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Background cleaning

Cleaning a dirty backdrop is no fun at all

When you don't have to isolate objects or models or whatever you're working with, you have to retouch the background instead of removing it. It mostly happens with models, but objects can be like this, too. If there are no specific demands about the background's color and tone, you're good, because you'll mostly have to clean it and that's it. But some companies want their images to look the same and they say: “Okay, so the background should be light gray, neutral, from 245 to 250 on average”. This is actually worse than isolation because what comes from photographers can be quite different in terms of background exposure. If you can just isolate the background and make it, let's say, 245 solid gray, and restore a natural shadow, it would be faster than trying to adjust the image so that it fits some background tone range. You'll find out that when photographers shoot white items, they sometimes close the diaphragm a bit to avoid overexposure. It makes white items and the background darker. And when they shoot black items, they do the opposite, so that the items don't come out underexposed. So you'll be getting different images with different backgrounds, and trying to make them even is crazy hard. If you concentrate on the background when color correcting, you'll find out that it doesn't do any good to the objects or models. And the deal is that concentrating on the background while ignoring the objects is probably the most stupid thing you can do in catalogue retouching, because the approach should be exactly the opposite. We may use the background as a tool when color correcting, because if it has a weird tint, it most probably means that the white balance is wrong. When it's too dark, the object is probably underexposed, and vice versa, and so on. But maintaining a specific background color and nice contrast and exposure on all the objects at the same time is like sittings on two chairs at once – an impossible trick.

Models are easier. The setup on model photography stations is usually very strict. You can't really play around with the camera settings when you have a living person in the frame. Models don't get isolated very often, they mostly stay on some neutral background. So if you don't have to remove the background, you have to clean it. And it really matters how dirty and worn it is if that's the case. Cleaning dirt is your task number one, because you can't really avoid it.

A funny thing – most of the tutorials on background cleaning presume you have to isolate the background from the model or the object and only then will you be able to clean it. The necessity of isolation renders the whole idea of using natural backgrounds instead of some solid color useless. Because isolating and cleaning is actually longer than isolating and filling. To benefit from natural backgrounds, we have to clean them without isolating whatever is standing or lying on them. Otherwise, it doesn't make sense, at least in catalogue retouching.

Not mentioning the fact that isolation in mass image productions has to be performed on the clean backdrops, or it might take too much time, more than reasonable. But we also realize that a background used for shootings cannot be maintained spotless clean at all time, even if it's cleaned daily. Because when it's used, it gets dirty in the process.

Just keep in mind, that when I say “a dirty background”, I don't really mean a situation when a model or an object is literally standing in the dirt, and the only way to separate it from dirt is the good old Pen Tool isolation. So before we learn how to clean backgrounds without wasting time on isolation, let's work on definitions. What's a clean background and what's a dirty background?

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This belt was shot on a spotless clean background. When I access the Levels and drag the leftmost slider to the right, it doesn't reveal any dust or dirt. There's just one tiny dot, which is next to nothing. Working with backgrounds like this one is awesome, but it only happens a short while after the background has been changed. This purity doesn't last long. In a couple of days or even hours it might get a bit dirty.

This background looks more or less clean, but it's in fact quite worn and it's also scratched. You might not notice that, especially if you have a high contrast monitor, but I know how customers love to push their laptop screens away from their faces so that they can see all the details. So, a background like this requires some cleaning just to make sure there are no scratches or anything like that.

This background is seriously dirty. It's not like it's a big deal, but you have to clean it thoroughly. Maybe it's the right time to learn how to do it properly. I hope you remember the Dust & Scratches trick we use when we clean small trash from smooth surfaces. A typical studio background is a smooth surface, which means you can use the same technique. In case you forgot, I'll remind you really quickly. You use some blurring filter like the Dust & Scratches to get rid of the dirt on the whole image. Then you set the History Brush source at this step, and then you click on the step just before that to undo the filter effect on the image. Now if you use the History Brush, it will be applying a Dust & Scratches effect wherever you use it. This is a good method of dirt removing, if your surface is smooth, of course.

It's just that the Dust & Scratches filter is not the best tool to use when you deal with backgrounds. If I used a Radius big enough to smudge all these huge chunks of dirt, like 30, it would also severely damage the shoe. So if I do that, I have to be very careful with the History Brush as I come close to the edges. If I touch the shoe, it gets ruined.

