How Panoramas Are Made

Comments or questions: henry@cs.niu.edu

Update 09/06/08: Most of the information below is still basically correct, but I now use Photoshop CS3's Photomerge function to do the stitching of panoramas.  It is fundamentally automatic and almost always works perfectly (no "ghost" images, no mismatched borders).

Note: also see James Riggs site http://www.panoguide.com for a lot more information on panoramas, including a good explanation of parallax and stitching software reviews.

Most of the seamless panoramas were made as follows:

1. Take 2 to many pictures with a 35mm camera - or digital camera. 

• Use the same exposure for each picture (set the camera to the best guess of average illumination over the scene).  Some people claim you can vary the exposure by a stop or so among all the pictures (to better expose dark or light areas of the panorama).   I find that stitching programs have trouble blending colors (especially sky areas) if they do not have the same exposure, and it's hard to fix this in an image editor. So from my experience I would avoid altering exposure.
• Overlap the pictures by about 20% for normal focal lengths (50 mm and up).  The wider the lens you use, the more you should overlap - up to 40% or 50% for a 20 mm lens.
• Hold the camera level.  Tipping it up or down will cause the final combined result to be curved into a "smile" or "frown".  This may take some practice to do well.  Some stitching software (such as Panavue's ImageAssembler; www.panavue.com) can compensate for this, so if you want a lot of sky or foreground, this is possible.  Generally you will want level and horizontal, though. A tripod can work, especially if it has a useable bubble level.   I've found that hand-holding works ok most of the time if you're careful. 
• The pictures can be portrait or landscape orientation. 
• If you use a good stitching program like Panavue's Image Assembler you can use almost any lenses.  Even a 20 mm lens is workable with Image Assembler, despite the distortion at the edges.  IA warps the images to (usually) produce a seamless and perfect panorama.
• If your panorama includes distinct objects in the foreground, you may have trouble with parallax.  As you pivot holding the camera, the point of view changes and the foreground shifts with respect to the background in the overlapping parts of adjacent images.  The stitching software may not be able to handle this.  You can try to eliminate the problem by attempting to eliminate parallax by sight (hard), eliminating the distinct foreground element, or using a tripod with a special mount to pivot the camera on its optical axis. Riggs (link above) discusses this.  In practice, for the pictures I take, this has not often been a big problem - but for certain images with distinct foreground and background objects, it can be.

2. (Film only) Scan the negatives with a film scanner (I use a Polaroid SprintScan Plus).  

• If the final product is to be printed, scan the slides at a resolution so they can print well.  For example, scanning one picture at 1350 dpi will produce a scan of about 2000 by 1300 for a horizontally oriented 35mm negative.  (Recall that a 35mm negative is about 1" x 1.5").  So then if you print at 240 dpi (typical for inkjet printers), the picture will be 5.4 inches high.  Length, of course will depend on how many pictures are combined. 
• If the final product is just for the Web, use a much lower setting (try 100 dpi).   If you want to print and post to the Web, scan and save at the print setting (so you can print) and then reduce the size (and resave with a different name or in a different place) before posting to the Web.  (See below.)
• The scanning settings for each picture should be the same (just like the exposure for each picture in step 1 should be the same) so that the stitching software can blend the colors and brightnesses easily.  If you let the scanner autodetect brightness, color balance, etc, it will optimize each picture independently and they won't merge well.

If you don't have access to a film scanner, you could

• have your pictures put on a Photo CD.
• scan prints on a flatbed scanner.  If you do this, have the photos printed at a place where they agree to use the same print settings for all the pictures in a series.   Maybe not Jewel or Wal-Mart, but your local camera/photo store where they do the work there and you can talk to the person who does the work.
• use a flatbed scanner slide adapter (a little mirror thingum).  Quality won't be so good, but it is probably acceptable if you don't want to make the prints too big.

3. Use "stitching software" to combine the images.  I now use Panavue's Image Assembler almost exclusively.  The resulting file can be quite large - often 30 to 90 megabytes depending on the number of pictures and the scanning resolution, so you need a fairly powerful computer with lots of RAM.  128 Meg is barely adequate for the largest  of these images.  There are many such software products on the market (see Rigg's reviews for features and price).  Save the resulting image in an uncompressed (lossless) format such as .bmp.

4. Open the stitched image in a good image editing program (I use Adobe Photoshop) for cropping, dust removal, color adjustment, sharpening, etc.  If the resulting picture is to be saved for later use or additional editing, it should be saved using a lossless compression mode such as .bmp or .tiff.

5. Printing is best done on a good inkjet printer that can print on long narrow paper.   I use an Epson R2400 (and previously an Epson 1280 and 1200 and before that an EX).  You will have to buy roll paper and probably cut it to the size you want.  Instructions on this will vary according to the software and printer you use.

6. To save a panorama for Web, you should reduce the size so that it will display on-screen at a reasonable size. Screens are about 72 dpi. In Photoshop, this is done using Image/Adjust/ImageSize, with Resample checked. Other image editors have similar features with different names.  Remember that a typical Web browser takes up space at the top and bottom of the screen.  If you assume that a typical screen has a 800 by 600 resolution, you maybe have 400 or a bit more of open vertical space for your picture. Of course, the panorama will then be wider than the screen, so the user will need to scroll horizontally.  The altered image than should be Saved As a .jpg image (a greatly compressed version that nevertheless looks good.)  Be careful not to just Save after you make your size changes or you will lose the original.  After saving as a .jpg, your panorama is now probably about 150K (down from the original 50 Meg).  This will take a minute or so to load over a modem connection, so you should put just one such image on a Web page.  Software such as Microsoft's FrontPage or Adobe Photoshop will help you make a thumbnail-based table of contents.

That's it.

Note on print width under Windows: David Lutz  (dlutz52@yahoo.com)   emailed me as follows:

I have on my wall a panorama that is 97" in length printed on 13" roll paper with an Epson 1280. I run Windows 2000 SP2, Photoshop 6.0.1 and use version 5.2 of the Epson printer driver. Neither Photoshop nor Illustrator where able to handle the printing of this 72 dpi image - although Photoshop is the program I used for stitching and color correx. After the failed printing, I fell back on the image editing program I started with long ago - Jasc's Paint Shop Pro 6. After fiddling around with the settings between PSP6 and the Epson Setup dialog, I got my panorama printed. It took over an hour to print (using the High Quality setting rather than the High Speed setting) and used over 1/2 of a cartridge of color ink. In fact, the cartridge was empty at the end of printing. The image is not edge-to-edge (in 13" direction) even with No Margins option selected. The instructions with roll paper state that there is a 3mm border on top and bottom edges of roll. This is what I found to be true - regardless of what I have read in reviews. As this was not the major focus of my effort here, I cannot attest to the quality of the color of the print - except that the color of the printed image was satisfactory to me. Quickly, my steps were: