Tag Archives: masking

Darken Mode Stack Tip Using AdvancedStacker PLUS 15

The new Advanced Stacker PLUS 15 is our attempt to make processing simpler. One of the things we find we often do is run multiple stacks (Lighten, Darken, Streaks, etc) to determine which effect(s) work the best. Well, we did something for the first time that worked REALLY well, so we will start by sharing that, even though Advanced Stacker PLUS 15 is not yet ready for publication.

In a nutshell, we created this:

Orion, Falling

From this:

Long Streaks Stack Result – no modifications  f/4, ISO 1600, 15 Seconds. Nikon D600, 24mm x 250

There are several obvious differences between these images.

  1. Because there was strong moonlight (and other light), the sky is over-bright and lacks contrast.
  2. The wind together with surrounding lighting (including flashing red lights from a passing fire truck) caused strange artifacts in the palm trees.
  3. Different colored light sources lit the palm trees differently (notice the really cyan colored palm fronds in the second tree from the left).
  4. There was utility wiring intruding into the image.

The Processing

Stacker 15 allows you to simultaneously stack in multiple modes. For example, to create this effort I used Lighten, Long Streaks, Darkest, and Average modes. I ended up NOT using Lighten or Average modes in this case. Is there extra overhead keeping more stacks? Yes, there is. However we’ve paired down the stacks to as few frames as possible to keep the overall footprint low.

Once the stacking had finished, the result of the Long Streaks was a bit unappetizing due to the red and other artifacts in the trees (see second image). However the Darkest mode stack effectively removes all of the stars – and as it happens, all of the strange highlights in the trees.  First we applied a Curves adjustment layer to the Long Streaks and darkened it.

Blending a Clean Foreground with the Star Trails

Darkest Stack results

The next operation was to find a way to blend the darkest mode stack (right) with the Long Streaks stack while preserving the star trails  and getting the cleaner looking foreground.


Duplicate the Darkest mode result (it’s a single layer) on to the Long Streaks stack. Then drag the darkest mode stack to the top layer. Set the new layer blend mode to normal, 100%.

Next we need to mask out the sky of the Darkest stack so that the long streaks will show through. The tool for that is to use Select -> Color Range. Holding down the shift key allows you to click multiple areas of the sky to add to the selection. You can vary the fuzziness of the selection to determine how closely the color has to match the sample. The mask will probably need some manual cleanup afterward, but as you can tell from the selection in the image below, just clicking different areas in the sky produced almost exactly what is desired.

Photoshop Color Range Selection

After pressing OK you get a selection. The next step is Layer -> Create Layer Mask from Selection -> Hide Selection Once you have a mask, you can paint on it to clean up any artifacts. Adjust the opacity of the darkest layer to make it “look right”. In this example, the combined image looked best at about 93% opacity.

Correcting “Off” Colors Due to Light Source Issues

The penultimate step was to create a Hue and Saturation adjustment layer. Lock the adjustment to the Darkest layer (hold the Alt/Option key and click on the boundary between the adjustment and the darkest layer). Then click the “Finger selection”  (just below the word Presets). Now there is an eye-dropper which you use to select the color that needs correction. In this case, clicking the dropper on the cyan colored palm frond is the right move. Adjust the saturation slider way down, lightness down, and fiddle with the hue to make the bizarre color more natural.

Aggressively toning down the cyan colored palm fronds

Removing Wires (and other distractions)

Finally we also used the Spot Healing Brush tool to “heal out” the utility wires. Here is a short-cut for healing out a straight line. Click the beginning of the area with the spot healing brush, then hold shift and click the end of the line. Shift causes the brush to be applied in a straight line between the first and second clicked points. The shift-trick works with almost all brushes. Two other tricks with the spot healing brush tool are to:

  • Start where the surrounding area has a predictable substitution (not a busy area) and work outward from there
  • Use as small a brush as you reasonably can

For example you can adjust the spot healing tool brush size to about double the width of the utility line, then click the healing brush tool where the arrows point below. Next work your way outward toward the tree on one side, then the other.


Here is a summary of the steps taken – not including the palm frond “naturalization” or spot healing described above.One more trick worth noting… the histogram shown on the Curves adjustment will give you a clue what may need adjustment.

Want to know what we consider the top 5 most used photo editing skills? Read here (and part 2 and part 3).

Adding Special Touches to Your Astro Landscape

1000 ISO, f/2, 3 minute exposure with some augmented stars

Because stars are pinpoints of light, the camera does not capture them as our eyes see them. To our eyes, brighter stars stand out more noticeably than dimmer ones. At a workshop in Alabama Hills, one of the participants, Julian Köpke, was using a diffusion filter so the stars captured would look more like you see with the naked eye. Sometimes nature provides its own diffusion filter in the form of high, thin cirrus clouds as shown below. The large bright orb is the star Sirius in the constellation Canus Major (Big Dog). The orange star near the top of the frame is Betelgeuse in the constellation Orion. One nice thing about the blur that the clouds added is the star color is more noticeable. But the diffusion here is not uniform because the belt stars (Alnitak, Alnilam and Mintaka) and “corner” stars (Bellatrix, Rigel, Saiph) in Orion are all noticeably brighter than the surrounding stars while in this photo only Betelgeuse and Rigel stand out.