But if I used the Surface Blur filter instead of the Dust & Scratches, I would be able to avoid this unpleasant side effect. At Radius 30, Threshold 30, the dirt is gone, but the shoe still has its edges more or less the same. I shouldn't, of course, use the History Brush directly on it, but I won't ruin the shoe if I come close. This is much better than the Dust & Scratches, but I must admit that the Surface Blur is a bit slower. Nevertheless, it's a great method, but if you want to record an action straight away and use it for all your backgrounds if they look about the same as this one, wait a bit. In the next video I'll explain how to get rid of posterization caused by the use of filters like Surface Blur and Dust & Scratches.

This background is terribly worn, and you can see multiple stiletto heels indentations. The deal is that if you're not isolating, backgrounds should not be so worn and dirty. Photographers should change them more often, as it requires a lot of time and effort on our side of the table. The paper is even torn in one spot, which is not a good thing at all. You can still try and use the Surface Blur with the History Brush trick to clean the whole thing. It will remove all the indentations, all except for the tear, which can be easily dealt with if you switch to the Spot Healing tool. But unfortunately, the indentations will not be removed completely. If I use the Levels to darken the image, you'll see that the background looks spotted.

You can't really use the Surface Blur for background cleaning all the time. It's pretty efficient when you have smudgy dirt, but as it's supposed to preserved edges, edgy dirt will most likely stay. When I tried it on the image with the shoe, Radius 30, Threshold 30 was enough. But this image has some holes that refuse to be blurred. You have to increase the Threshold to 60 to get rid of them. Pins, no matter how thin they are, will also remain, just become less visible. And you know what, if I just used the Dust & Scratches filter with Radius 15, it would eradicate all the holes and pins and everything. Just make sure you stay away from the edges.

But once again, if I use the Levels to darken the image, you'll see that color transitions are not smooth anymore, you can see a visible edge where no edge was present in the original image. And here we come to the problem number one in background cleaning – the posterization.

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So, posterization or banding. That's what you get when you try to clean dust and dirt on a large surface by using filter like Dust & Scratches or Median (which is basically Dust & Scratches with Threshold = 0), or any filters from the Blur group.

When you get to see a typical Photoshop tutorial that teaches you how to clean all the dirt with the Median filter, the question of posterization is usually carefully avoided, as if it doesn't exist. But we'll deal with it head-on, as there's nothing worse than an image covered in weird stripes. Besides, if you have your image severely posterized, there might be no way back.

Posterization

If you use filters like Dust & Scratches or Surface Blur, you might encounter posterization in your images. Posterization, or banding, is a very unpleasant visual effect when instead of a smooth gradient you get abrupt tone changes visible to the naked eye.

I used Dust & Scratches filter on the right image and then darkened it to make the effect more visible

Imagine that instead of cleaning the background only where it's necessary, I would just select it all and apply some filters to it. Like the Dust & Scratches and also some Surface Blur. Try it, and despite the fact you might not be able to see it on your monitor straight away, posterization will be present in the image. Just access the Levels and move the leftmost slider right till it hits about 210. Instead of smooth transitions, you'll see weird colored blots. In the original image state it's not so evident, but it's still there, and this posterization won't go away when you resize the image. Fighting posterization is not easy, so the best method here is actually prevention.

The best kind of prevention is not using any filters or commands that might cause posterization in the first place. When you color correct in Photoshop by using Levels or Curves, you can make it appear without even noticing. This is why we mostly color correct using Adobe Camera Raw plug-in and avoid any changes of the tonal range in later stages of retouching. What you should avoid as well is using the Dust & Scratches or the Surface Blur on the whole background. One thing is use blurring in the History Brush mode, when you apply the blurring effect locally. Blurring the whole background is another thing – you get it posterized, and heavily, if you're not careful enough. But even local posterization is an annoying problem, so let's now learn how to deal with it if you can't refrain from using blurring filters.

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The first useful trick is this: convert the image to 16-bit mode, apply whatever you were going to, like the Surface Blur filter, and then convert it back to 8-bit. It sounds like a total waste of time, because if our image is in 8-bit since the beginning, converting it to 16 bit doesn't bring in any new tones. But it does matter when you use a posterizing filter like the Surface Blur. Let's compare two images. I'll convert the first one to 16-bit and then I'll apply some Surface Blurring to it. Then I'll convert it back to the 8-bit mode. On a separate layer, I'll apply the same amount of Surface Blur. And then I'll adjust the Levels of both layers so that we would be able to see the resulting posterization well.

