Milky Way and Palm Trees

Star Shaping

In this video I work on enhancing the Milky Way without having the stars around it get too bright. I introduce a method of star shaping which gives results a little like the color reconstruction module. The processing involves lowpass filters applied with the darken blend method to produce stars with a spherical appearance. As is common for me, you will find considerable use of parametric masks in this edit.

If you'd like to follow along in this edit, here's the original RAW file

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Hi everybody.

This is Harry with another Darktable screencast.

This time I'm working on a night shot.

It has the Milky Way.

It's got trees that are very dark.

I want to separate the Milky Way from the sky.

I don't want to over-expose these stars.

A lot of them are already over-exposed.

This is a 30-second exposure at F2, at ISO 1600, so a lot of these stars, the middles of them are gone.

They're just burned out.

And there's some color around the edge.

Okay, so I don't want to make that situation worse, but I do want to see some separation between the Milky Way and the center of the Milky Way.

These trees are so dark, I'm going to deal with them in three stages.

The first thing I'll do is lighten them up, get as much information as I can, and then the second thing I'll do is deal with the noise in the trees.

There's going to be a lot of it.

Then, the third thing I'll do is try and add some tonality and detail back to the trees after I've Denoised them.

So, first thing we're going to do here is look at Hot Pixels.

When I look at an image that's 30 seconds long, I usually see about a thousand hot pixels.

If I turn on the Hot Pixel Module, I see that it found 96.

I'll add the Detect by 3 Neighbors Option and it came up to 730.

That seems like it's about fine, so I'm not going to bother with any of the other settings.

Next thing I'm going to work on is the De-Mosaic Algorithm.

My default method is PPG, but with stars, I feel like I get better results with Amaze.

Let's look.

We'll take a Snapshot of the screen here.

On the left will be PPG, and then on the right, we'll use Amaze.

For instance, look at this star right here.

It's white, and then it abruptly goes to a darker color.

That's under PPG.

With Amaze, we get much more smooth transitions.

You can see that's true with most of the stars: better results with Amaze.

Better yet by turning on Color Smoothing and running it twice.

I'm even happier with those results.

I don't like to run the Color Smoothing five times because I find it gets soft.

Likewise, with the VNG4 Demoisaic-ing Algorithm, I find the results are soft First two things: we have Hot Pixels and Demosaic-ing.

The next thing we want to look at is Chromatic Aberrations.

The nice thing about that is it does a lot of work for you.

All you have to do is turn it on.

Here it is before.

I'll take a Snapshot.

It gets rid of a lot of the color noise in the sky, and it also helps with a lot of the fringing on the stars.

On the right hand side is with it, and on the left hand side is without it.

That is good.

Alright, the next thing I'm going to work on is the fact that it's dark in the corners.

That's probably because it's going through more glass.

I am going to use the Vignet some, but I'm going to use it with positive values for Brightness.

I'm going to bring the Vertical Center all the way down and increase the size, fall off Strength, bring the edge there, and then turn my Brightness and my Saturation to zero, and then increase them until they look right.

Oh, that looks good.

And, more Saturation.

There we go.

Next thing I've got is Tone Mapping.

Now, that's to bring out the detail, whatever details I can find in these trees.

I like to start with about 6% for my Spatial Extent and I'll set my Compression at 1 to get started here.

I only want to select the trees, not the sky, so I'm going to use a Parametric Mask and use the L Channel to separate the trees from the sky.

I'll turn on the Mask Indicator and then turn down the upper limit of my L Channel to isolate just the trees here.

There we go.

I've got a bunch of stars too, so I'm going to use a Drawn Mask combined with the Parametric Mask and paint in where the trees are.

I'm going to take this and turn it down to 1.

There we go.

And now, I'm going to turn up the Compression, see if I can get any more.

Well, there we go: 1.6; I don't think I can push it any further than that.

Alright, what else do I have? I'm going to use this Lowpass Filter.

These black spots are just where the stars were exceptionally bright.

Ignore that; they won't do anything.

I'm going to use this Lowpass Filter to make the trees a little bit lighter and the sky a little bit darker.

I'm going to increase the Radius so that I'm not including any details, just the more macroscopic sized objects, and then I'm going to take my Blend Mode and change it to Overlay.

Then take my Contrast and bring it all the way down to zero, and then I'm going to start going negative with it.

This should look the same as the original.

Yes, see: there's no difference.

Now, if I take my contrast and go negative with it, my trees get a little bit brighter, my sky gets a little bit darker, and that's about as far as I want to go: -0.28 negative.

One other thing I want to deal with is I get this purple fringing with this particular lens.

It must be one of the coatings.

I can specifically look for this color purple and reduce it.

The best tool for that is this Color Zones.

Use the Eyedropper.

