Filters, such a useful tool for allowing more control over your exposure. Some things are simply can’t be done with a camera alone. But with so many manufactures, types, and price differences buying a filter might get a little confusing.
While it would be nearly impossible to test every filter around. I did manage to assemble a decent collection in the hope to see the differences between cheap, expensive, square, screw-in and variable NV filters.
As you can see I have a mixture of square and circle ND filters that are 10stop in strength. I also added two 6stop filters and variable ND into the mix.
Filter list
Here is the list of Square Filters, and their price today (Nov, 29th, 2020):
And the list of Screw-in filters
and finally, Variable ND filters
What type of filter you want will vary on your needs. Square filters require a filter holder to work but offer more control with stacking as well as the ability to slide graduated filters into the right position. Circular filters don’t need a filter holder but offer less control. Variable ND filters offer many stops of light control in one filter but can alter the image as you can see below.
Notice the difference in reflections here simply by rotating the whole VND filter, this isn’t something a normal ND filter will do.
The type of filter you need really depends on your preference and what you need them for. I personally like using filter holders because I hate screwing filters on and off my lens. Especially because I change a lot of filters. Some companies, like Kase, do offer a magnetic series. So as you can see, it’s a jungle.
OK, let’s dive in
The Setup
To test the filters I set up a small scene at home,. I used my Spekular LED as the main light due to its daylight balance and high CRI. This way I could keep the lighting and exposure consistent. Now any exposure or color shifts are from the filters and not the ever-changing light outside.
I also used the Sigma sdQ-H and 70-200mm f2.8 Sport at 100mm f5.6 to test the sharpness of each filter. The longer focal length along with the Foveon chip helps to stress the sharpness of the filters, particularly as the 25.6mp Foveon chip scan renders similar detail to a 50mp Bayer Chip. All images shot in JPG in-camera.
The Test
First up we have the image taken without any filter at 1/30s.
The next step was to adjust the camera exposure for each frame, for the 10stop filters I increased the exposure 10-stops to 30s and adjusted the camera for the other filters accordingly.
Before I get onto how each filter performed, I wanted to take a little time going over two that were very similar. The Kenko and Hoya filters. Both of these filters not only shared the same retail packaging but with a different insert. They are also physically identical too, with the coating on the glass being the only difference.
In testing, sharpness was the same, colorcast and brightness were different though, with the Hoya being around 1/4 of a stop darker than the Kenko. I decided to leave the Kenko filter out of the comparison image.
Color
After testing the rest of the filters I created this collage to show the full scene taken with each filter. (Click here for higher res)
Looking at the results here they are all very close. The Marumi filter seems to have the coldest color cast while the K&F NVND 8-128 has the warmest.
They all landed pretty close to their rated stops of light reduction. The B+W filter being the darkest by around a 1/4 of a stop and the Lee Pro filter is just about spot on. I made a mistake shooting the K&F VND 8-128 at 8-stops instead of 7-stops which is why that particular one is brighter
The Marumi filter here as the strongest cool color-shift while the K&F ND 8-128 variable had the strongest warm color-shift. Haida seems to be the most neutral of them all. Interstingly, the B+W seems to be actually being darker than its 10stop rating.
Using the 100% values in Lightroom I gathered the RGB data from the same location on the color checker to see the brightness/color difference in numeric value.
| R | G | B | ΔR | ΔG | ΔB | Comment | ||
|---|---|---|---|---|---|---|---|---|
| No filter | 48.3 | 49.9 | 51.3 | 0 | 0 | 0 | Benchmark | |
| Square Filters | ||||||||
| Benro Maste10-stop ND | 52.6 | 55.4 | 55.7 | 4.3 | 5.5 | 4.4 | – | |
| K&F Concept 10-stop ND | 52.6 | 53.4 | 53.9 | 4.3 | 3.5 | 2.6 | – | |
| Lee FilteProGlass 10-stop ND | 49 | 50.5 | 55.7 | 0.7 | 0.6 | 4.4 | – | |
| Haida Red Dimond 6stop ND | 47.7 | 47.9 | 49.4 | -0.6 | -2 | -1.9 | – | |
| Formatt Hitech Firecrest 6-stop ND | 49.8 | 51.5 | 55.7 | 1.5 | 1.6 | 4.4 | – | |
| Screw-in Filters | ||||||||
| B+W XS-Pro 10-stop | 42.2 | 43.4 | 46.9 | -6.1 | -6.5 | -4.4 | – | |
| Hoya PROND 10-stop | 45.9 | 47.5 | 51.5 | -2.4 | -2.4 | -0.2 | – | |
| K&F Concept 10-stop ND | 53.7 | 53.2 | 54.6 | 5.4 | 3.3 | 3.3 | – | |
| Kenko PRO ND 10-stop e | 52.7 | 53.7 | 55.1 | 4.4 | 3.8 | 3.8 | – | |
| Marumi Exus 10-stop | 52 | 53.7 | 61.3 | 3.7 | 5.2 | 10 | – | |
| Variable ND filters | ||||||||
| K&F Concept ND8-128 VND | 62 | 61.2 | 58.6 | 13.7 | +16.3 | 7.3 | shot 1 stop brighter. | |
| Haida Variable ND insert | 57.8 | 59.4 | 58.6 | 9.5 | 8.7 | 7.3 | requires m10 holder | |
Sharpness
Now that we have seen how the filters perform with light transmission and color reproduction what about sharpness? For that, I created a selection of crops (click here for higher res).
As you can see most filters had zero perceivable effect on the image Sharpness. Even using such a high resolving sensor and longer focal length. Although the Formatt Hitech Firecrest and Marumi filter did soften the image a bit.
Results
I don’t feel there’s any major advantage with color, light reduction or sharpness with most of these filters. We are getting to the point when most filters offer great quality. The deciding factors will probably shift to price and other features. That said, I do feel the Marumi 10-stop and Formatt Hitech Firecrest 6-stop where the weakest of the crop in terms of optical quality. But looking at other features, may make you shoose them nontheless.
For example, The Formatt Hitech Firecrest filter is made of two layers of 1mm glass with the ND layer in the middle. This makes it a very durable filter that would be better suited for harsh conditions where you could possibly scratch the coating on a normal glass ND filter.
Some filters have Infrared light reduction or IRND to help stop light pollution that could contaminate the image during long exposures. This also depends on how strong your IR-cut filter is on your camera but didn’t seem to be an issue on my sdQH during this test.
Lastly, some filters like the Haida Red Dimond series also use phisically stronger glass that should offer more protection if you drop the filter. Which you don’t. But if you did. Which you won’t. Anyways, filters are made of glass so its best to avoid that anyway.
Conclusion
One take away from all of this is that you can’t use price alone to gauge the image quality of a filter. The K&F 10stop ND filter being the cheapest here at $57. Offers performance that is up there with the Lee ProGlass at a whopping $237. It even comes with a nice little case with a pull cord for easy access.
Honestly, with the incredible value that K&F offers on their filters, it’s easy to recommend them, particularly to people just starting to explore the need for such things. There are other factors to consider though. Haida for example offers a wider range of filter strengths, sizes, and graduated filter types than K&F concept. do. This can be a deciding factor if you want to build a system of the same stuff.
I personally use a mixture of K&F Concept, Haida and Benro at times for my 100mm kit while using Haida rear and 150mm filters for my ultra wide.
Whatever filter system you go for these days, sharpness and color cast seems to be the last thing you need to worry about. This lets us as creators focus on ease of use, features, and such to pick what suits us best. Although it’s always best to do some extra research on a particular filter before buying.
Here are some shots showing what you get inside each filter box.
If you got a favorite, let us know in the comments!