Color Casts, Vignetting, and Sharpness: Which Neutral Density Filter Is Best?

Neutral density filters seem to be all the rage these days. If you are a landscape photographer, ND filters are a crucial tool for smoothing out rough water and giving your skies a nice blurred effect. For portrait photographers, neutral density filters are great for maintaining wide open apertures in super bright situations while using strobes. Recently, we tested five different brands' filters to see which one produced the sharpest and most accurate color renditions. The results were pretty shocking.

As the owner of Fstoppers, I personally get tons of emails and messages from all sorts of manufacturers, distributors, crowd funders, and startups claiming that their particular product is better than the competition. Since Fstoppers is not sponsored by any camera company, we are in a unique situation in which we can pretty much review any series of products and pit them against each other in an all out "winner takes all" competition. Some of our reviews are pretty subjective, based on our own desires and applications (take our Sony vs. Nikon vs. Canon high-megapixel camera shootout video, for example), while others are much more objective in nature. In today's neutral density filter review, we find ourselves in the latter category.

If you have ever been in the market for a neutral density filter, you have probably read or heard that "this brand" has the most color-neutral filter, or that this company produces the absolute sharpest filter glass with a highly sophisticated xenon astrospace coating that makes your images suddenly come to life. As a photographer who values capturing the highest quality imagery, I can understand how one might buy into this hype and shell out a couple extra dollars to buy the best of the best. But most photographers simply read the reviews and make the plunge once or twice, hoping that they have made the correct decision. Recently, I was able to test five of the most popular neutral density filters side by side and see for myself how different ND filters affect the overall image quality of my photographs. 

The Setup

As I explain in the full video above, I wanted to approach this test a bit differently than what I've seen on other websites. Instead of opting to take these filters out into the "real world" and photograph a beautiful landscape, I wanted to run my test in the studio and reduce as many variables as possible. Since I use neutral density filters much more often for portraits than landscapes, this seemed not only like a great variation on a common test, but one that would produce the most compelling results as well.

In order to reduce any outside variables that might be caused by our atmosphere and changes in weather, our staff set up a simple experiment station in our studio. We used one Nikon D750 camera outfitted with a Tamron 24-70mm f/2.8 lens (our favorite all-around lens for both video and stills) so that every filter would be shot on the exact same camera and lens system. This lens was set to shoot at the widest setting (24mm), and we set our aperture at f/8.0, which would reproduce a common setup any landscape photographer might choose. We then used a single Profoto D1 studio flash firing at a white cyclorama wall to emulate our constant sunlight. We kept this light hard-edged so that no light modifier fabric would add any color to our tests. 

The Filters

For this test, I decided to use neutral density filters with six stops of light-blocking material. Having six stops of light reduction is pretty heavy for any serious studio work, but as I found working with Elia Locardi for his Photographing the World landscape series, six stops is a very common filter density for many landscape photographers. Elia actually includes a 1.2 and 3.0 ND filter in his signature Formatt Hitech Kit, which correspond to four stops and ten stops respectively. So, for this test, I wanted to split the difference and use a six-stop filter since it would cover most of the exposure times desired by landscape photographers. With a six-stop ND, you can take a relatively short shutter exposure of say 1/4th of a second, all the way to 16 full seconds. 

For the actual brands we tested, I wanted to include some of the most respected filter manufacturers, as well as a wide range of prices. Here are the actual filters we used; I've linked to them on B&H so you can see the overall reviews and prices.  

Hoya 82mm ProND64 Filter: $86

Tiffen 82mm Neutral Density 1.8 Filter: $139

Formatt Hitech 82mm HD ND 1.8 Filter: $101

B+W 82mm 1.8 ND MRC 106M Filter: $286

Breakthrough Photography 82mm x3 Solid Neutral Density 1.8 Filter: $179

Keep in mind that all of these filters are the 82mm threaded type so that they would fit perfectly on our Tamron lens. Many landscape photographers, like Elia, prefer square filters and a filter holder instead of the ones that thread directly onto the lens. I did not test these square filters, but I do think they might have significantly less vignetting because of their overall design. Keep that in mind when reading this review and ultimately choosing which filter system to buy.

The Tests

In order to see which filters were the absolute best bang for the buck, I had to come up with a few tests. The main things I wanted to compare between the five brands were color consistency, overall sharpness, and the amount of vignetting each filter might add to our photograph. Upon running these three tests, I soon realized that not every filter produced the exact same exposure, so I added an exposure test that compared the overall darkening effect caused by adding the filter to the lens. It was clear not every filter was actually cutting light by a full and constant six stops. By using Lightroom's histogram, I was able to match the overall exposure from each filter to an unfiltered control image to see how much neutral density power was being applied to each of our images.

Another thing I wanted to see was how easily I could remove any color casts that were introduced by any given filter. For this test, I used Lightroom's custom WB dropper tool on a specific area of the Fstoppers Flash Disc gray card. This allowed me to average out any change in color caused by the filter and, in theory, get five images with the exact same white balance as our control image, which did not contain a ND filter.  

