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Sky replacement round two: LuminarAI vs. Photoshop

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One of the most anticipated features lately in both Luminar and Photoshop are their AI-powered sky replacement tools. Many of us night photographers would love to blend hour “blue hour” photos with photos of the night sky taken later in the same camera position. This can be time-consuming. Which can quicken the process more?

Skylum LuminarAI SkyAI vs. Adobe Photoshop Sky Replacement

I decided to take a look at the most recent version of LuminarAI‘s SkyAI — which is receiving an update this month — with the most recent version of Photoshop 2021. I used a day photo with complex pine needles. Such fine details provides a challenge for sky replacement programs.

I also decided not to go through a detailed, step-by-step process. The idea here is to see what one could do right away using minimal fussing to provide an apples-to-apples comparison.

LuminarAI SkyAI

I loaded the photo of a Mt. Pinos photo, above.

I loaded the photo of a Mt. Pinos photo, above.

Above is the appearance after loading my custom sky and then the Vertical Offset slider to adjust the sky.

Above, I adjusted the brightness to help blend the sky with the foreground a little more. I then adjusted several sliders in Mask Refinement. I was able to fit the stars around the horizon, including the pine needles and branches of the trees, by adjusting these parameters.

Above is a zoomed in view of the of the horizon. I zoomed in at 220%. This is of course pixel peeping. No one would ever view your final version like this. However, it’s educational for us to see what is happening.

Adobe Photoshop Sky Replacement

I began with the same photo again. Above, I’ve actually already loaded in the replacement sky, but have it turned off to show the initial photo.

Above, I have loaded in my custom sky. This is how it appears after adjusting the position of the sky. This is easily done with the Move tool on the upper left column.

I noticed that there was a lighter halo around the horizon, including the trees. I adjusted some of this by painting on the Foreground Lighting Layer Mask, located on the lower right of the screenshot above. I then zoomed in to the same area as the LuminarAI image. Like before, I zoomed in at 220% for educational purposes.


I immediately saw four noticeable differences:

  1. There is a curious color difference. Adobe has changed the color of the sky from the original night sky. This can easily be addressed. Photoshop is, after all, a powerful program. However, it’s curious that it ever occurred.
  2. The details in the trees, notably in the trees on the mountain, are preserved better in LuminarAI.
  3. The top of the foreground is darker in Adobe than it is in LuminarAI.
  4. Despite me addressing the lighter blue halo around the horizon and trees, it’s still noticeable. I could have taken more than time and removed the halo. However, the fact remains that there is still a halo there, but none with LuminarAI.

See if you can find other differences. The stars might off slightly from one to the other because I was “eyeballing” their relative positions. Try to see if you can see differences in the quality of the blend and any artifacts.

What else puts LuminarAI ahead? Reflections

In addition to the adjustments Skylum has made to SkyAI that I mentioned above, there’s one much-anticipated feature that puts it over the edge — reflections. You can now swap out the sky and have it reflect in the water below. I used a photo below, by Bryan Esler, to illustrate this.

I spent approximately two minutes with each sky replacement program. I wanted to do this to make the comparison reasonably fair.

This is an updated version of LuminarAI, set to be released on March 16. I was able to get an early look at it for this article. The sky replacement is noticeably better than the previous version. I have no doubt that Adobe will continue to develop their sky replacement tool. The advantage that Adobe has is considerably more options and power in tweaking the initial sky replacement. I like options and power.

However, it is also in contrast to Skylum’s philosophy of having AI do more and more of the heavy lifting and decision-making for you so you spend less time in post-processing. For now, in early March 2021, LuminarAI seems more effective and appealing for my workflow. However, the battle will go on, and in the end, we the consumers are the winners.

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Ken Lee

Ken Lee

I am a night photographer. I drive long hours in a dusty car listening to weird music, stay out all night creating photos, get dirty, hang out with other creative sleep-deprived weirdos, see the stars drift across the sky and always find the best taco stands while photographing forgotten abandoned locales and amazing nightscapes. I have one book published with two more on the way, and my images have appeared in National Geographic Books, Omni magazine, Los Angeles Times, Westways magazine and numerous other publications.

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