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Anatomy of a Nightscape, Episode III: HDR and Focus Stacking

I’ve described at length many of the techniques I use to shoot nightscapes. In this tutorial series, I’d like to keep things much shorter and pick apart some of my photos with minimal step-by-step instructions. The shot we’ll be going over this time was taken in the Pecos Wilderness of north-central New Mexico.

Gear

Camera: Canon EOS 6D
Lens: Canon EF 35mm F/1.4L
Tripod: Manfrotto 190X with Ball Head
Tracker: None
Other: Remote shutter trigger via Android phone

Software

Planning: SkySafari 5 Protimeanddate.com
Shooting: DSLRController (remote shutter control app)
Editing: GIMP 2.10.4, Adobe Lightroom 6, Enfuse

Location

Pecos Wilderness, New Mexico, but not in a place you might consider “scenic”. I wanted to try to get a shot of the sky with some flowers in the foreground, and wouldn’t you know that the best-looking flowers happened to be just outside the campground outhouse!

Top Left: The outhouse where I shot the picture from. Mid Left: The flowers near the sign were best-positioned for the planned shot. The moon would set to their right. Bottom Left: The rock marks the spot where I set up. Right: The view from that spot during the daytime.

 I had actually wanted to shoot this the night before when the moon and Mars were a little closer to each other, but we got rained out that night, most of the next day, and for several more hours again before things cleared up and I could finally take the shot at 4AM. All the water droplets in the grass made for some nice pinpricks of light in the scene’s foreground.

Step-by-Step

  1. Set up camera and tripod, center moon in the frame.
  2. Expose for the moon’s face. (F/2.8, ISO800, 1/4000th sec)
  3. Expose the sky, opening the aperture all the way to avoid diffraction spikes on the moon, Mars, and stars.
    It’s important to shoot these first because the sky will move out of your composition more quickly than you might think. (F/1.4, ISO800, 8 seconds + 15 seconds)
  4. Expose a focus stack of the foreground. The closest objects in the scene were only a few feet from the camera while the farthest objects (ridgeline, sky) were several miles to many miles away, so this required 5 shots with the lens stopped down. Start with the closest subjects in focus and work your way out to the farthest ones. (F/5.6, ISO800, 15 seconds each)
  5. Back at home, convert RAW images to TIFF and open all in GIMP.
  6. Manually align sky shots and focus stack. Your focus stack will more than likely show some focus breathing, a slight change in the lens’ focal length as the focus changes, hence the need for manual alignment. After alignment, crop down all of your layers to the same extent.
  7. Export all of your layers as new TIFF images.
  8. Use Enfuse to produce a focus stack of your foreground shots.
    – Set exposure and saturation weight to 0 and contrast weight to 1.
    – Set contrast window size to 5 pixels.
  9. Reload your aligned sky shots and focus stacked foreground image into a new GIMP image.
  10. Enhance star color and size. To do this:
    – Duplicate stars layer.
    – In new stars layer, use Magic Wand tool to select the sky background. Add foreground portions to selection and turn the entire selection 100% transparent.
    – Use a 1.5 pixel gaussian blur over the entire stars layer.
    – Increase color saturation of blurred stars layer by 100%. You may also want to increase the overall brightness of the layer.
    – Merge stars layer back onto sky layer using Color blending mode.
  11. Merge all layers.
  12. Use spot healing tool as necessary to remove stacking/fusing artifacts.
  13. Export to TIFF.
  14. Enhance overall color saturation/sharpness in Lightroom as desired.

Final Thoughts

Silly location aside, this was a difficult image to process. Ultimately, it was composed of 8 images with three different apertures and exposure times. It took about 4 hours of editing time to get the image to look the way I wanted it to. Being 100% honest, I’d like it if the moon were a bit larger in the frame but I can’t bring myself to edit in a different moon image. To me, that feels a little … dishonest (but that’s just me). So next time, I may try this with a lens in the 70-85mm focal length range.

What are your thoughts? Drop me a line in the comments below!

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