|"Producing Polar Panoramas"
Tutorial and pictures by Jeremy Birn
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This tutorial describes a fun and challenging project for intermediate to advanced Photoshop users, and is not for beginners. Some of the steps below require the creative use of your own Photoshop skills.
The steps below show how a Polar Panorama is created. A Polar Panorama can make a 360° view appear to be a separate planet as shown below, or could be created with the sky as the center of the image as shown at the bottom of this page. A Polar Panorama makes a terrific print at any standard dimensions, and avoids the problem of printing and framing long, thin panoramas.
This image started with a set of 16 separate shots I photographed with my Sony DSC-F707 digital camera:
1. Mounting the camera on a tripod would be the best way to shoot these pictures, but I was traveling without a tripod, so I just held the camera as level as possible, and turned around, shooting 16 pictures that covered the scene all the way around me. I gave about 25% overlap between pictures so that, as you can see in the thumbnails above, the right edge of each shot shows the same area as the left side of the next shot, making it possible to seamlessly stitch them together. Your own pictures may vary, but it's best to get a full 360° view.
2. Using Panaview Image Assembler, I assembled the 16 pictures into one continuous linear panorama. If I had used a tripod the results probably could have been straighter and more uniform. (Note: If you don't have any panorama stitching software, I recommend visiting www.panoguide.com for reviews and links to the different programs. Some of the companies offer free trial copies.)
3. Using Panaview Image Assembler again, I wrapped the left edge together with the right edge to make them seamless and bring the two sides into alignment. This cropped the image, but then in Adobe Photoshop I cropped it some more and cleaned up some imperfections.
Some people stop here and make this kind of panorama as their final product, although the long thin shape makes them hard to print and display. Because the left and right edges will seamlessly connect together, printing large images like this on translucent material would make a nice lampshade, although I haven't seen anyone manufacturing those yet. To create a perspective that can be printed as an ordinary photo print with dimensions such as 8" x 10" or 11" x 17", you'd want to wrap the 360° view back into a circle.
NOTE: An alternative to steps 4 though 7 below is available if you use any 3D rendering software - try using the panorama as a texture map wrapped around half of a sphere, and rendering an orthogonal perspective on it. Your different texture mapping controls and rendering options will allow for more adjustment over the perspective than you could achieve by finishing the project in Photoshop.
4. Because the seamless image I started with was over 18,000 pixels across, I made a new copy scaled down to 1000 pixels in width. If you scale your image smaller you can experiment with steps 5 through 7 until you are happy, without wasting too much time processing a very high resolution image.
5. In Photoshop, flip the image upside down, if you want to produce a ground-centered panorama.
6. Increased the Canvas Size around the image to make it a perfect square, leaving most of the canvas below the image empty. The next figure shows some guidelines for how to prepare your image:
7. Chose the Photoshop function Filter - Distort - Polar Coordinates, and use the Rectangular to Polar option to wrap the image into a polar panorama.
8. You may want to undo your initial results and experiment with changing the position of your original image within the canvas, or with scaling the image up in height, and then redo step 7 until you are happy. If you are working with a scaled-down original image, then eventually you will want to go back and repeat the process with a higher resolution image. Remember that you only need the original to be about twice as wide as it is high in order to get consistent resolution.
NOTE: An alternative to Photoshop's Convert Polar Coordinates is the much more versatile Flexify plug-in from Flaming Pear. Flexify doesn't crash as often when wrapping larger files, has better anti-aliasing, and has far more features for creating other kinds of projections. It does sometimes create glitches such as a grey bar a few pixels high cutting across your output, but this has been retouchable and it could be worth the $20 if you want to make a very high resolution Polar Panorama.
9. If you left any space at the top of the image before using Polar Coordinates, then you will have a hole in the center, as shown above. Cut and paste lassoed areas of the image to fill in the hole, or use the cloning tool to duplicate other parts of the ground. If you want to get fancy, you could shoot a separate picture of the ground and composite it into the hole at this stage.
10. Clone the sky outwards to fill the rest of the canvas, or just crop the canvas into a smaller rectangle to frame the area in the center of your polar panorama. More creative manipulations with functions like Filter - Distort - Spherize could help improve the proportions on some shots. The final product can look like the image as the top of this page.
As an alternative, if you don't want the ground to be in the center of your panorama, then you don't need to flip the image upside down in step 5. The result can look like the image below, with the sky in the center of the image:
Either way, wrapping your panoramas in a polar or spherical projection can make for more interesting panoramic photographs to print and display.
Polar panoramas and all contents of this page Copyright © 2001-2006 by Jeremy Birn. Please do not copy without prior written permission. "Make Links - Not Copies!"