I recently discovered these ND filters while in Japan. I had never heard of True ND before and you probably haven't either. There claim was that unlike other ND filters their filters produce no colour shift and have no IR pollution. They are marketed as having true neutrality. This is a pretty big claim and I was eager to test them out for myself.
I conducted a variety of tests and put the True ND filters up against the ND filters I had from Tiffen and Redrock Micro. This test is as technical as I can make it given the equipment I had to work with. My base was always the Sony F55 with clear ND balanced with a 18% grey card. This way I had a reference for colour shift. By adding ND after balancing the camera I could see if there was any colour shift.
Like most people I have never really taken the time to look into how ND changes colour shift. The results were quite surprising. While a lot of modern day cameras have built in ND and IR protection even those can produce colour shift to a certain degree.
There is of course a strong argument that you could just re white balance every time you ad ND. Well yes you could......but your changing the colour temperature of your entire scene. I would prefer neutrality when using ND because I want to have a consistent colour temperature and look whether i'm running no ND or running ND.
Now this isn't a blanket ND filter test as i'm only comparing 3 different filter manufacturers. I can only show you differences between the True ND, Tiffen and Redrock Micro. All 3 brands are of varying quality and price.
I will leave you to judge the results of the tests yourselves. I can only offer a personal opinion of what my conclusions were. For me the True ND was by far the most neutral of the 3, It wasn't even really close. They do retail for $600 each so they are not cheap. So did they live up to their claims of true neutrality? Well i'm not sure if that is the real world case, but they are super close. I was very impressed by the results and I don't say that lightly. One of the other things that surprised me was just how consistent the True ND filters were at high levels of ND (0.9, 1.2, 1.5). The Tiffens started to suffer from bad colour shift once you got over 0.6. To my eye the True ND 0.9 actually out performed the built in 0.9 ND on the Sony F55.
There was no colour correction or sharpening done to any of the footage.
I am not the only one to come this conclusion. You can check out this test by Ryan Walters here: ryanewalters.com/Blog/blog.php?id=6201317295579746489
For more information on True ND filters you can go to: