The filter is thick but it is also larger than 67mm so the effective area is less affected by the thickness. I used Fuji 18-135mm lens to test this filter. When I set the focal length to 18mm (27mm Full frame equivalent) , I did not notice any vignette caused by this filter. Another test I did was set fixed aperture and shutter speed. Only thing that would vary was ISO. I then turned the filter to each ND level on the mark. I could clearly see the ISO keep moving up as the ND index went higher. When I compared the JPG results, I notched not much difference among those shots in term of brightness, color, or sharpness. So I would say that the filter is consistent within its intended stops. With these results, I would give this filter a go. With such a small package for 10 stops of ND, I definitely will throw it into my bag in travel.

I ordered this to use with my favorite walkabout lens, in an effort to get myself back in the habit of taking photowalks on a more regular basis. I had to stop because of my mobility issues, and it's taken me years to get back to a point where I might be able to manage a slow 20-minute walk on less-than-smooth ground, but it's time.

The filter size is accurate and it screws easily into my lens. The coatings are smooth, with no ripples, bubbles, or uneven appearance at any point in the rotation. The ring rotates easily and smoothly, and it's easy to see the glass visibly darken as it's rotated.

The photos come out crisp and clean, without the haze that's often attributable to unpolarized light, and unlike with some lower-quality ND filters, without any hint of a moiré pattern.

The filter works best if you have a lens that is greater than 35mm. When the lens is too wide angle is when you get the X looking area

I have wanted a ND filter for some time, and a variable ND is just the right thing! Using a ND filter allows you to take much longer exposures while keeping the aperture wider open particularly during daylight hours, all while maintaining a NEUTRAL color effect on the picture. I got the 77mm as that fits both my 24-70 and 70-200 lenses, and I can adapt it down to fit a couple other medium range zooms I have.

I really like that the inner ring has textured grooves which greatly simplifies tightening and removing the filter from your lens. Turning the outer ring is firm, but not overly stiff, yet tight enough to stay where you put it without easily turning.

RECOMMENDED

I have other K&F's and they all perform as advertised. This one is no different. Well made, good images, works as expected.

"Real" photographers, such as Rick Sammon can't say enough bad things about variable ND's. I have used them for years and never once was disappointed by them. The bad mouth guys are always complaining about the "X" issue. Yes, if you turn too far, you'll get an ugly X across your photo. Here's the secret which as served me well for a long, long time. You ready? "Don't turn it too far". I don't know why that is such a tough concept to master. Of course, the lazy manufacturers could help the situation by putting stops on the filters, but they seem to prefer the complaints to a simple, positive move. For my part, I help myself by gobbing on some white nail polish on the three points in question, so I can easily pick out the "too far" points. I can turn it down to focus/compose, then turn it up to where I want it and shoot. That beats the heck out of trying to shoot the image blindly, or repeatedly screwing and unscrewing the filter to get the shot arranged.

Really, a reasonable price, a little common sense, and you'll be good to go with this filter.

I hope you found this information useful and/or helpful.

I have come to rely on K&F for a number of filter types for my many lenses. They are well made with quality glass and I have yet to find any real faults or negatives in these great value filters. You would have to pay a TON more for filters that are only slightly better than these!

This variable ND3 to ND1000 filter provides highly capable ND correction from 1.5 to 10 f/stops. It is a 67 mm filter that is widely used...especially for the majority of Tamron lenses as well as a plethora of Sigma, Sony and Canons as well, which makes this filter an even better bargain.

The variable range is done simply by rotating the front dial of the filter until just the right ND level is found in the viewfinder. The filter features 24 multi-layer coatings to provide the clearest and distortion-free optics, using Japanese glass (Excellent) and precise CNC machining.

I can honestly say that this variable ND filter is almost as good as filters that cost as much as five times more. Construction is very good and the filters mount to appropriate lenses without drag, rubbing or other issues. Simple operation and fantastic results!

All in all, and especially at the value price, this set earns an easy FIVE STARS with me, and I can honestly and heartily recommend the set for your appropriate lenses.

Challenge number 1) The K&F Concept 77 mm Variable ND filters I purchased arrived later than promised and I was not able to use it for my 9 day photoshoot. Challenge number 2) It fits on my camera lens but needs time and patience to attach to the lens but it does fit. Challenge number 3) No positive stops, no detents to let you know how far you've gone (my ND filter 1.5-10 stops). In addition, if you are invested in using your lens hood while shooting, it won't fit with these ND filters.

I'll be using the ND filters on my next photoshoot and will submit an update to my review.

Spoiler Alert: My ratings mean nothing. I haven't bought this filter yet. However, I see the question in my headline both in the Questions about the product and in several users below who ding the product because it uses two polarizers or the filter doesn't work with a CPL. The answer to the question above is misleading and those reviews below aren't fair. Above, the seller says you could add a CPL filter to this VND filter, (true) but, based on what I've read, the results of doing will be very unreliable. Here's why: all VND filters work using two polarizing elements. (Don't complain when your VND has two elements.) One element is a linear polarizer and one is circular. As you turn one, the filter darkens or lightens. Now imagine stacking a CPL filter on top of a VND filter. This really creates three polarizing filters - a linear polarizer, a circular polarizer, and another circular polarizer. That's a lot of polarization for a photographer to keep track of, especially if your VND filter is dialed down so you can't clearly see the shot, which happens with ND filters. Let's pretend you wanted to shoot waterfalls with a VND filter and a CPL filter stacked on top of it. Imagine creating this shot given what I've told you. I couldn't do it reliably. (I might get lucky.) So, if I wanted to shot an image that required both a ND filter and a CPL filter, I'd probably get much better results with both a standard ND filter, which removes the polarization, and a CPL. I hope this helps potential buyers of this item. I'm asking for this filter as a birthday gift. So I'm not a buyer yet, but I hope my wife will be.

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

This is my first variable ND filter and Im very happy with it. I got the 77mm version because its a very common size and I already have three lenses that it could fit. Plus with adapters, I can get my smaller lenses to work as well.
The filter. Overall its great. Metal construction with a very smooth ring.
The stops are marked on the ring and the overall construction is very good.
Again this is my first variable ND and so far I'm enjoying it very much.
Price is affordable too.