Moiré pattern is typically created when two grids are overlaid at an angle. In video and photography, the main grid is the sensor which records the image. The second grid can be anything from fine fabric to architecture patterns. When these two grids interact at a certain angle and distance from each other they can create a moiré pattern. These patterns manifest themselves as ugly colorful waves on fine texture areas of an image. Fortunately, most camera manufactures place anti-aliasingfilters in front of digital sensors, which greatly reduces moiré occurrence. However, because these occurrences are so rare, many photographers do not even know that these annoying 'colorful waves' are called moiré. Once in a while, in specific situations, virtually any camera will inevitably create an image with moiré effect. Unfortunately, moiré pattern is not visible through the viewfinder and because of the way most resize algorithms work; you may not even notice moiré effect on the preview screens. Most of the time you will only see it on your photos when it's already too late to correct it optically. The good news is that it is possible to remove moiré in Photoshop. It is also possible to get rid of moiré pattern in other applications, such as Lightroom and Capture One 4 Pro, but for the purposes of this tutorial I will only focus on Adobe Photoshop CS6.
Mastering the moire' menace. While there are come 'cures' available in Photoshop, Lightroom offers the best solution for this unfortunate situation. Start by entering the Develop module (D.) Click the Adjustment brush or press K. Double click any slider that is not centered in the dialog to return it to the zero position.
Moiré pattern is never pretty. https://bluw.over-blog.com/2021/01/el-capitan-release-date.html. Even though it's often colorful and wavy, I always cringe when I see it pop its ugly effect on model's clothing or furniture fabrics. Although I must give credit to camera manufacturers; they do their best in implementing all kinds of tricks to minimize moiré occurrences and these tricks works 99.9% of the time. Throughout my career I have had moiré pattern on 20-50 images at most, while I have shot hundreds of thousands of images. Additionally I have only had two or three images with moiré effect on my Canon 5D Mark II. Nikon, for example, offers two versions of its D800 camera – a standard model and D800E model, which has a different low-pass filter that produces sharper images, but creates moiré effect more often. Of course there are ways to avoid moiré during image creation (some of which I will describe at the end of this tutorial), but chances are, you are reading this tutorial because you already have an image with moiré effect and the only way remove it at this point is through post-processing. There are numerous ways to actually do it, but here I will go over the quickest way I know how to remove moiré in Photoshop, that also preserves image quality.
Step One: Remove false color
Above is an image from one of my recent fashion shoots. Overall, the photo looks nice, but because of model's fine dress pattern, my distance to the subject and camera angle, moiré is all over her clothing. This is very distracting and obviously unacceptable. While it might be ok as a small thumbnail image, this file cannot go to print with such a horrid moiré pattern.
- The first thing you should do is create a selection of the entire problematic area (in this case her whole dress) using Quick Selection tool and/or Magnetic Lasso tool. If you are not fluent in object isolation in Photoshop, check out this tutorial.
- Once you are confident that the selection is precise, create a new blank layer, select a Bucket tool, hold [Alt] on Windows or [Option] on Mac and click on the color best representing general selection color. Then let go of all the keys and click on the selection to fill the new layer with that color. I'll name this layer 'Dress'.
- Then set the blending mode of that layer from Normal to Color. Check out this tutorial if you are not familiar with blending modes.
- Finally, hide this 'Dress' layer you've just created by clicking on a little eye icon next to it, we will need this layer at the end of this process.
Step Two: Remove the waves
Moire Pattern Removal
Now that we've dealt with the color, we need to eliminate the wave pattern. If you check the channels of your image, you might discover that this wavy pattern is present in all three – red, green and blue channels to some degree. Therefore, we would need to repair the Luminosity Channel to minimize the visibility if these unwanted waves.
- Make sure you load the same selection you've used for the 'Dress' layer. To do this, you have to have the 'Dress' layer selected and then go to Select>Load Selection on the top navigation bar.
- Now select the first/background layer and create a new layer above it with a blending mode set to Color. You can do this by pressing [Shift]+[Ctrl]+[N] on Windows or [Shift]+[Cmd]+[N] on Mac or going to Layer>New>Layer and select ‘Mode' to ‘Color', or just click on New Layer Icon in the Layers Panel and set Blending Mode to Color.
- Then fill this new layer with solid white color. You can do this by using a Paint Bucket tool or go to Edit>Fill ([Shift]+[F5]) and select Color to white. This will turn your selected area into Black and White. This layer is needed to be able to see the best Hue and Saturation combination at which moiré disappears.
- Now load the selection from the 'Dress' layer again. Then select the first/background layer again and create a Hue/Saturation Adjustment layer above it. You can do this by going to Layer>New Adjustment Layer>Hue/Saturation. If you are not familiar with Adjustment layers, check out this tutorial.
