Is this moiré?

[greg_janee]

<p>Is the weird coloring on the fencepost in this picture an example of moiré? I've seen moiré before, on fabrics for example, but never on this kind of surface or producing this coloration effect. And whatever it is, how can I get rid of it, or better yet, avoid it in the future? Thank you.<br>

(In case it matters: Nikon D40, 1/320 s @ f/9, ISO 200, -0.3 EV, 18-200mm @ 28mm, RAW file).</p><div></div>

[plavchak]

<p>I would say so. You can change distance to get rid of moire as one way. You can google moire and find lots of ways to avoid it. Not sure how to fix this one and still keep the wood grain detail. Maybe make it a B&W "fine art"?? I'm sure someone will have a fix for you.</p>

[peterbcarter]

<p>It's Art!</p>

[andrew_borowiec]

<p>Patrick Lavoie posted an excellent technique for getting rid of color moiré several years ago which I quote below. I use this all the time, it works flawlessly 90% of the time.</p>

 

<p>color moire is easy to get rid off;<br>

1_double the background<br>

2_apply a strong gaussian blur to it<br>

3_change the blending mode of this layer to color<br>

4_put a mask on it and remove with a brush where you want the effect of the color moire remove.. work everytime on anything any color.</p>

 

<p><a name="00W8rQ"></a></p>

[patricklavoie]

<p>thanks Andrew, you save me some searching in PN for this ; )</p>

<p>here's the result.</p><div></div>

[wogears]

<p>What a great song lead!</p>

<p><music up></p>

<p>"When- you-<br>

Scan a halftone and results make you groan,<br>

It's a moiré<br>

When you fail to descreen from a slick magazine,<br>

It's a mess...<br>

...Scusez-moi, pardon me<br>

but in most DTP<br>

that's a moiré!"</p>

[Charles_Webster]

<p>@Les<br>

Groan</p>

<p><Chas></p>

[tom_mann1]

<p>Fortunately, it's color moire, not luminosity moire. The former is a lot easier to fix (as you have seen). </p>

<p>There have been several nice threads on moire, here on photo.net. Take a look at:<br>

http://www.photo.net/digital-darkroom-forum/00W8gC<br>

Start at about half-way through the thread. That's when it got interesting.</p>

<p>Tom M</p>

<p>@Les - Another groan, but with a smile on my face. :-)</p>

[ethervizion]

<p>This is actually Moiré, plus the effect of the Bayer pattern colour filter used in the sensor, plus the raw processor (demosaicing algorithm). A raw image only has one colour component (R, G, or B) per pixel location and the raw processor (in camera or on computer) interpolates (demosaics) the remaining colour components. When you have a high frequency pattern like that, the interpolation produces false colours due to being forced to use non-similar pixels as input from the surrounding region. However, some demosaicing algorithms are better than others in mitigating this effect (as well as appropriate choice of additional processing components and parameters, such as sharpening). I'm wondering what raw processor you used and if you tried others? While it seems that Patrick has been able to mitigate the effect using post-processing, it would be interesting if you can reduce or remove it from the beginning using an appropriate raw processor.</p>

[tom_mann1]

<p>Karl, thanks for explaining the mechanism of what is commonly called "color Moire". Most folks have absolutely no idea about aliasing in the spatial frequency domain in B&W, let alone when color demosaicing gets involved.</p>

<p>Tom M</p>

[pbarnes]

Les, no groan from me, I have been singing your song all day, love it (ok, my wife is groaning, but she always does

that when I sing.)

[greg_janee]

<p>Thanks for all the helpful explanation and tips. That Photoshop technique really works!</p>