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In this tutorial, I'm going to show you an easy shortcut for Sky Replacement with Reflections Using Luminar 4

And best of all, there’s NO HAND-MASKING REQUIRED!

One of the coolest features in Skylum’s Luminar 4 program is the ability to do something they call “AI Sky Replacement” which simplifies the process of swapping out a boring or poorly exposed sky for a more interesting or better exposed one.

Using an artificial intelligence algorithm, Luminar 4 can completely and believably replace the sky in your image without you ever having to use selections, masking, or layers. It’s all fairly automatic.

And that’s the genius of this feature. It finds and masks off the sky areas automatically so you don’t have to spend hours in Photoshop with a brush and a magnifier painstakingly selecting the sky areas by hand and praying that you didn’t accidentally color outside the lines resulting in halos at the edges of your selections and a poorly blended replacement sky. As Skylum says in their advertising: “Results in seconds without manual editing!”

I’ll admit I was skeptical when the feature was first introduced. But I have to say after using it for some time now, I am more than a little impressed with how well it works on the majority of images that call for sky replacement.

The AI routine does a fantastic job of automatically masking the sky portions and allowing you to fill them with one of the built-in replacement skies that come with the program or even one of your own sky photos.

The key to successful sky replacement is making sure that it looks realistic, natural, and true to the original scene in terms of exposure, color, and detail. Differences in exposure and white balance between the original image and the new sky will make the composite image look fake to your viewers even if they can’t explain exactly why.

Fortunately, Luminar comes with some clever adjustments you can make in the Sky Replacement tool that give you the ability to modify the position, exposure, color temperature, and blur amount of the replaced sky so it blends in naturally with the existing image. There’s even a slider to “re-light” the original scene so it’s more harmonious with the replacement sky. Using these kinds of adjustments, I am able to more successfully match my new sky with my original scene in almost every case.

Which brings me to the reason for this little video…

One of my photography students recently asked me if Luminar can do sky replacement on a photo that has reflections in it (like on the surface of a lake or other body of water) and make it so that the reflections match the replaced sky and still look natural.

And I thought to myself “You know…that’s a darn good question!”

Because if you are going to convincingly replace a sky, you need to do it everywhere the sky appears in your image – including reflections.

A quick search on YouTube netted me a dozen or more tutorial videos from various authors and educators explaining how to accomplish this sort of thing in Luminar.

Every one of these tutorials suggested a nearly identical technique for solving the problem of matching the reflections to the replaced sky.

Unfortunately, every one of their solutions had a significant drawback to it which I will explain momentarily.

First, they all tell you to use Luminar to replace the sky as you normally would, but they also caution you that for their reflection technique to work, you can’t use one of the built-in skies. You have to use one of your own skies because you’ll need access to that sky file again for making the reflection later on. And it’s not easy to get at the ones that are built into the program.

Second, after using Luminar’s AI Sky Replacement, they have you create a new image layer on top of your base layer and to load it up with the same sky you had used before. This new image layer then gets flipped over vertically and positioned to be used as the reflection in your image.

Finally, (and here’s where they lose me completely)
In the last step of every one of these tutorials, they instruct you to use the layer masking brush on the reflection image layer to hand-mask the reflected sky into the lower half of the scene. Yep, you heard me right. They all want you to hand-paint the mask for the reflection.

And in every one of these videos you can watch the person doing the demo struggle to paint that mask evenly. They have to work hard to avoid leaving halos at the edges of their hand masked reflections. They are always painting and erasing and painting and erasing to get it just right. They frequently fast-forward over that tedious part of the process in their tutorials and skip to the reveal at the end where they show off their replacement sky with matching reflection.

Now the first thing I thought when I watched these videos is that the entire purpose of using a program like Luminar to replace a sky is to take advantage of that amazing AI Sky Replacement tool to do all of that difficult masking work for you. Why on earth would you want to manually mask-in by hand all that stuff for the reflection? You may as well do that in Photoshop if you are going to do it by hand.

So it seemed to me that all of these solutions were:
   a) way more work than most folks probably want to do, and 
   b) a complete waste of Luminar’s great AI Sky Replacement tool.

After scratching my head over this little problem for a few minutes and wondering why it had to be so hard, I came up with what I thought might be a relatively quick and simple solution. In fact it was so simple, I doubted myself at first. I wondered if there was something I was overlooking.

Surely, there’s some way we can make the AI Sky Replacement algorithm automatically find and mask the reflected area as well? I mean…There’s got to be a better way, right?!

And sure enough, after a couple of experiments, I managed to figure out a simple repeatable method to do exactly that without any sort of hand-masking. And best of all you can use either the built in skies that come with Luminar or you can use your own skies.

And when you see how the trick is done, you won’t believe how easy it is to do. It’s almost embarrassing how simple the solution to the problem actually is.

UPDATE 2020-10-15:

Sklyum has just announced they will be adding a reflection feature to the new version of AI Sky Replacement coming in the next version of Luminar!

UPDATE 2020-10-20:

The latest release of Adobe's flagship program Photoshop includes a Sky Replacementfeature driven by their "Sensei" AI system. This is no doubt, a response to a similar feature that Skylum includes with their editor Lunimar. Here's my initial reaction to their offering.

I'm going to cut right to the chase and tell you that in my initial tests, Luminar is noticeably better than Photoshop.

It does a better job masking and retaining fine details. And it offers more useful tweaks for adjusting the replacement sky and how it interacts with your existing image.

Right out of the box, with no adjustments, Luminar produces more natural results. In many cases no adjustments are necessary at all.

With Photoshop, I was only able to get decent results by adjusting the parameters a fair bit after choosing a replacement sky.

Skylum has a head start on this tool and have updated and improved their implementation over the last 18 months. Adobe is new to the game, so we will have to watch and see if they can improve their algorithm. Remember that "Select and Mask" wasn't so great at first and now it's phenomenal. I will try to be patient as they work on their version of Sky Replacement.

For now, I'm sticking with Luminar for that particular task

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