The Results

If all you are really interested in which filter performed the best, then this is the section to read. In a nutshell, each filter did display some sort of color cast when compared to the unfiltered control image, and every filter did display some level of vignetting. So, on one hand, none of these filters really passed with flying colors when you compare the images straight out of the camera. On the other hand, though, almost all of these filters were pretty acceptable when the raw files were processed and corrected for both color casts and slight exposure differences.  

Color Cast: The animated GIF image below shows how all of the filters compared with the unfiltered control image. As you can see, every filter added some bit of color cast to the image. The most extreme results were produced by the Tiffen and Formatt Hitech filters, while the Breakthrough and Hoya showed the smallest amount of color shift. For me, the Breakthrough looks the closest in color to the control, even though it is slightly cooler in color than the control. 

Vignetting: The following GIF image shows the differences in vignetting between each filter manufacturer. For this animation, I switched the files around so that they show the least amount of vignetting first and end with the filters having the strongest vignetting effect. As you can see, the Breakthrough and Hoya filters have the least amount of vignetting around the edges, while the B+W and Formatt Hitech have some of the strongest shading around the outermost part of the image. I will note that the decrease in quality required by turning this comparison into a gif does make the results a little hard to see because of the banding artifacts created in the GIF file itself, but you can still clearly see how much variance there is among all five different filters.  

Sharpness: As I stated in the video, the sharpness test proved to be very difficult in determining a winner. I found myself splitting hairs trying to create an order of sharpest to softest, but I did find the Tiffen and Breakthrough filters to be the sharpest, while of course the control image had the absolute sharpest detail, which was to be expected. Overall, I would say from our tests that no one should really use sharpness as a criteria when choosing a neutral density filter if they are deciding between one of the five filters we tested. Perhaps some of the cheaper budget filters could be softer than any of these, but all five of these particular filters came out with great scores in the sharpness category. I did not include a GIF for this test because the results were so similar and the loss in quality from the gif file would not be useful in making any sort of conclusion.

Exposure: As I mentioned above, I did not set out to compare the differences in exposure because I guess it slipped my mind that exposure would vary from filter to filter. After taking each test image from the five filters, I did notice a slight variance of less than one stop between all five shots. Using the histogram feature in Lightroom, I was able to adjust the exposure to get all the images to fall on the same exposure range. In doing so, I found that the filter with the greatest difference in exposure was the Tiffen filter, which showed 3/4 of a stop more density than advertised. The Breakthrough and Formatt Hitech filters were almost exactly six stops in density, so they won this test if exposure is super important to you. Keep in mind that for many photographers, extra density is actually preferred because it gives you even longer exposure times. So, while I'm not sure this is really a negative result, the density on each of these filters was slightly different.  

My Conclusion

I must say, this was a really fun test to run, and I hope you guys enjoyed a studio test of these filters as an alternative to something out on location. From the different tests I ran, it was pretty clear that the Breakthrough Nanotech Filter was the overall winner. It is worth noting that this filter is the second most expensive filter of the group, which still leaves us with the question: "are more expensive filters worth their higher price tag?" In this case, I'm still not sure. All of the filters balanced out pretty well when set to a custom white balance based off a gray card, and I'm sure you could easily remove most or all of the vignetting shown throughout this test. However, if you want the best results straight out of the camera that do not require any post-processing, then the Breakthrough filter really shines, despite being a little more pricey than the other brands. 

On the other end of the spectrum, the Formatt Hitech filter we tested did have some of the worst color-casting and vignetting from the group, so I would tend to say it was the worst performer. As stated above with the winning filter, I have no doubt that the overall color cast can be easily fixed in any raw editor, and the vignetting may or may not be an effect that you like in your photography (I kind of do like it for certain applications). It's also worth noting that the Formatt filter was just over $100, making it the second least expensive filter of the bunch. Fstoppers personally owns a few Formatt Hitech 100mm Filters that we picked up while filming Elia Locardi's Landscape and Cityscape tutorials last year, and I have really enjoyed using them. These filters are the more expensive Firecrest Series, which claim to have newer technology in them than the standard filter we tested. To be honest with myself, I would never have really noticed the findings we found in this review out in the real world unless we put all these filters side by side. So, even though my results showed the Formatt Hitech filter to be the clear loser, I have no doubt that you can still produce amazing imagery with it even though you may have to make a few adjustments in Lightroom or Photoshop to mitigate the color shift and vignetting.  

I hope this test helps you pick out the right neutral density filter for your own photography. As we always say, great photography usually has little to do with the actual gear and more to do with the photographer, the planning, the concept, the execution, and the post-processing. So, don't get too bent out of shape over this stuff, and spend more time learning, practicing, and exploring your craft and less time searching for the unobtainable "perfect gear." 

Since I referenced Elia Locardi a lot in this article, and I have personally learned more from him about landscape photography than anyone else, I would urge you to check out the promo video we made for his full 12-hour landscape photography workshop, Photographing the World. He covers everything: scouting, composing, using ND filters, choosing the right lenses, picking the right time of day to shoot, and everything in-between. Elia's post-processing is absolutely eye-opening not just for landscape photography, but also any genre of photography where you need to expand the detail and clarity of an image. He goes through all of his Lightroom and Photoshop tricks and I am more proud of this video series than anything else I have ever helped create. We also released a much more intense and advanced tutorial, Photographing the World: Cityscapes, if that interests you more than vacant landscapes. Enjoy!