Litchi is able to automatically create a 360-degree panorama by stitching together a series of photos and then displaying that 360-degree panorama within the Litchi app (IOS Only). However, there are a number of reasons why one may wish to process the series of images manually. These reasons include:
- To improve the stitching quality
- To perform color grading of the sky and foreground
- To display and share the 360-degree panorama in Google Photos
The above steps can be complicated and difficult to perform. This guide will provide some guidance to performing those steps with an emphasis on getting the 360-panorama to be properly recognized and displayed as a panorama in Google Photos.
Improve the stitching quality
Litchi’s image stitcher works quite well. However, sometimes the stitching produces unacceptable results. For example, the following panorama of Bear Butte in South Dakota had an unfortunate seam passing right through Bear Butte.
To correct this, it might be necessary to use another stitching program. A few are available. I use Microsoft’s Image Composite Editor (ICE). Stitching the individual images in ICE produced superior results.
Perform separate sky and foreground color-grading
Depending on the lighting conditions, a panorama might include a very bright sky with a relatively dark foreground. For example, the following photo of the open-pit mine in Lead, SD combines a light sky with a dark ground.
To correct this, it may be necessary to perform some image work using Photoshop or similar. I duplicate an image like this into two layers then adjust one for optimum sky and the other for optimum foreground. Then, I combine the two with a smooth blend across the horizon.
Prepare the image for display in Google Photos
This last step can be the trickiest part. Some photo display applications like Google Photos will automatically detect and display 360-degree panoramic images using an interactive panoramic viewer. However, Google does not make it clear at all how it automatically detects a 360-degree panorama. The question of how to make Google Photos detect and properly display a 360 pano has been asked hundreds of times in Google’s support, but never with an acceptable answer. Google’s responses are always along the lines of “try clearing your cache”, “try a different browser”, “try the app”, or “try a different computer”. Clearly, Google’s support people have no idea how their own software works.
Here are the steps required to make Google Photos automatically recognize and properly display a 360-degree panorama.
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The aspect ratio of the image is important. A 360-degree panoramic must be twice as wide as it is high. For example, if the image is 2000 pixels wide, it must be 1000 pixels high. If the image aspect ratio is not 2:1, it will not display as a panoramic image in Google Photos. After stitching the images, the result must be brought into an editing program (I use Photoshop) and the canvas size must be made 2:1 by adding some sky. I normally copy the entire width of the sky and then flip vertically and stretch to fit. One can spend more time blending the flipped sky with the existing sky but this step is not entirely necessary when viewing the image as a 360-degree pano. The details of how to do so are beyond the scope of this tutorial.
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Google Photos has an upper limit on the size (in pixels) of images uploaded to their site. This limit is 100MP. Don’t confuse this with the image size on disk (this is mega-PIXELS, not mega-BYTES). This is simply the number of pixels in the X-direction multiplied by the number of pixels in the Y-direction. To get the optimum size, we know that x * y <= 100. We also know that x = 2 * y. Solving for Y yields 7000. Therefore, the optimum size for a 360-degree panorama uploaded to Google Photos is 14000x7000. This will be a 98MP image. If necessary, scale the down to 14000x7000.
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Google requires that the EXIF data contained within the image properly specifies that the image is a panorama. To edit the EXIF data within the image, one must use an EXIF data editor. A few are available such as EXIFTool (for advanced users) or “EXIF Pilot”. I use “EXIF Pilot” to set the EXIF/XMP data as shown in the image below.
Once the above steps have been completed, the 360-degree panoramic image may be uploaded to Google Photos where it will be properly detected as a 360-degree panorama and displayed accordingly. Here is a 360-degree panoramic photo (displayed as a flat image) that has gone through the steps outlined above. Notice that Google Photos placed a circular arrow in the upper-right corner of the image indicating that it has been detected as a 360-degree pano and will be displayed properly if selected.
I hope this saves someone some time. It took me a while to research this and figure out all of the details to make this work.