3 HDR Panoramas

Now for the ultimate challenge. We’re going to combine these two disciplines of HDR and panoramas into a final, fully realized HDR image. This will require a careful approach to making sure the files are processed correctly.

Full HDR Panorama: Magnuson Park

  1. The chosen location is a widespread empty field at Magnuson Park. This avoids problematic trees overhead, as well as the interruptions of cars, pedestrians, etc.
  2. I set up the tripod as normal, oriented toward the sun, and using the pano head with a fisheye lens.
  3. Use DSLR Controller to shoot brackets starting from 1/4000, f22, and ISO 100, going up 2 EVs per shot over 5 brackets, ending at 1/15 sec.
  4. For angles 2 and 4, orient the tripod to have the sun just out of shot to avoid lens flares. Angle 3 is 180 degrees opposite the sun.

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  1. Upon finishing the default angles, I return to the sun angle. I shoot two more sun shots, first with one ND 1.2 filter, then with a second ND 1.2 filter. The finished image is pure blackness, plus a tiny dot of sun!
  2. Don’t bother shooting other angles for these ND angles. Since everything is darkness, their equivalent can be created later by erasing the sun on duplicates.

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Upon import, we’ve got our organizational work cut out for us.

  1. Right click on the lowest double-ND bracket, create a virtual copy, and lower the exposure on this copy by -4 stops. This is rearranged to #1.
  2. Create virtual copies for image 1, 2, and 3, and rearrange these to be in spots 9, 10, and 11.
  3. Use the Spot Healing tool to erase the sun on spots 9, 10, and 11. Now it’s the equivalent of those exposure rotated.
  4. Create virtual copies of 9, 10, and 11, and shift these to be in positions 17/18/19, and 25/26/27.
  5. Fix the sun position with offset in Photoshop like we did before.
  6. Export 1 through 8 renamed as angle1_1.tiff through angle 1_8.tiff. Repeat with 9 through 16 as angle2, and so on with the 3rd and 4th angle.
  7. Use ExifToolGUI to edit the EXIF exposure time metadata as before. Exposures 3, 2, and 1, all listed as their recorded 1/4000 exposure, are -4, -8, and -12 exposure stops from there. When you do the exposure math, you get: 1/64000, 1/1024000, and a whopping 1/16384000!

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HDR panorama creation must choose one of three methods: merging brackets first and stitching the outputs, stitching each bracket individually and then merging them, or doing it all at one time. In our case, we will first use Photoshop to make our finished EXRs, then stitch the EXRs together.

  1. In Photoshop, use File > Automate > Merge to HDR Pro. Select your first angle’s brackets. Note on import how the modified EXIF data successfully interprets the ND-affected and manually underexposed brackets as lower EVs than the 1/4000 exposure. Use 32 Bits.
  2. Save as an EXR. Repeat for the other 3 angles.

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Next, we need to stitch these angles together.

  1. Load the 4 EXRs into Hugin. Set the lens info, then crop and align as we did before.
  2. Based on experiments, I know the final output will be very dark, since it’s striking for the middle and we’ve included the sun’s full range. To compensate, select all the images, right-click, choose Edit Image Variables, then on the Photometrics tab, I set the exposure to 6.
  3. Export a final 4096×2048 high dynamic range EXR.
  4. Use Photoshop to fill in the blank areas of the finished output, clean out the tripod with stamping and content aware fill, and use Offset to both clean up the side seams and center the sun.

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So we’ve got a finished panorama. What’s the big deal? Why bother with all that format mess when the earlier methods worked? The reason is because the saved EXR truly stores lighting data inside the file. Now it’s ready for use in 3D applications, and the total light in the scene is actually captures successfully enough that objects can cast shadows, reflect highlights, and be reprocessed with 3D exposure settings as if the objects were right there in the Magnuson Park field. The 3D scene below has no other light objects except the HDRI. Of course, using Blender is a another tutorial entirely!

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Second Cool Thing

Fully realized HDR panoramas, suitable for use in a 3D production, is a very specialized subset of photography. As a result, the tools are often so esoteric that we are left with a choice of spending extra for special software, or suffering the consequences of their inadequacies in both HDR merging and panoramic stitching. This next HDR panorama shows an alternative software pipeline with more desirable results.

 

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HDR Panoramas Copyright © 2021 by Oscar Baechler is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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