Without any questions, 16-bit layer looks much better. This mode is more demanding to your machine resources, but it's not like you have to use it all the time. We don't work in 16-bit in catalogue retouching because we're satisfied with the quality available in 8-but mode, plus we are not able to save jpegs in 16-bit anyway. But converting there and back can be a very useful trick if you're trying to avoid posterization.

There's also another way how to make image less posterized in the process. If you apply a massive amount of Noise before using blurring filters, the result will be much better. Especially if you add a bit of Noise after the blurring as well.

Let's use all the methods I've mentioned at once and see how it helps. I'll convert this image to 16-bit mode, apply 3% of Noise, use the Surface Blur 30,30 and the Dust&Scratсhes 15,0, and finally, apply more Noise, but just 1% this time. Now I'll convert it to the 8-bit mode and that's it. As for the other copy of the image, I'll only use the Smart Blur and the Dust&Scratches with the same settings as before, but without any precautions. Now I'll apply some darkening to both images to make the resulting posterization more visible, and you can see for yourself: one of them is heavily posterized, while the other one looks very decent. It is a bit grainy, but the effect will be reduced after resizing, so there's nothing wrong with that.

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Background cleaning action

The background cleaning action can be found in the action set above. But you can write your own using the instructions given in the video:

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Keeping all this in mind, let's now record a background cleaning action that won't cause heavy posterization. First thing it has to do is convert the image to the 16-bit mode, than use the Add Noise filter to add 3% of noise to the image, then Surface Blur and then the Dust&Scratches to make sure all the dirt goes away. Then add more noise, like 1%, and convert the image back to the 8-bit mode and set the History Brush source right at this step. Then go back in History by 6 steps – before doing anything. That's it. Now when you run the action, it won't change anything in the image, but if you use the History Brush anywhere on the background, it will remove all the dust and dirt without causing much posterization, which is actually very nice.

We didn't care about that before when we use the same technique on human skin and on objects, because when a surface is relatively small, no one will notice even if it gets a bit posterized. But if you're dealing with something as huge as a background, you have to make sure you preserve all the smooth transitions.

As for the Dust & Scratches and the Surface Blur settings, these two steps might need some tweaking on your side, because the settings might be too much or not enough for your particular images. So feel free to adjust the action so that it works better.

Background cleaning principles really depend on the images you are working with: their size, how dirty the background is initially. But if you don't isolate and clean background instead, it shouldn't be really dirty. It shouldn't be dirty even if you isolate, but if you don't, it should be especially clean. Preparation of the background is important, too. So if you have to deal with dirt all the time and spend too much time doing that, it's the photography station that has to change something.

When you clean the background, make sure there's no dirt in the shadow of the object. The deal is that shadows can conceal dirt pretty well, so make sure you look there first. You can get rid of all the dirt and scratches with the action we've recorded a while ago. It works pretty well and you can even remove the piece of paper stuck to the sole with the same method, as the whole area is mostly out of focus. If there are any spots left after that, feel free to do some smudging with the Mixer Brush, or even use the Spot Healing Tool.

If a model or an object drops a hard shadow on the background and you're not supposed to blur it, you'll have to change the settings of the background cleaning action. The Surface Blur Threshold is responsible for the feathering effect, so if you change that to 3 instead of 30, the shadow will stay in place. If that's not enough, you'll have to reduce the Dust & Scratches Amount, too. All these changes will make the action less effective, but you can always use the Spot Healing Tool and the Mixer Brush if there are any spots of dirt left.

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Instead of isolating the background from the object/model and blurring and doing other things to it on a separate layer, it makes perfect sense to apply the blurring effect locally with the history brush, as it's evidently much faster and easier. You have to be careful as you come close to the edges, that is, not to smudge them as well, but it doesn't require as much precision as when you're isolating.

It's important to understand that the more blurring you apply, the more severe posterization you get. To keep it to the minumum, it makes sense if you smudge huge chunks of dirt and things like that with the Mixer Brush before using the background cleaning action. With this precaution, you'll be able to apply blurring filters with less cruel and posterizing settings, as you only need big radii when you have to eliminate big dirty spots. By the way, the Mixer Brush itself doesn't bring as much posterization as you would expect from such a smudging tool.

