In short, by placing a panoramic at the correct coordinates and specifying field of view, elevation, tilt, etc. it becomes possible to fly in to the image and look around it in detail. I decided to upload my night (hdr) panorama of Zurich but it wouldn’t let me — it wasn’t big enough! The image has to be at least 50 mega-pixels to be accepted. My original met this requirement but, as you may recall, I’d had to cut the image in 1/2 both horizontally and vertically in order to load it in to the HDR processing program. I could, of course, simply scale the image up but that would be cheating. So, I went back to the originals to try some new techniques.
There are two paths to follow… (1) Merge the images into an HDR with Photoshop and then do the tone-mapping with EasyHDR. Since I’d be loading just one 32-bit TIFF image, hopefully it would stay within EasyHDRs memory limitations. (2) Do HDR processing on each stack of images first and stitch those together into a panorama. This requires that the same transformation be applied to each stack in exactly the same manner or else there will be seams in the final image.
1) Merge into HDR with Photoshop
By restoring all the saved, aligned images I had made during my previous attempt, I had a good starting point. I recreated the three panoramas using PTGui and then loaded them all into Photoshop using “File::Automate::Merge to HDR”. The tone-mapping in Photoshop CS2 is poor compared to other alternatives, so at this point I saved it as a 32-bit TIFF.
Unfortunately, in the end I was unable to load even an image with 1/2 resolution in to EasyHDR. Windows programs that don’t do some sort of tiling of data (like Photoshop does) are generally limited to 2GB of memory. On to the next method…
2) Generate Multiple HDR Images and Stitch Them
The latest version of EasyHDR has some nice new features over what I used just 8 months ago. The trick here seemed to be to avoid anything that was dependent on the local image. To this end, I turned off the local mapping “mask” (which I don’t like anyway because it produces halos) and leave the general tone-mapping parameters at 1.0. I also never adjusted the black/white clip points, leaving them at the far ends of the spectrum. This would hopefully result in identical mapping for all image stacks and by saving in 16-bit mode there would be sufficient detail for me to adjust the total range in post-processing.
Before stitching, apply any filters that apply to a given image stack — noise-reduction, for example. Also, it’s likely that a lot of third-party software will not be able to handle gigapixel size images. You’ll have to run that processing on each part before stitching.
Along with these changes, I switched the panorama generation to be “cylindrical” instead of “rectilinear” as Earth will do all the perspective alterations necessary. If you’re not familiar with the terms, the latter is the standard image that non-fisheye lenses will give you. It’s what the eye would see looking through a frame held in front of you. A cylindrical mapping, on the other hand, is what you would see if looked through a vertical slit held at arms length and then rotated your whole body, combining the all that is seen into a single image.
Here’s the final image… Click on it to browse it at full detail! It should appear in Google Earth sometime in the future. Look for it at 47.37593N, 8.54651E.