In the world of super high density neutral density filters, the options are few and far between, and the picking are largely slim due to supply and demand. The premier solution for those looking for a 10-stop ND filter seems to Lee’s Big Stopper. The only problem, demand has outstripped supply such that it’s almost impossible to get one.

Enter Formatt and their Hitech line of Pro Stop high-density ND filters. Formatt isn’t new to the filter game, for at least 3 decades if not more. However, unlike virtually every other filter maker, they recognized the demand for high-density ND filters and reformulated their line to capitalize on the demand.

While this isn’t a comparison between Formatt’s offering and Lee’s, it’s almost impossible not to draw some comparisons between them.

The Hitech filter is made from dyed optical resin with a foam gasket attached to one side in an effort to reduce light leaks. Hitech produces the filter in 2 sizes (85mm and 100mm) and 5 densities (6, 7, 8, 9, and 10 stops).

As far as ruggedness goes, I’ve found the resin filter is hands down a winner. I’ve dropped my 10-stop Pro Stop filter several times from 3 to 4 feet to solid surfaces (like concrete) without any damage or breakage. This is something I wouldn’t expect a glass filter to survive so this gets points from me.

On the other hand, the utility of the light leak reducing gasket is more debatable and will depend on what kind of holder you actually use. Personally, I use a Cokin Z-pro holder for my 4″ filters and with that holder the gasket is more or less useless in it’s intended purpose—the best light seal is when the filter is flat against the holder.

Additionally the filters come with a padded pouch/holder to keep them from being damaged when being transported.

While physically the Hitech Pro Stop is a quite solid filter, optically the story is a bit different.

First the good; my filter is, as far as I can tell, optically flat. At least I can’t find any noticeable distortion in the images that I’ve produced with it. That is there aren’t noticeable distortions of details.

The real problem is color. All high density ND filters are going to induce some kind of color shift, there is no dye or substrate that will have a perfectly uniform attenuation pattern across all colors. Unfortunately it doesn’t seem that Formatt was even trying to maintain neutrality. The following is from Formatt/Hitech’s Pro Stop Guide.

The filter has been purposely been designed to give a slight blue colour cast, to assist in enhancing landscape shots particularly in relation to water and skies.

When I did my initial research, I found a couple of reviews that showed similar degrees of colorcast between the Hitech filter and the Lee Big Stopper, such as this one. Yes, there are differences, but that’s to be expected from different filters, but ultimately to me the colors looked to be in at least the same ballpark. As I was in the process of writing this J. Holko posted his comparison between the Hitech and Lee filters, which added a data point I didn’t previously have, the color temp the camera came to using its Auto White Balance.

So where does my Pro Stop stack up color wise?

To say it has a slight blue cast would be a considerable understatement, in my opinion.

• Exposure without filter
• Uncorrected Exposure with filter
• Corrected ND Exposure

Uncorrected my 10-stop Pro Stop maxes out my camera’s AWB capabilities at its highest color temps and magenta tints. Correcting the white balance in post processing for example, often requires an impressive 13250K temperature and +144 points towards magenta for a scene that without the filter is a mere 5400K and +12 towards magenta. To correct that “in camera” with another filter would require a +110 mired warming filter (like a Lee 85 standard) and then some considerable amount of magenta to counter the green cast (or perhaps something like a Lee FL5700-B fluorescent correction filter would work for both counts).

Now while Formatt claims this aids in enhancing landscapes, it also turns what is being sold as a neutral density filter into something considerably less neutral. Moreover, while it may help a B&W photographer, it severely limits the utility of the filter for a color shooter. The colorcast ultimately means that your digital camera is collecting considerably less information in the red channels, which ultimately means that there’s considerably less room to manipulate colors and saturations and retain accurate colors.

The situation is worse if you’re stacking multiple Pro Stop filters to get extremely long exposers. There’s a real possibility of running into a uncorrectable situation where simply isn’t enough data in the red channel to recover the scene to a correct white balance.

All told, the Hitech Pro Stop 10-stop ND filter is, in my opinion, is a wonderful product built to a flawed design. It’s certainly more rugged than I think a glass filter would be, and that’s something of value to me. Moreover, I can’t say I’ve had a real problem with the images I get from using the filter, at least after they’ve been color corrected. However, designing a ND filter to deliberately not be neutral seems to be well, the wrong way to do things.