Change the method to Area instead of Point and then select this purple here.

See, it's right here, but I don't want to pull down on this Control Point.

I want to put Control Points on either side of it so I can pull down on a very narrow band.

If I use the Mouse Scroll Wheel, I can make the selection size smaller, and that gives me more control over which colors get de-saturated.

There we go.

Okay, that's the first phase.

I'm going to save this as a 32-bit float.

Size is zero and zero.

I stay in Adobe RGB.

The reason I save between different stages is because I use Parametric Masks to adjust what my imports are, and I want the Parametric Mask to know what values are coming in.

If I change my Tones, then I can change a Parametric Mask of a Module that I use later on, so I do Saves in between and then I know exactly what I'm getting.

In this stage, I want to enhance the color and shape of the Milky Way.

I'll be doing that with the Equalizer.

I want to deal with the noise in the trees because when I made them brighter, I also ended up with a lot of noise.

First thing: the Milky Way.

I want to use the Equalizer Tool, but I don't want it to apply to the trees, just the Milky Way.

I'm going to use the Parametric Mask again, and this time isolate the trees from the selection area.

Oops, too far.

Okay, I think that's about as good as I can do.

Now, if I raise these different Control Points, we can see what sizes the Local Contrast will be enhanced.

These are the largest sizes, on the left.

Before, and after.

Okay, and the next size down.

And the next size down.

Alright, so for the Milky Way, I pretty much want these two larger sizes.

Before, and after.

That looks right.

I also want to do the same thing, but with Color.

Now, the Color I can bring up a lot further than I can the Contrast.

There we go.

Before, and after.

Looks good.

Now, I said I want to work on the noise in the trees.

So, let's get into these trees and see what we can do.

Now, I'm going to select just the trees, so I'm going to use Parametric Mask again, once again using the L Channel to separate the trees from the rest of the image.

I should zoom out, turn on my Mask Indicator.

Okay, we just want the trees.

Once again, I'm going to combine it with a Drawn Mask.

I'll just get rid of the areas I don't want to include, and reverse the Polarity of the Mask.

Turn off my Indicator.

Alright: Noise Reduction.

Well, this is too far.

This is at 10 pixels, so let's bring it down a little bit.

How far can I bring it down before I start introducing noise? Oh, boy; there it is again.

Right about there is about as far as I can go.

Radius 3.8 Alright, well; that smoothed it out a lot.

Much better.

I'm going to lower the Opacity of that just a little bit to get a little better shading in here.

Then I'm going to Save again.

This time I'm going to bring out some of the detail in the trees, and I'm going to richen up the colors in the sky with two different techniques.

One of them involves using the Subtract Blend Mode, and the other one involves using the Multiply Blend Mode.

First thing: trees.

Bring out more detail in the trees.

Once again, I'm going to use the Parametric Mask to isolate the trees.

I'm going to bring out the details with the Highpass Filter.

I'm going to use the Sharpness and the Contrast Boost to bring up details in the trees.

See these splines and these branch nodes and the trunk? Some of these leaves...

Then, I'm going to add that in with the Soft Light Filter, and it makes too much.

See, this is too contrasty now, so I'm going to turn it down considerably.

That's without it, and then I'll bring it up, right about to there looks good.

Maybe a little bit lower: around 55%.

Now, it's working on the sky too, and I don't want it to work on the sky.

So I'm going to change this to Parametric Mask and then turn on my Mask Indicator and have it just work on the trees.

Before, and after.

See how you can see the middle of the branches better, and you get more 3-dimensionality.

This is before, and after.

That looks like what I'm looking for.

Now, I mentioned two methods of enriching the colors.

The first is the Subtract; the second one is a Multiply.

The first thing I'm going to do, though, is try and lighten this image a little bit.

I want to concentrate on the branches and the trunk of the palm trees, so I'm going to use the Tone Curve and then sample this area here.

Find out where it is, and raise that a little bit.

Now, I don't want the sky to be so bright, so I'm going to bring it down a little bit.

I'd like for the MIlky Way to be brighter, so I'm going to bring it up a little bit.

There we go.

Before, and after.

Next thing I'm going to do: Subtract.

The way I do this is I use a 3-pixel Radius.

I leave my Contrast and Saturation the same, and then I'm going to Subtract this from the underlying image with Blend Mode of Subtract.

Now, this is going to make everything really dark.

I'm going to take this and apply it very lightly.

There's 7%.

There's 9%.

9% looks pretty good.

Now, I don't want it to work on the palm trees again, so once again I'm going to use the Parametric Mask and exclude the palm trees from the image.

Alright, I gave it a little Mask Blur and I'm feathering this so that it applies mostly to where there is Milky Way, and then I'm going to take the Subtract and turn it on very lightly.

I'm going to go with that: 7%.

