Points in Focus Photography

ND Filters, Marketing, Specifications, and Agrivation

Christmas brought me a Lee Big Stopper, and I’ve been working writing a review of it as well as testing it out to figure out how I can best put it to use. I already had a 10-stop ND filter, a HiTech Pro Stop, but the color casts it imparts render it almost impossible to shoot color images with it. My research pointed me to the almost impossible to get Lee Big Stopper as being a solution to that problem.

This isn’t a review of the Big Stopper, in fact, what I want to talk about here isn’t the performance of these filters, but the near complete inability to talk, market, or describe them in what I would consider a useful manner.

The simple reality is, I’ve yet to meet a 10-stop ND filter that actually is neutral. Whether by design or as a side effect of the construction process, there appears to be ready way around a color cast. However, the marketing and technical specifications for the products should be much more clear and up front about this, and about how much should be expected than they actually are.

To give credit where it’s due, both Lee and HiTech do note the issue in their documentation. How well, perhaps is more of a matter of debate.

Though both Lee and HiTech do warm of color casts, they do so with perhaps the last useful language possible. Lee says, “Use of the Big Stopper may result in a slight colour cast,” likewise, HiTech says, “The filter has been purposely been designed to give a slight blue colour cast.”

What exactly is a slight color cast?

Merriam-Webster says the word slight mean a “small of its kind or in amount <a slight chance> <a slight odor of gas>”. So with that working definition the color cast shouldn’t be that big of an issue should it? Does the image below show a slight color cast? Does it help when I note that it was shot under 2800K tungsten lamps?

5650K, +59 magenta, 0Ev, 240s, f/5, ISO 400

Personally, I have a hard time describing that as slight, yet that’s the that’s the slight color cast my HiTech ProStop produces. It’s green, in fact it takes almost 130 points of magenta tint and nearly 130 mireds of blue to render the color balance in that image correct. The slight cast from that filter is so strong, that under bluer conditions, such as daylight color temperatures, it becomes very difficult if not impossible to correct for the color cast the filter imparts.

What I find so amusing about this is that while these high-density ND filters have their color casts described as slight, the same amount of color change in a color correction filter made by the same manufacturer is described as major or significant.

My point isn’t that all of these high-density ND filters have color casts, though I’d certainly prefer it not to be there to start with. The problem I have is that the manufactures seem so adverse to actually putting the information out there for photographers to work with to begin with. I don’t really think either Lee or Hitech go far enough in this regard. I’d love to see two things from every manufacturer making a high-density ND filter.

First, I think manufactures should publish the tolerance ranges for both color shift and density on their product pages. I shouldn’t have to guess, dig though tons of pages, read a half dozed FAQs, and watch a YouTube video to get the complete picture of how the filter should perform. Nor should I have to contact support to determine if my filter is performing properly when some reviewers get shifts less than half of what I’m seeing and others don’t. I should, however, be able to look at a spec sheet on the product page and see that the filters are designed to be 10 stops plus-or-minus 2/3rds of a stop, and have a 30 mired plus-or-minus 10 mired blue color shift.

Secondly, I’d love to see them include a calibration card that listed the density and color response of that specific filter. Since ever filter is going to be slightly different, this goes a long way towards flattening the experimentation curve and eliminating errors. If the filter was tested to be 10-1/3 stops, I can adjust to that instead of having to guess and make notes and hope I didn’t mess up my tests. The same can be said for knowing the color shift I should expect as well. My testing of my Big Stopper has resulted in numbers all over the place, from 131 mrds to 70 mrds depending on factors I’m not even entirely clear on (and even under repeated tests under the same conditions).

The manufactures have the hardware to do this far more precisely than I can with my camera and it would go a long way towards saving me the hassle of spending time trying to work it out myself. Of course what would be even better would be to actually make the filters neutral in the first place but I’m guessing that won’t happen.

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