Dog Star [C_065586]

You can create a make-shift diffusion filter by shooting through a nylon stocking – or buy a diffusion filter. The disadvantages of using a filter are that everything is blurred – including the foreground and you reduce the amount of light collected. Most night sky photographers try to avoid clouds and you will get an image like this:

The moon and Teapot Asterism in Sagittarius – over Lone Pine Peak – as shot.

When what you had in mind is something like this:

Same Photo as above, but with the Teapot Asterism in Sagittarius enhanced.

How to Bring Out Star Color And Enhance The Apparent Star Size

Our Advanced Stacker Plus has two built-in ways to increase star brightness. We call those Bump Up and Pump Up the stars. Bump Up creates a small blur by literally duplicating the shot , nudging the duplicate(s) and recombining .  Pump Up is more sophisticated and tries to find the stars so it can then apply enhancements to just the stars. But there is a new tool in the arsenal that I have begun using: Star Spikes Pro from ProDigital Software.  Version 4 is the latest as of this writing.

NOTE: Star Spikes Pro and HLVG described later are currently only available on Windows machines.

You can use the Star Spikes Pro plugin to add diffraction spikes and diffusion. The most common diffraction spikes you see with stars are due to obstructions in the telescope used to photograph them and many people come to think of the spikes as evidence of astrophotography.  You can create diffraction spikes easily on your own.- just stop down your aperture;  however stopping down to make stars create those spikes will not work well.

The first time I tried to use Star Spikes Pro it did not quite work as I expected.

Look hard. Star Spikes Pro decided the moon was a huge star outclassing all others.

Indeed it took me a bit to realize what was going on. The good news is it was easy to work around. The huge moon looks like a huge star to Star Spikes Pro – and that makes perfect sense since the plugin is usually used with Astrophotography that does not involve landscapes.

Here is how I made it work as I wanted and limited the effect to just the desired stars.

Layer Palette and Steps to Enhance The Teapot Asterism

Above left is the layer palette. Look carefully and you may spot the fix. After loading the image (1) I first duplicated the original and called the new layer Heal (2). I then did minor contrast adjustments, used the healing brush to remove hot pixels and other offenses (short satellite trail). Next I duplicated the Heal to another layer (3) and fed it into Hasta La Vista Green – a free plugin written by Rogelio Bernal Andreo of DeepSkyColors. HLVG removes green which is an unnatural sky color usually caused by RGB artifacts. HLVG operates on the entire layer and does not know the difference between land and sky. To leave the natural green in my landscape I used the quick selection tool, dragged it across the sky followed by Select -> Modify -> Expand 4 pixels. Then I created a Layer Mask using “Reveal Selection” (4). That made the foreground come back to its normal state. If you look carefully you will notice I also used a white brush to add some of that green removal back onto the mountain by painting on the HLVG layer mask (4).

The next operation was a finger twisting sequence that has no menu equivalent: Ctrl-Alt-Shift-E (on Mac that’s Command-Option-Shift-E). What that sequence does is “flatten” all the visible layers and create a NEW layer in the process (5). That layer I called Input to SSP.  Since I had discovered that Star Spikes Pro was confused by the moon (and could be confused by the foreground), I used the quick selection tool again and brushed it across the foreground. By default using the quick select tool again ADDs to the current selection so I brushed it around inside the moon and its halo. At this point I did not need to create another layer (Ctrl-J/Command-J or Duplicate Layer) but I did so that it was easy to see what happens next. After creating the new layer I selected it and used the delete key. Delete removes the selection making it transparent – that is the foreground and moon were now gone (6).

Next up: let Star Spikes Pro loose on the image. First deselect (Ctrl-D Command-D) or Select -> Deselect), and feed the sky layer to Star Spikes Pro via Filter -> ProDigital Software -> Star Spikes Pro.  The defaults for SSP produced the image below (I’ve zoomed in on the teapot asterism)

I felt the color was a bit too strong, and I did not want the diffraction spikes. The next step was to select “Advanced” – just below Settings, set the Primary quantity to zero. Next was the Secondary tab where I reduced the quantity to 44, the intensity I bumped up to 23. Soft flare I set quantity to 12, bumped up the intensity, dialed down the size a little and dialed down the Hue to -21. These adjustments were all based on eyeballing the image and were made for aesthetic appeal.  After all the adjustments looked about right, I saved the settings as a new adjustment I called “DiffusionOnly”. Finally I clicked OK and my layer was all nicely done by the SSP filter.

