Multilevel indoor shopping malls provide good subject matter for spliced panoramas that use four images in a 2 × 2 array. Activities on the levels provide a doll house effect, with many small “rooms” in the scene to view. I took these four images in front of Macy’s at the Newpark Mall in Newark, California recently:

Theoretically, the Photomerge™ option in Photoshop™ should put the four images together into one seamless image. I tried that, but it didn’t work. The problem is that there are four different perspectives to be merged into one image, and each image overlaps all three of its neighbors. It wouldn’t be a problem if Photoshop had an option for a spherical projection, but it does not. The cylindrical projection only works for horizontal stitching, so we are left trying to piece together flat images into a faceted composite.

The best strategy is to first merge two images vertically to make half of the final image. Here I chose the two left Images.

The stitched half must be flattened and then cropped. There cannot be white margin on the right edge, so Photomerge can stitch to that edge. I then added the two images on the right and let Photoshop complete the stitching. That worked in this case, but sometime it helps to stitch the right half first and then combine the left and right halves. After stitching, I used Correct Camera Distortion and rotation to try to get the image to look as normal as possible. There are really four different perspectives in the image, so it is a compromise. Notice that the wreath appears to be swaying to the right, and the Christmas tree on the first floor is stretched.

I allowed a fair amount of overlap among the images to facilitate stitching, and I hoped to crop out any person who walked from one image to another as I took the sequence. The Mall had few shoppers at the time, so I was lucky and did not have to do that.

There are other problems. The red banner at upper left did not stitch seamlessly. The right edge of the banner is aligned, but there is a discontinuity in the left edge. this could be touched up by copying a piece of the edge and pasting in to gradually move the line over. That is work to be left to a colder winter night.

Many panoramic images have too much detail to see well on a small reproduction of the image. Even with substantial overlap of the four component images, the final mall image has over 25 megapixels. Here is a detail from the image showing the actual pixels. The detail is from just above the railing near the right edge of the image.

It would take a fairly large print to show the detail well. At 300 pixels per inch, the print would be about 16 × 20 inches [40 × 50 cm]. At that size the stitching glitch would be easily noticed. Besides, who wants a large print of a shopping mall? Well, maybe if there were a real bargain on machine prints …