The Auto-Align Layers command
The Auto-Align Layers command
In this chapter, we are going to be covering three commands; two of them are located under the Edit menu. The first, Auto-Align, layer takes multiple shots of the same scene and geometrically distorts those images so that the stationary elements align with each other. That way you can mask out any moving elements or you could mask together people in the same scene. I'll show you a couple of examples. It's an extraordinary command quite frankly. Auto-Blend layers is perhaps even more magical. What it does is once you get done aligning your layers then this command will automatically adjust the exposure of all the images.
So that the brightness and contrast and colors match each other and then it goes in there and automatically masks the images together. It's an extraordinarily intelligent command, not a command you'll use very often, but a technological wonder. Then we have a command that's essentially a combination of the two. Under the File menu, you go to Automate and then you go down to this command here Photomerge. Photomerge goes ahead and stitches together multiple images to create a seamless panorama. That's what it does from your perspective. From Photoshop's perspective it just applies the Auto Align layers command and follows it up with the Auto- Blend layers command and that's it.
Just those two commands working together ends up stitching together seamless panoramas. This is the command you'll use the most often but I want to show you what's going on under the hood in advance because you may find lots of uses for Auto-Align layers and every once in while you may find Auto-Blend layers useful as well. So, we are going to start off with a fairly mundane example here, it's called Colorado capitol.psd and it features the capitol building in Denver, Colorado. I took probably about five shots of this scene actually because there were cars and people in the foreground here and I wanted to get rid of them.
I ended up coming up with two shots that accommodated each other, that is, that accounted for each other's weaknesses. So, I've got this one called another shot on top here. Both of these layers should appear selected when you open the image, by the way. This image that we are looking at has this minivan in the middle of things with some blue gunk on the grill. I don't know if it's paint or tape or what it is but I don't want it in my shot. Then in the Background, if you turn that layer off for a moment, you'll see that we pretty much have all that area accounted for so there is no car in that exact same position.
However, there is another car over here on the left-hand side. If I were to go ahead and turn this another shot layer back on and set it to say 50% Opacity by pressing the 5 key. You could see well a couple of things. First, of all the cars almost touch each other so we are going to have to be careful about the masking. But here's the bigger problem, the images aren't aligned with each other. And that's because of course I didn't have a tripod. I'm just shooting these images with my Olympus E30, which is a great SLR, but we are relying on me to remain stationary and I wasn't quite stationary as you can see.
So, what we need to do, one of two things. I could just try to move these images and manually transform them, which would require possibly a little bit of scaling, maybe some rotation as well, maybe a little bit of distortion in order to get these images lined up, or I could just let Photoshop do it, and Photoshop is killer at this. So, as long as you have two images that were shot relatively close in time to each other, so that the lighting is similar and not too many objects are moving - if you've got a ton of movement or you don't have enough good geometric background information then the command will fail and we'll see an example of that.
But for now, it's going to succeed like crazy where these images are concerned. First, change the Opacity of another shot to 100% by pressing the 0 key. Now, I'll Shift+Click on the background so that both layers are selected; very important. There's two ways to get to the Auto-Align layers function. One is to go up to the Edit menu and choose the command so, that's pretty obvious. But there is this hidden way and I just want you to be aware it exists. If you have the Move tool selected then you'll see up here in the Options bar these little face icons right there.
If you click on them you invoke Auto-Align layers. What this option is doing here? I have no idea but there it is. Go ahead and click on it or just use the command from the Edit menu and then you're presented with a few different distortion options. What I am going to tell you to do is upfront just go ahead and click on Auto. Unless Auto goes wrong you don't need to worry about these other options that are available to you but just for the record here. Perspective allows Photoshop to go ahead and scale and rotate and distort the layers.
By the distort I mean a four point distortion so that it's moving the corner handles for each one of the images with respect to each other. Cylindrical and Spherical go even farther and they are primarily useful for panoramas. So when you're using the Photomerge function you might want to select one of these two and I'll explain that later. Collage allows Photoshop to scale and rotate the layers but it can't distort the layers. So, it can't do a four point distortion like Perspective can, and then Reposition, all it does is just move stuff around.
So, you'd only want to use Collage or Reposition if you're trying to protect your images and you don't want to apply any distortion. Then we'll drop down here to the Lens Correction options. You can apply automatic Lens Correction on the fly so if you have some Vignettes that you need to remove you could go ahead and turn that check box. If you're worried there might be some Geometric Distortion in the scene then go on ahead and turn on the second check box. I usually go ahead and turn on this second check box by the way. There are no vignettes to remove, nothing really of merit, anyway. But you never know about Geometric Distortion, it's usually worth giving that a try.
So, I'll go ahead and select Auto and Geometric Distortion and click OK and then you wait for Photoshop to do its thing. So, first it tells me it's aligning layer 0, which is the Background layer, and then it's aligning another shot, which is the top layer and we end up getting this effect right here. All right, I am going to press the M key to switch back to the Rectangle Marquee tool and let's take a look at what Photoshop has done. If I turn off the top layer to reveal the bottom layer. Check it out, look how well they aligned with each other. That's absolutely stunning.
I'll go ahead and zoom in so that we can see this a little more up close and personal. For example, take a look at that street sign right there. If I turn the top layer on. It just moves ever so slightly, you can see it just shift like a pixel and I am not even sure it's shifting. Sometimes, when you're zoomed out inside of Photoshop things appear to shift that aren't actually shifting. So, let's go to the 100% view size which is the best indicator and I'll turn off the top layer. You can see things move down just a little bit, turn on the top layer things move up. One of the reasons that's happening by the way is that Photoshop's not just trying to align.
Let's say the street sign and the ONE WAY sign and the pole and the streetlights and this little security camera and all that jazz. But it's also trying to align the background building and it's trying to align all of the leaves on all of the trees. So, it's a lot of work. What it ends up doing though is not paying attention to the cars at all. It can't find this white van in the layer 0 layer right there. So, it doesn't even try to align it. It can't find the back end of this blue car in the top image so it doesn't try to align that either.
So, it just throws out anything that's moving inside the image and attempts to align the stuff that's stationary. All right, having done that we are going to go ahead and blend these two layers together in the next exercise.
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