Nikon creates selectable strength low-pass filter

Dec 3, 2012
N Idaho

(some diagrams/pictures at the URL)

Nikon has patented a technology that can electronically adjust a camera's low-pass (AA) filter based on the situation. By using a liquid crystal panel, the AA filter can either be turned on and off, or set to 'normal' or 'high' intensity. The first design could allow for a digital SLR to have its AA filter turned off at the press of the button. The second design would have a mild anti-aliasing effect for stills, and a stronger effect to eliminate moiré in movies. The company suggests still more could be achieved by mounting two such filters back-to-back.

The patent claims the entirely electronic design means a two-mode low-pass filter can be implemented in a way that doesn't decrease the reliability or durability of the camera (rather than a mechanical system that switched different filters into place).

How it works:

The designs are essentially a development of the filters used in the D800 and D800E. The standard D800 has a low-pass filter that utilizes a property called birefringence - where a substance splits light depending on the light's polarization. The thickness of the filter
defines how much the light is split, so the thickness of the filter can be tuned to match the sensor it's placed in front of (Blurring the light across the width of one pixel cuts out the high frequencies that would cause moiré).

The D800E features a second birefringent plate of the same thickness, set so that it re-combines the light split by the first plate - cancelling the effect.
The Nikon patent inserts a liquid crystal layer between the two plates. A liquid crystal layer can be made to rotate the polarization of light or just let it pass straight through, depending on whether an electrical charge is applied to the layer. This ability to change the polarization of the light as it passes between two polarization-sensitive plates lets you decide whether the effects of the two plates is additive or subtractive.

In the simplest system described in the patent, the first layer separates the light before it hits the liquid crystal. With the liquid crystal turned off, the polarization of this split light is rotated through 90 degrees, causing the light to be recombined by a second birefringent plate. However, if the liquid crystal is turned on, it doesn't rotate the light, and the second filter exaggerates the splitting effect and increases the blur.

The result is a low-pass filter with two modes. In one instance you could have a filter that can either be turned on or off (offering a high-res mode if you're shooting landscapes or situations without repetitive patterns).
Dec 26, 2010
Pretty cool technology!!!

Would I want one in my DSLR? I'm not really sure. I don't think it would benefit most people and add another variable and level of complexity into an over complicated piece of electronic gear. I like to have full control over all variables in my gear, but never really found the AA in the D800 or any other camera to be a roadblock for me. I guess if Nikon put in a selector switch I would have to play with it to really see a side-by-side comparison to be sure.
Apr 15, 2008
Miami, FL
While this is technically interesting, I think it will have limited appeal at this point in time. Until the photographic zeitgeist embraces the concept of reducing/removing the AA filter to increase sharpness, this will remain a niche feature for landscape photographers and really picky portrait pros (please forgive the alliteration). That being said, I just put a deposit down on a D800e.
Jun 3, 2009
Chicago "burbs"
So far, every image from my D7100 (no AA filter) has been stunning. I feel that the AA filter is less necessary than necessary (imho). Instead of Nikon spending R&D into this new "feature", why don't they address the left af issue with an already existing product?? I know a company has to develop new features for the future, but what about the past issues that were never formally acknowledged?
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