Camera induced moire
A good question would be: “Is it possible to prevent this from happening during the photography stage?”. While no camera settings will save you from moire with 100% probability, some of them will make your life much worse as they will facilitate the process. But this should only concern you if you work with jpeg images. If you get raw images, you have more flexibility. But jpeg images can be covered in moire patterns created by a camera processor. It happens in two cases: first is when a camera sharpens images, and second is when the image size gets reduced by a camera. Both cases might lead to moire patterns appearing when no moire was present in the original, raw image. Quite a peculiar phenomenon! But the solution is quite simple: change the camera settings so that the image size doesn't get reduced and no additional sharpening is applied to the images. Let's see some examples.
This image is a fragment of a medium-sized jpeg from a pretty good camera. Its size is 2432 by 3648 pixels, while the original would be 3840 by 5760 pixels. It's not like it is too sharp, but there are visible moire patterns all over the sweater. This kind of moire is very hard to fight. When I asked the head of photography to change all the camera settings so that the images would not get resized, and they did that, the problem was solved. So if you get a lot of moire in your images, check the size, it's probably the reason why moire appears. It has nothing to do with a camera sensor meeting a fine pattern, it's just a faulty camera interpolation mechanism.
This image is not some kind of medium jpeg, it's size is original. But it's way too sharp for an original image, which means it was either processed with a raw converter with some serious sharpening settings or maybe a camera processor did it because it was set to make images much sharper. It might not look like a big deal, but when you resize images like this one from 5000 pixels high to 1000 pixels like you usually would in
Okay, I hope you've got my point. Which is – if you work with jpeg images, make sure they are neither resized nor sharpened by the camera because it will bring you more trouble than joy. Now let's proceed to other kinds of
There's also a special kind of moire that you might encounter when viewing images, but in reality, it doesn't exist. You only see it only in some special circumstances, and it only happens with some fine patterns in the images, especially thin stripes and checkers.
This dress, for instance, is totally devoid of moire when you look at it at 100% scale, which is the only real visual representation of an image. But if you start zooming it out, you'll see that when the stripes become too small to be distinguishable, a weird rippled pattern appears. Would it be correct to say that a moire pattern appeared on the image? Not really. Because when we look at the image at 100% scale, there is no pattern. So it is only possible to claim that a moire pattern appeared on the screen, not on the image. In terms of retouching, it means that there's no moire, therefore you shouldn't do anything with it. Before you even start thinking about retouching moire, make sure you see the image at 100%. If it's fine at that scale, there's no moire, it doesn't exist in the real world.
Seriously, I thought it was obvious, but my opinion changed after watching a couple of tutorials that explained how to fight the preview
But sometimes, after you resize an image, the moire patterns might appear for real.
Just as before, interpolation moire doesn't appear in the original images. It appears in the resized images because there's some fine pattern that can't really be displayed properly at a particular image resolution in pixels. Like this dress from the example just before. It's really fine at 100%, and it doesn't look bad if I resize it to be 1000 pixels high. The stripes are still clearly visible, there's nothing weird going on. But if I had to make it really small, like 700 pixels high – it won't work so well. You'll see a moire pattern, and this time it's for real – because it's there at 100% scale. Nowadays online stores use bigger images than that. A lot of people use mobile phones with high-resolution screens, there's also a bunch of people that use Apple products, which means retina high-resolution displays. You can't really get away with images 700 pixels high nowadays, it's not enough. But the first online-store I worked in produced images that were quite small – only 600 by 600 pixels. The interpolation moire was quite common back then. But even now, it can still occur in bigger images, depending on the pattern.
This jacket close-up is prone to interpolation moire because of its texture. It's very small and grainy – this kind of material will often give you a moire pattern after resizing. I'll change the image size to 1000 pixels high and there it is – a weird recurring motif where a different texture should have been. What can we do? A good option for a close up would be just cropping it so that the fine texture is larger in the final image. This way it can be resampled properly.
There are, of course, other methods. The easiest one is to change the interpolation algorithm that is used for resizing. When you access the Image Size window, there's a bunch of resizing algorithms you can choose from. The most reasonable option is the Bicubic, best for reduction, as it makes images less blurry when you resize them. But it might give you a moire pattern. Try switching it to the Bicubic for smooth gradients, and you'll see the difference. No moire appeared after resizing!
Let's see if the same approach will work on the previous image, the one with the striped dress. I'll make a copy of an image resized with the Bicubic Sharper algorithm for a comparison, and then go back in History and resize to the same height, which is 700 pixels, but with the Bicubic algorithm for smooth gradients. Now I can use this image to compare with the previous one, but first I'll make sure the scale is 100%. It is pretty evident that the moire pattern is not so evident in the latter image, which means simply changing the interpolation algorithm works well enough. The problem is, it doesn't work all the time.