Before, and after.

Now, I mentioned doing a Multiply on the entire image.

I'm going to do that with a Parametric Mask.

I'm just going to apply a straight L Channel from no application to the darkest parts, to full application to the lightest parts.

Then I'm going to change the Blend Mode to Multiply and I'm going to adjust how much of it gets used by the Opacity Level here.

Let's see what we've got.

Before, and after.

Okay, that's it for this.

I'm going to Save it again.

Alright, here we are.

It's been Saved and we're starting again.

On this time, I'm going to fill my Histogram a little better.

I'm going to darken the sky just a little bit and bring up the Milky Way just a little bit.

I'm going to try to enhance the Milky Way using a Soft Light.

Take my Radius, get it so I'm getting good areas of color in the MIlky Way, and take the Contrast and get it so that I'm going to get good differentiation.

Take my Saturation and turn it down because, if you're using Soft Light, you need to turn your Saturation down to half.

Otherwise, it just gets silly.

Before, and after.

Well, that looks pretty good.

Now, I don't want it to work in the trees, once again, so I'm going to use a Parametric Mask.

That's a little too much effect.

Maybe that looks a little better? Yes, that looks a little better.

I used the Opacity and turned it down to 66% to make it look a little more realistic.

Now, I'm going to work on some final Sharpening and then I'm going to shape the stars, do a crop, and change my Blackpoint, and I'm done.

So, this will be the last Save.

Alright, here I am.

This is the last Save.

We're going to make these changes.

First thing I'm going to do is look at cropping it a little bit.

That looks good right there.

Next thing I'm going to do is enhance the edges of these palm trees using the Highpass Filter.

What I want to do here is only have the edges that I want to enhance.

So, no other details.

That's about it.

That gives me these edges of the leaves the best.

I'll use an Overlay and I'll have to turn that down quite a bit.

Okay, now I don't want to use it on the stars.

See how it makes the stars just too bright? So, once again, I'm going to use the Parametric Mask to isolate the trees but what I'm going to want to do when I get down to the point of the trees is I'm going to want to use the Mask Blur so that the sharpening extends past the tree limb a little bit.

There we go; that's more like it.

See these little yellow dots out here? So I'll have to combine this once again with a Drawn Mask.

Before, and after.

That helps define the edges of these leaves.

There we go; that looks good.

Okay, next thing is the final sharpening with the Equalizer.

Put it on Luma, And that looks good.


Next thing I want to do is shape the stars.

I'm going to do that by using the Darken Blend Mode.

So, I'll set a Radius really small: 0.8 What that does is it fills in the stars with a little fuzzy area.

Now, if I use this Darken Mode, what will happen is, anywhere where the original pixel was darker, it will use the original pixel, and anywhere where the Lowpass solution is darker, it will use that.

Here's what it looks like originally, and here's with the Lowpass.

So, if I say Darken, it doesn't change the outside of the star, but the inside of the star fills in a little bit.

The color comes toward the middle and it starts to look like a light shining on a cue ball, where you've got, instead of just white in the middle, it's a smoother gradation.

Now, I find that I lose a lot of color when I do this, so I have to turn the Color up to twice as much.

Before, and after.

I think I'm going to apply this again to get more of an effect.

And once again.

Okay, now let's look at our stars before.

We'll take a Snapshot.

And this is after three passes of the star Sharpening.

See, we've got nice rounded stars, and they have color all the way through them.

It makes for a more pleasant sky.

Nicer looking stars, especially these really bright ones.

Before, and after.

See, that helps a lot.

What else do we have on our list here? Change our Blackpoint, and we're all done.

We'll bring our Blackpoint down.

Try and maintain some lightness in the tree trunk.

One last thing I'd like to do; I'd like to take a little bit of the color out of the sky so that there's more differentiation between that and the Milky Way.

So, I'm going to try and select for the sky based on its brightness and its color, and then reduce the amount of color it has.

So, I'm going to take the Parametric Mask and I am going to take my Eyedropper and put it right here in the sky.

Let's see.

Here's a good area of sky.


Take my Mask and Blur it some, but not too much.

I don't want to take the color out of the stars.

So, maybe just 0.8...

0.5 That looks good: 0.5 Okay.

Now, I'll take my A and my B Channels and I'll bring them way down.

That reduces the Saturation in the sky area that's not the Milky Way.

Before, and after.

I think I'd like to darken up some of these areas just a little bit.

Ah, yes; I messed up this Parametric Mask by moving this Tone Curve.

That's why these red dots started to show up.

Okay, that looks better.

And, I don't think we're damaging any of these stars.

Alright; that's it.

I hope you all enjoyed that.

Oh, I forgot to mention: there's a link to the original RAW file.

If you want to follow along, you can do that.

It's in the Notes.

Thank you.

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