ND Filters' Color Cast comparison - Vü 10 stop Sion, Lee 10 stop (Big Stopper) & Formatt Hitech 8 stop
The Lee Big Stopper was introduced in 2010 to compete with the Hitech 10 stop filter that was known to have flare and other issues. Subsequently Hitech reengineered their 10 stop filter and emulated some of Lee’s design features. In particular the the light blocking gasket. Soon Lee introduced the Little Stopper while Hitech developed a wider range of solid ND filters the Pro Stop line from 6 to 10 stops and in multiple sizes. Most recently I was introduced to the Vü system and hence this test as a comparison. I will do a full review of the Vü system in the near future.As I own the Lee Big sStopper and the Hitech 8 stop with the Hitech holder (I do prefer the Hitech to the Lee holder) I was keen to understand the differences in the way high f-stop ND filters impart a color cast when used. Hence this test. Please click on the images to see a larger version.The set up was fairly simple. Using a Sony A7R II and a Zeiss Batis 85mm f/1.8 lens set at f/2.0 and a base ISO of 50, shutter speed 1/125 sec. The light source was two Elinchrome studio strobes positioned to give a 1/3 stop exposure variation at the edges. The camera was focused on a white foam-core board with a X-Rite Color Checker Passport clamped to the upper right corner. Camera white balance set for flash rather than a custom white balance (5450 Kelvin) and an "as shot" tint of +9. I wanted to allow for any variation in the white of the foam-core board that is typically not 100% white be adjusted in post.The test exposure was made and the white balance adjusted in post using Lightroom - this is the image below. White balance adjustment yielded a temperature of 4750 Kelvin and a tint of -1:
Next the strobes were adjusted to full power providing 8 additional stops of light. The ISO was adjusted to increase sensitivity by two stops while the aperture of the lens was kept at a constant f/2.0 for all the exposures. Each filter was tested for color cast only.
The Lee Big Stopper (10 stop ND)
The Lee Big Stopper (10 stop ND) was mounted and the image as shown below was captured. This is as a screen shot so as to show the RGB histogram. The info panel shows the reading from the center of the captured image. Values are R=219, G=229, B=243
In this next image the Info Panel shows RGB values from the lower third of the image. Values are R=187, G=203, B=222
Next the image was white balanced in Lightroom WB to 8600 Kelvin and tint +43. Compensated for the color of the board and the lights the calculated readings are 7900 Kelvin and a +35 Tint adjustment.
The Lee Big Stopper exhibits a heavy blue cast in both the center and the edges.
Formatt Hitech 8 stop ND filter
As I do not have a 10 stop Formatt Hitech filter, I chose to do the same test with the 8 stop that I own. As with the Lee filter before, here the info panel shows the reading from the center of the captured image. Values are R=234, G=238, B=236
In this next image the Info Panel shows RGB values from the lower third of the image. Values are R=209, G=220, B=212
Next the image was white balanced in Lightroom WB to 5750 Kelvin and tint +52. Compensated for the color of the board and the lights the calculated readings are 5050 Kelvin and a +44 Tint adjustment.
The Formatt HiTech 8 stop exhibits a heavy green cast at the edges but is more neutral in the center.
Vü Sion Q 10 stop Neutral Density Filter
The Vü Sion 10 stop ND filter mounted using The Vü professional filter holder (more abut this in a future post) and the same test was performed. As before the image captured is shown as a screen shot showing the RGB histogram. The info panel shows the reading from the center of the captured image. Values are R=235, G=235, B=239
In this next image the Info Panel shows RGB values from the lower third of the image. Values are R=211, G=214, B=219
Next the image was white balanced in Lightroom WB to 5800 Kelvin and tint +13. Compensated for the color of the board and the lights the calculated readings are 5000 Kelvin and a +5 Tint adjustment.
The Vü Sion 10 stop is very neutral in the center an has a negligible shift at the edges.In conclusion I am very impressed with the Vü Sion 10 stop and is near neutral rendering. My full review of this system is forthcoming.