This polo shirt gets all covered in moire even if you use the smoothing interpolation algorithm. So let's see if there are other methods of dealing with this issue. One of the best things you can try in this case is stage resizing. The deal is that when the original image is very big, almost 5000 pixels high, and the final image is too small, like 700 pixels high, and when you go from 5000 to 700 in one go, the result might not be perfect. But if you do it in a series of steps, each reducing image size a little bit, you might get a better result. Let me show you how it works. Once again, if I change the image size in one step, I get a moire pattern all over the polo shirt. But let's see what happens if I change the size gradually. I'll record an action straight away to save myself some time. I'll call it “stage size” and the only command it will contain is the Image Size. There, you should switch from pixels to percent, and put 90 in width or height, and choose the Bicubic algorithm for smooth gradients. These settings will change the image size to 90% when applied. But this is not much, so I'll duplicate this step two times. Now there are three commands that do exactly the same thing. I'll test this new action on the polo shirt image to see if it works. As it only makes the image smaller a little bit, running it once doesn't necessarily solve the moire problem. I'll run the action one time and then change the image size manually to 700 pixels high, and you'll see that moire appears despite the efforts. But what if I run the stage size action twice? Let's see. I'll do it two times and then change the image height to 700 pixels. And moire is no longer tainting the polo shirt, well done!
Stage resizing is a great way to fight interpolation moire, as it's quite harmless unless you get carried away and resize the image too much so that you'd have to stretch it afterward. Just watch it with the size and you'll be fine.
Now let's discuss real moire. Not the
There's a spot of colored moire on this jacket, so let's see how we can remove it. If you've paid attention to the section of the course that is dedicated to color correction and Adobe Camera Raw, you probably remember that there's a Moire Removal slider within the Adjustment Brush panel. Let's check it out. To access Camera Raw from Photoshop, I'll press Shift-Ctrl-A. Then I'll press K to access the Adjustment Brush. I'll find the Moire Reduction slider and set its value to plus 60 or something like that and then paint over the moire in the image. Not bad, huh? The moire pattern is gone now.
There's actually an easier way when you encounter colored moire on single colored surfaces. You can just colorize it with the Brush in Color mode. I'll set my brush blending mode to Color, pick a sample from an area nearby and paint over the moire pattern. A couple of seconds – and it's completely gone. At this point you might think that fighting moire is a piece of cake, but wait till I get to the dreaded monochrome moire.
There's another way to reduce colored moire via ACR I haven't mentioned in the video. Go to the Detail tab and set the Color slider in the Noise Reduction panel to 100. If the moire pattern is not very severe, it will be significantly reduced. And it will save you time on manual colorizing.
Colored moire might not be completely eradicated with this method, but when you're in a rush, it will have to do. The same is true about using a brush in Color mode when in Photoshop: if the ripples are not blue and yellow, they don't attract so much attention. But if you're trying to apply color and it just gets worse, you're probably having a bad case of monochrome moire.
Unlike colored moire, monochrome moire is not about color. It means that you can't colorize it no matter what. It exists in another domain, which is the tonal range. It doesn't mean that the monochrome moire can't be colored at the same time. It's just that we have to distinguish between these two kinds of
This is a very good example of monochrome moire. If I tried and used a colored brush to remove it, it wouldn't work at all. The deal is the wavy pattern has different brightness levels, which are not affected in the Color blending mode. This kind of moire is etched deeply in the image, no matter how you look at it. Removing it is hard as hell, especially when the item's texture is complicated and cannot be faked. But if it can – well, even horrible moire patterns like on this image here can be removed in no time. As this is a close-up, I'll crop it, resize to something more fit for an online store, like 1500 pixels height. Then I'll switch to the Quick Mask mode and use a soft black brush to select the moire covered areas. Then I'll quit the Quick Mask mode and use the Gaussian Blur filter to get rid of the ripples – don't be shy, the Radius should be high enough to remove it all at once. And after that I'll just add some noise with the Add Noise filter – about 2.5 creates a texture that closely resembles the original one.
The aforementioned method of moire removal is, of course, very crude. It can only be used on textures that are easy to fake by adding some noise. But there are other methods that are more sophisticated, just keep on reading and watching.
You can download the images for practice purposes from the gallery above. Each thumbnail is linked to the respective hi-res image, just click on the thumbnails you need to open them in a separate window. You can right-click and "Save link as…" to download images without having to open them first.