent 24/27mm full format) I can use the filter up to 2/3 of the reduction field then a vignetting or the X effect is generated. If we go to 35/50 mm at Massimo I see a not heavy vignetting. I recommend it for non-professional use and for the convenience of being able to carry it in your bag without much clutter (as an alternative to non-ND filters or 100x100). Light dominant. For my use (640iso -flog and f4-5.6 aperture with focal length > 23mm in sunlight) it is more than enough.

This is a filter feature I have wanted for a long time but always considered a multiple filter set, not a single variable filter. To my satisfaction I found this single variable filter works very well and takes up minimum space in my camera bag. The effect given by this filter is also such that I don't have to worry about losing sharpness due to an inferior piece of glass. I use it primarily on my Canon EOS M50.

One of the better variable ND filters I've used. The build is extremely good for the price. I really like that it is a slim build and doesn't make your setup overly clunky.

He does his. It is not a top of the range but the value for money is excellent. The only flaw, if you increase by too many stops you can see the so-called x effect, but you don't have to go to many stops to get amazing shots. Great for those who, like me, try their hand at these types of filters for the first time

I'm becoming a fan of K&F Concept filters. This is my third filter from them and so far I've been extremely impressed with the glass.

CONSTRUCTION
The filter attaches to my lens smoothly and comes off without binding. The frame is machined very well with a semi-rough coating that makes for a secure and confident grip on the filter while adjusting it. Adjustment is very smooth with quite a bit of resistance and won't change if you happen to brush up against it. You can gauge the VND effect with markings on the edge that range from "MIN" to "MAX" with a series of square dots that gradually increase in height.

VND filters tend to be thicker and can cause vignetting with shorter focal lengths. K&F's solution to this is to make the filter slightly larger than the lens diameter (about 71mm on the 67mm filter I'm reviewing). This works great to prevent vignetting but it means that you can't use your existing lens cap. Using a lens hood is theoretically possible but the larger size means it'll be very difficult to set up even if it fits.

I have another K&F filter set that came with really nice machined caps. With the larger front ring diameter that doesn't fit your lens cap that would have been a great add.

TESTING

This filter is specified to produce 1.5 to 10 stops of light reduction. I measured approximately 1 1/3 to 12 stops of light reduction with no visual artifacts such as the dreaded "X" effect you get with some VND filters. The filter imparted a slight warm cast (~300K) that remained consistent throughout the range getting slightly warmer only at maximum.

K&F state that the filter markings are not calibrated. I measured the effect under relatively controlled conditions and found that the VND effect isn't linear but instead starts off slowly but increases much faster as you approach max. Because of this adjustments at higher strengths can be quite tricky.

I would have really appreciated calibrated markings to make adjustment easier, but since it doesn't have this feature I measured the approximate strength and made a chart.

MIN
Solid 1-4 = 1 1/3, 5-6 = 1 2/3, 7-8 = 2, 9-10 = 3, 11 = 4
Hollow 1 = 5, 2 = 7, 3 = 12
MAX

You can ignore the Min and Max markings since they don't produce any meaningful changes.

SUMMARY

With this filter you're getting great neutral glass that's comparable to much higher-end products at a much lower price point. Even with minor negatives it's a fantastic all around value. Highly recommended.

PROS
Minimal color cast (+300K)
Adjustable from ND3 to ND1000 (1.5 to 10 stops)
Multilayer coatings for glare reduction, resistance to skin oils and easy cleaning
Does not vignette
Graduated markings from 'min to max'
Threaded front ring

CONS
Filter is larger than the lens diameter
You can't use your lens cap or lens hood
Markings are not calibrated
VND effect is decidedly non-linear and tricky to adjust at higher strengths

If you are new to photography, this is a good filter to start with