- Now play with Hue and Saturation scales until the waves on the photo completely disappear. For this image I found that I need to set Hue at -87 and Saturation at -45 to make any traces of moiré pattern disappear. But remember, you must do this in Actual Pixels zoom level at 100%. Otherwise, if you are trying to adjust luminosity at other zoom levels, such as 33%, you can be wasting your time since the color patterns will not be representative of the real size.
- And now for the final touch, all you have to do is make the 'Dress' top layer visible again.
In my case, these two steps removed moiré without a trace. However, you might encounter cases where there might still be some hint of moiré left. Depending on the image and the strength of moiré effect, the second step might not completely eliminate the waves; in that case you might need to supplement your workflow with additional tricks, such as Clone Stamp tool or Spot Healing Brush tool.
How to Avoid Moiré appearing in photos
Now that you know that removing moiré from images can be tedious and time consuming, you might ask 'How do I avoid moiré while taking picture?' There are several easy things you can do to avoid moiré, but the most difficult thing is knowing that you are getting it on your images in the first place. Since moiré is usually not noticeable on LCD preview screens, it is recommended to zoom in to actual size on at least one image in the series if you are working with fine fabrics or macro shots, especially if you know your camera is prone to producing moiré. Here are some of the steps you can take to avoid moiré if you know you are getting it in your photos:
- Move away from your subject. Moiré often happens when the pattern detail you are capturing exceeds is at the frequency where camera's anti-aliasing filter cannot engage to clean it up just yet. Often when you zoom out or step away a bit from that pattern anti-aliasing filter will kick in and moiré will disappear.
- Get closer to the subject. If you are at that distance where moiré appears and camera's anti-aliasing filter can't deal with it and you can't get farther or zoom out, then get closer or zoom in on the subject. When you do that, the texture frequency goes down (because it gets bigger in relation to your sensor) and then the pattern will be easily picked up by your sensor, since the texture would not exceed its resolution anymore.
- Change your angle. Changing angle can eliminate virtually all moiré because the texture's interaction with the sensor also changes.
- Increase depth of field. If the texture that that produces moiré is not the main subject of the image, try to have a shallow depth of field (make everything around subjects plane blurry) by opening up your aperture. If you are not fluent with aperture settings and depth of field check out this article.
- Two of the main issues that you certainly will come across when shooting with a low-resolution camera (even with a 4K camera in some cases) that records 8-bit video are the moire and banding artefacts. Whereas the latter can be overcome with a unit that simply provides higher bit-depth, certain post-production techniques can help you to reduce the nasty moire patterns considerably.
- GIMP News Feed Contacting Us Unless otherwise noted, The GIMP Website by The GIMP Team is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
- For more about image cleanup in general, see Commons:Images for cleanup.
Interference or other regular patterns overlaid on an image can be introduced by a variety of sources, including:
- Electromagnetic interference in the environment of the device collecting the image;
- Noise in a transmitted image such as a television still due to analog transmission interference or degradation of media;
- The texture of the paper that the image was printed on, particularly if it was printed in a cheap magazine or newspaper.
Hp 620 webcam driver. Attempting to remove these by ordinary image space techniques such as replicating the pattern and subtracting it would be extremely difficult and unlikely to be completely successful. Sometimes interference can be hidden by downscaling or blurring, but this is rarely a satisfactory solution.
Interference or other regular patterns overlaid on an image can be introduced by a variety of sources, including:
- Electromagnetic interference in the environment of the device collecting the image;
- Noise in a transmitted image such as a television still due to analog transmission interference or degradation of media;
- The texture of the paper that the image was printed on, particularly if it was printed in a cheap magazine or newspaper.
Hp 620 webcam driver. Attempting to remove these by ordinary image space techniques such as replicating the pattern and subtracting it would be extremely difficult and unlikely to be completely successful. Sometimes interference can be hidden by downscaling or blurring, but this is rarely a satisfactory solution.
A simple and effective technique for dealing with these problems is to identify the interfering features in the power spectrum image produced by Fourier analysis, eliminate them, and convert back to image space. This tutorial shows how to do this using some widely available tools.
Tutorial for Photoshop[edit]
First, go to Alex V. Chirokov's Archive page and click the link labelled 'Download new version of FFT/IFFT Photoshop plugin'. Copy the files from the archive into your Photoshop plug-in directory. Start Photoshop.
For our sample image, we'll be using this lovely photo of a rose which mysteriously became striped with an interfering pattern of diagonal lines (actually, I took Image:Rosa_Gold_Glow_2.jpg and added the interference myself).
Moire Pattern Photoshop
First, we'll need to edit each channel separately (unless the image is grayscale or monochrome, then the manipulations can be done directly to the image). Click the 'Channels' tab, and for each of the Red, Green, and Blue channels, select the channel, select all, copy its contents, and paste into a new image. Convert all three new images to RGB mode using Image→Mode→RGB color. Flatten all three new images (this is important - the resulting image will have distorted brightness/contrast if you don't do this).
