moire


23
2015

Nikon D810 and a Taste of Moiré


Much has been said and speculated about sensor moiré in high-resolution cameras like the Nikon D800E and D810. It's an unavoidable artifact of the digital capture world, due to the interaction between finely-detailed repeating patterns in subject matter and the raster rows of modern camera sensors. It's typically an issue in architectural and fashion photography, where fabric and fine details trigger the effect.

In the endless quest for maximum resolution, Nikon has removed the anti-aliasing filter in these cameras, which helped control moiré at some loss of sharpness. Sensor moiré can't be accurately seen in preview, as the display will create its own moiré that may not actually be in the image file. And this type of moiré is different from that occurring with 4Color process images, in either scanning or prepress. So: how big a problem is it?

Here's an example of just how extreme moiré can be, in the 36 Megapixel Nikon D810. These screen grabs are a section of an image of the outdoor display panels at the beautiful new American Veterans Disabled for Life Memorial, in Washington, D.C. The site features strong horizontal black bands of varying width embedded in glass, to create tonality in the very large panels. Look what resulted once I opened up my photos on the computer:

Nikon D810 moire sample 1

Large glass panels with embedded horizontal lines create
both color and luminance moiré.

Here's a closer view from the original file. You can see the bands of color. How bad are they?

Nikon D810 moire sample 2 Nikon D810 moire sample 3

Yikes! They're that bad, and a powerful creator of eyestrain to even work with such an image!

You see the the beginning of efforts to isolate and remove the effect in Photoshop, by building paths and tight selections. Moiré is even present in the very sharp type layer. What a nightmare!

Nikon D810 moire sample 4

Low-res preview is even more horrifying!

Can such an extreme case be fixed, or even prevented? Some suggest twisting the camera at a slight angle to minimize such moiré, but that's not always practical in tight compositions and the pressure of photo assignments--especially when the effect is not visible in camera.

To repair, there's many helpful tips available online, but in the end, it's a lot of work, and a compromise between maintaining detail and residual moiré. On this set of images, many such techniques were necessary; too extensive for this blog post. I'll post some useful resources in a followup.

Here's a small piece of the near-final result. Bands of color are completely eliminated, and residual moiré (slight diagonal banding in the fabric) is not objectionable across the entire image. Note the sharp text with no moiré or signs of blurring.

Nikon D810 moire sample 5

In the days of film, there would have been no such problem, at the price of considerably less image sharpness, ease of color enhancement, and with greater detail-robbing grain. But in this case, film would have saved a huge amount of post-production time and effort.

Indeed, all that terrific sharpness and resolution we are now capable of capturing can be both a blessing and a curse....