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.

Purchased this filter to use my 70-200 lens and I could not be happier! The darkness adjustment is great, you just look through the finder and rotate the filter until you get the exposure level you want. As a test I took pictures of a lit lightbulb straight on and I got a clear view of the bulb and the lit wall around it, incredible. This will really help bring interesting new abilities to my shooting and I can’t wait to try it out in other situations.

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.

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

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

Out of the box this filter is well made, threads on and adjusts smoothly. The optics are quality and I was pleased with the photos. I did experience some vignetting when pushed to the limits, but that might have been caused with me having the UV filter still attached and like I said that was at the very extreme end of the filter position. Very impressed with the filter and it's quality. The photos were F8, ISO 100 and 1/160,1/25 and 1.6 sec. Would buy again.

So I am a big fan of most K&F Filters and this filter is no exception. It worked great on my recent trip to San Deigo for vacation. The only reason I would not give this a 5-Stars is found when the filter is attached to my lens the lens cap keeps falling off.

You probably know the brand if you are shopping for this. They are 80-90% as good as B+W for half the price. Very happy with this filter and will continue to use K&F products!

K&F is a relatively new brand to me, but they have yet to disappoint. Their products are great quality, and are competitively priced. The VND filter and CPL filters both work well on their own, or stacked with eachother. The fit and finish is spot on, and feels like quality. Depending on what version of their products you get, you’ll either get anodized black or a copper/ orange color. They seem to protect the main lens glass well, and don’t budge at all once snugged down. Highly recommend their products!

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.