On all three images, select Filter→Fourier Transform→FFT. Next, select one of the images and zoom it (it doesn't matter which one). You should see an image full of green and red noise, with a few bright spots in the red channel. We need to figure out exactly where all the bright spots are. Go to the channels tab and hide the Blue and Green channels to see the spots better. If it is still difficult to see them, select Layer→Duplicate Layer to duplicate the layer containing the FFT image, and click OK. Next, with the new layer selected, go to Image→Adjustments→Levels, switch to the Red channel, and drag the black (low) slider up until each of the bright spots in the image is clearly visible. (If you're curious about why the FFT images are so colorful, it's because it's encoding the phase shift, needed to later reverse the transformation, in the hue of each pixel.)
On the red channel, use a round, pure black brush of appropriate size to erase all of the bright spots except the one in the middle. Don't be afraid to erase too much of the area around a spot - it usually doesn't hurt anything as long as you're not too close to the center. In this sample image I spotted 8 bright spots, but there can be as few as 2. Copy this layer to a new channel on top of each of the other two images, making sure that it's lined up over the bright spots in all the images.
Finally, hide the middle layer (the one with the red channel adjusted) from view, choose Layer→Flatten Image, and say 'OK' to the dialog telling you that hidden layers will be discarded. Make sure no bright spots are left other than the one in the middle. Flatten the other two images as well. Then, choose Filter→Fourier Transform→IFFT. You should observe greatly reduced interference in all three channels.
To recombine the channels, simply select the correct channel in the original image and copy the contents of the edited image over it using Select All, Copy, switch images, Paste. It may be necessary to adjust brightness/contrast. We now have a much nicer looking rose. It's not quite perfect though, being slightly blurrier than the original and having some subtler artifacts left over — it's always best to find a clean copy of the original image if possible.
Sometimes bright lines (nearly always vertical and horizontal) may appear instead of single spots. Messenger for windows 10. Also, sometimes a particular bright spot may correspond to a legitimate part of the image rather than a defect. Use trial and error and frequent conversions to and from image space to determine the right information to erase. Even though you will normally want to avoid editing near the central 'axes', the bright spots might sometimes appear on them too. Remove the spots, but a bit more carefully.
Tutorial for Gimp[edit]
First we have to install all the necessary software. All you need is available for free on Internet.
- Install Gimp, if you don't have it. Then, respective of your operating system:
Linux[edit]
You have to download and install:
- The gimptool utility: it should be within Gimp. Several Linux distributions put it in a different package. On Debian and Ubuntu it is called libgimp2.0-dev
- the fftw library: you can get it from www.fftw.org. It is available on Ubuntu and Debian repositories as fftw3 and fftw3-dev
- the Fourier Gimp plug-in, you can get it from http://people.via.ecp.fr/~remi/soft/gimp/gimp_plugin_en.php3#fourier. There is no package for Debian/Ubuntu, you have to install it from the source.
Windows[edit]
- To install the Fourier Gimp plug-in download the 'Binaries for Windows' from http://people.via.ecp.fr/~remi/soft/gimp/gimp_plugin_en.php3#fourier and extract its contents into the Gimp plug-ins directory (.gimp-2.xplug-ins in your user directory or C:Program FilesGIMP-2.xlibgimp2.0plug-ins).
- Restart Gimp, if it is running.
| First open the image; it will be in RGB format. We want to be able to manipulate the RGB layers separately (unless the image is grayscale or monochrome, then the decomposition of channels to layers can be skipped and the manipulations done directly to the image). In order to do so, right-click on the image and choose Image→Mode→Decompose (see screenshot on right). For the latest version of GIMP, right-click and select Colors→Components→Decompose. Gimp will create another gray-scale image having the RGB as different layers | Open the image |
| Choose RGB and press OK (see screenshot on right). This way you will get the decomposed picture. | Choose RGB |
| Select the window with the new picture, go to the layers window (if you can't see it go to File→Dialogs→Layers and it will appear) and hide all but one layer clicking on the eye to remove it. Then select the remaining layer. On the screenshot on the right I have isolated the blue layer. Now you can work on one layer without influencing the others. It is also recommended to apply 'Remove transparency' from the layer's right-click menu to each layer, as transparency is not needed and only distracts when editing. | Let's move to the frequency domain |
| After you have finished editing you have to convert it back to the standard domain performing the inverse FFT. Right-click on the picture and choose Filters→Generic→FFT Inverse as shown in the picture on the right. Do the same for all the three layers. | and now let's come back to the spacial domain |
| After you have edited all the layers (remember to perform the inverse FFT on all of them!) you have to get your RGB picture back. Right-click on the picture and choose Image→Mode→Compose (see screenshot on right). Here is your picture! | Let's come back to the RGB picture |
See also[edit]
External links[edit]
- GIMP: Remove Coherent Noise (Wikibook)