One last thing. As we're doing everything we can to fight banding, there's a question that arises pretty naturally: “Can we use the frequency separation technique to clean backgrounds? Because you know that when the frequencies are split, you can protect all the small details by preserving them in the high frequency layer. With all the final details safe, there will be no banding”. Well, yeah. That's true. You can run the frequencies splitting action, then smudge all the dirt on the low frequency layer, then switch to the top layer and use the Clone Stamp as much as you want, no banding and all. But there's one huge flaw of this method: you have to clean the whole background twice. Double amount of work – first you clean the low layer and then you clean the high layer. So in my opinion it's absolutely worth using an action that applies smoothing filters and noise, as you're able to clean the whole thing just once and for good. So the splitting method should only be used when you can't use the smoothing method – in case the background cannot be smoothed because of its texture. If you can't fake it by using noise, you can't smooth it, that's pretty much evident.

Content-aware Scale & Fill

When you don't have to isolate, new problems arise depending on how careful photographers take aim when shooting. When you crop images, most of the time you're supposed to make sure that objects or models are centered and are not leaning to any of the sides. So if photographers are not careful enough, you might encounter 2 unpleasant situations: in the first one you won't be able to center a product, because you won't have enough background to do so, and in the second one won't be able to rotate a product, and in both cases some blank canvas will be added to your images after you align them. Let's see what exactly happens, why, and how to fix it.

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This model is in the center of the image, which is good, but she's leaning to the left. So I'll select the whole image and rotate it clockwise. Let's imagine that I also have to crop the image and the crop ratio has to be 2:3. I'll use the Crop Tool for that and I'll specify the Ratio in the settings beforehand. I have to crop the head out, too. Now when I apply the crop, you might not notice that immediately with the background being so light, but there was not enough of the original background, and some parts of the newly cropped background are filled with solid color from the background swatch. To make this more evident, I'll undo the cropping and rotating steps, change the background color swatch to black by pressing X and crop once again. Now you can see for yourself: the image is filled with solid black in the upper left and the lower left corners. It wouldn't have happened if the photographer just had taken a couple of steps back. There would be more background around the model and it wouldn't be replaced with black upon rotation. But this kind of thing happens a lot with model shooting, because photographers are not thinking about retouchers' convenience when they shoot. It's good to let them know if that happens, but we also need a quick way how to fix this issue in Photoshop. Because it's evident that you can use the Clone Stamp and that will help, but there's another efficient method that takes less time and you don't have to be very careful when using it.

So, here it is. Select the solid-color filled areas with the Polygonal Lasso or any other selection-making tool, and make sure it's not too tight. Then access the Fill window by pressing Backspace and pick the Content-aware from the options list. Press Enter and the black areas will be filled with what Photoshop finds appropriate in this particular case, depending on the surroundings of your selection. I'll use Levels to show you that the whole background looks consistent and there are no seams or weird-looking areas anywhere. So if you don't feel like stamping, you can use the Content-aware Fill to your advantage.

When models are not static, when they are walking around for a more lifestyle look, it might be hard for photographers to catch them in the center of the frame. Not all the online-stores require their models to be centered, but it's a more or less typical demand, so there's a high probability you'll have to take care of it. This model is not leaning to any of the sides, but after I crop the head out and move her to the center of the image with the Crop Tool, a part of the background gets filled with solid black. Once again, you can use the Clone Stamp in situations like this, but why not trying more advanced Photoshop algorithms? The whole content-aware thing is with us since Photoshop CS5, and it was a breakthrough back then – for a reason.

Use the Rectangular Marquee Tool to make a rectangular selection that includes everything in the image but the black stripe. Now press Shift-Ctrl-Alt-C, which is the shortcut for the Content-aware Scale command. It can also be accessed from the Edit menu. You'll get the usual Photoshop transform interface, but it's a bit different. Look what happens when I extend the selection to the left. The black stripe gets filled with the original background, but at the same time, the model doesn't stretch. She is just shifting towards the left. I can give her a little pull from the right to place her in the center. The Content-aware Scale algorithm works pretty well when you have enough background around the product, and it lets you fill any background gaps easily. Just be aware that it might distort models if you pull too far or if there's not enough background around. But most of the time it works, and it works fine.

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Both content-aware fill and scale can be used to fill gaps in the background after rotation and cropping, but the content-aware fill is also good when you need to center something and there's not enough background on either of the sides. It's a good idea to remind photographers not to come too close to models though. If an image has enough background around the model, you wouldn't need to fill any gaps. But that is only true when there's enough background in reality. I've seen many photoshoots where photographers used a relatively small backdrop. In cases like that, your only option would be adding more background in all directions. Doesn't happen in big studios though.

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.

Next chapter: Moire reduction

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