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Manually Stitching Panoramas Together
Stitching panoramas together in Photoshop is fairly easy, if you follow these two simple rules before you shoot your pano: (1) Use a tripod to keep things level. That's not to say you can't shoot panos handheld, but the consistency a tripod brings to panos makes a world of difference when you try to stitch the photos together. And (2), when you shoot each segment, make sure that part of the next segment overlaps at least 20% of your previous segment (you'll see why this is important in this tutorial). First we'll look at manually stitching panos together, and then we'll look at the automated version later in this chapter.
Step One
Open the first segment of your pano. The photo shown here is the first of three segments that we'll be stitching together.
Step Two
Next, go under the Image menu and choose Canvas Size (or in CS2, press Command-Option-C [PC: Control-Alt-C]). In the capture shown in the previous step, you can see the width of the first segment is about 5'. We're stitching three segments together, so we'll need to add enough blank canvas to accommodate two more photos of the same size, so make sure the Relative checkbox is turned on, then enter 10' as the Width setting. This extra blank canvas needs to be added immediately to the right of your first segment, so in the Anchor grid (at the bottom of the dialog), click on the left-center grid square. Then, change the Canvas Extension Color pop-up menu to White.
Step Three
Click OK and about 10' of white canvas space is added to the right of your photo (if it doesn't look like the capture shown here, press Command-Z [PC: Control-Z] to undo, then go back and check your Anchor grid setting to make sure you clicked on the left-center grid square).[View full size image]
Step Four
Now, open the second segment of your pano. Notice that part of the taxi on the far right of the first segment also appears on the left side of the second segment. That's absolutely necessary because now we have common objects that appear in both photos, and we can use the taxi as a target to align our panos.
Step Five
Press the letter V to get the Move tool from the Toolbox, and click-and-drag your second segment into the first segment's document window. Drag the second segment over until it overlaps the first segment a bit. If needed, zoom in so you can see the two segments overlapping.[View full size image]
Step Six
In the Layers palette, lower the Opacity of this second segment's layer to 50% so you can see through your top layer to the layer beneath it, which makes lining up the two taxis much easier. This is pretty much the secret of manually stitching panos. As the two taxis (your target objects) get closer in alignment, take your hand off the mouse and do the final aligning using the Left and Right Arrow keys on your keyboard. At first, the taxis will look blurry, but as the two target objects get closer to each other, the blur lessens.[View full size image]
Step Seven
If you're still having trouble lining things up, try this trick: raise the Opacity back to 100%, then change the layer blend mode of your top layer to Difference in the Layers palette. Now use the Arrow keys on your keyboard to align the taxi on the top layer with the one on the bottom. As long as you see color in the overlapping area (as you do here), it's not yet perfectly aligned.[View full size image]
Step Eight
Keep nudging with the Arrow keys until the overlapping area turns solid black. When it's black (meaning no colors are showing in the overlapping center area), it's perfectly aligned.[View full size image]
Step Nine
Go to the Layers palette and change your blend mode back to Normal (that is, if you set it to Difference, otherwise just raise the Opacity to 100%) to see how your stitch looks. The two images should look like one (that is, if you shot them using a tripod and didn't bump the camera along the way).[View full size image]
TIPIf you see a hard edge along the left-hand side of the top layer, press E to switch to the Eraser tool; choose a 200-pixel, soft-edged brush by clicking on the Brush thumbnail in the Options Bar; and lightly erase over the edge. Since the photos overlap, as you erase the edge, the top photo should blend seamlessly into the bottom photo.Step Ten
Now, open the third segment of your three-segment pano.
Step Eleven
Repeat the same technique of dragging this photo into your main pano, lowering the Opacity of this layer to 50%, and dragging the segment over your target object. (In this example, we're overlapping the van turning onto the street.)[View full size image]
Step Twelve
Don't forget, as you get close to aligning the vans, take your hand off the mouse and use the Arrow keys on your keyboard to align these last two segments. (Don't forget to try changing the layer blend mode to help you align the two segments.) Again, after you raise the Opacity of the top layer back to 100% (or change the blend mode back to Normal), if you see a hard edge between the two, use a soft-edged Eraser to erase away any seam.[View full size image]
Step Thirteen
Here the three segments are stitched together, but I overestimated how much canvas size we'd need, so there's some blank canvas space to the right of my pano. To quickly get rid of it, go under the Image menu and choose Trim to bring up the Trim dialog. The area we no longer need is on the right-hand side, so in the dialog, under Based On, choose Bottom Right Pixel Color, which will trim away everything outside your photo that is the color of your bottom-right pixel (which is white).[View full size image]
Step Fourteen
Click OK in the Trim dialog, and the excess canvas area is trimmed away, completing your pano. Now, this was an ideal situation: You shot the panos on a tripod, so the stitching was easy; and you didn't use a fisheye, so there wasn't much stretching or distorting to deal with.[View full size image]