The filter processed a few more stars than I intended to augment. The simple solution was to create a “Reveal All Layer Mask”, select a brush, the color black and paint out all the effects I did not want on the layer mask (7).

The final operation was to use an Adjustment Layer (8) to increase the contrast and restrict that adjustment to the sky (where you see white) and tone the adjustment down a little with a low-flow back brush on one area that looked a little too dark.

The topmost layer in the layer palette is my watermark.

There Is An Easier Way!

With some experimentation, and some coaching from the plugin author I discovered that Star Spikes Pro has several features that make the process easier than I imagined. Instead of creating the transparency (deleting the moon and landscape) I only needed to select the area I wanted Star Spikes Pro to operate on.

Also, instead of masking off the stars I did not want affected after the fact, Star Spikes Pro has two tools to greatly simplify things the: “Hide” tool to turn off any effect that I did not want, and the “Show” tool to turn the effect on.


Star Spikes Pro limited to specific section of the sky via a selection and using the Hide tool to turn off an effect.


The net is that you can get that nice diffusion effect for your stars without having to compromise by shooting through a diffusion filter. However if you DO want to try a diffusion filter, I recommend you take two shots quickly. One with the filter off, one with the filter on. You can then place the diffused shot over the normal shot. Set the diffused shot to Lighten and mask in (or out) the areas where you want the diffusion to show through.

If you’re wondering whether there is a way to get the diffusion effect on a Mac or without purchasing Star Spikes Pro, there is, but it requires a lot of Photoshop twiddling and it is not anywhere near as pleasant as using ProDigital Software’s Star Spikes Pro.

Disclaimer and Book

I am not affiliated with ProDigital Sofware. I am a happy customer of Star Spikes Pro (and another product called Astronomy Tools). I was not paid, or encouraged to write about the product. I chose to because it is that good. Rogelio Bernal Andreo  author of Hasta La Vista Green and purveyor of DeepSkyColors is a friend and a multi-multi award-winning astrophotographer. He has a Kickstarter Project that I recommend you look into called Notes From the Stars

Notes from The Stars: 10 Award Winning Authors

Blobulous Revisited – Part 2

Last installment we covered the basic idea behind creating a star trail where a foreground element is moving. In this case the moving element is a radio telescope peering into the sky to discover planets and black holes.  A normal “lighten mode” stack produces the image at the left, below, while with just a little bit of work we can get the image on the right.


To recap, we use a single frame from the sequence and some careful masking to remove the blurred part of the image. For effect, we also don’t use the stack in 100% mode. See the prior article for details.

In this article we’ll show you step-by-step how we achieved the total look.

Of course we start with the stack.


Then we layer in a copy of the stack and a single frame (the last or nearly last frame).


Here we have set the background (stack) to 36% Opacity, effectively darkening it. The single frame is 100% opacity and in Lighten blend mode. What we want to do is to remove the blurred part by replacing it with the unblurred single image. It’s easy to do. Select the STACK, create a “Reveal All” mask, and then go to town painting black on it (be sure to select the MASK, not the image). When done, the mask we create will look something like this:


Notice how we used a slightly soft brush to “blend” the background and the still frame. We could stop right there, but I notice that the ground and the telescopes are a bit too bright, and I’d like to make the stars pop out. So the next course of action is to apply a curve, select the “Increase Contrast” option. Here I’ve adjusted the result just slightly.


Next we want to tone down the bright stuff. We add another adjustment layer, and a “Hide All” mask and then paint white back on the mask to tone down what we want. You’ll notice that in the process, the colors intensify a bit.


The next step we’ll want to take is to reduce the saturation – our radio telescope is moving from white to yellow. So the next step is to add a Hue and Saturation layer. As before we mask off everything, and then paint in only the radio telescope. We could cheat and use the same mask from the Brighten stack layer – and just invert it, but it’s not a complicated thing like a tree, so it’s pretty easy to change the mask to only operate on the radio dish and pedestal.  At the left, you can see how strongly we moved the saturation – and we upped the brightness a bit, too.


If we didn’t mask off the telescope and instead applied the saturation adjustments globally, we’d see this – not what we want. (Shift-Click on the mask turns it on or off – in this case we see that the mask is off by the red X through it)


You won’t notice in the small size, but the large image has a number of Hot Pixels (red, and blue) that stand out. To solve this problem we use “Alt-Ctl-Shift-E” (Command-Option-Shift E for you Mac-o-philes) to make a copy of the layer. I named the layer “Heal” because I then used the spot healing tool to fix up those little problems.  I recommend making the healing tool diameter just slightly larger than the area to be healed.


To make the Radio dish pop just a little more, a little sharpening is in order. In fact, sharpening the ground will work, too.  Duplicate the Healed layer (Ctl-J or Command-J). Name it Sharpen then use Filter -> Sharpen -> Smart Sharpen.  However I don’t like sharpening my stars, they look harsh. As before we’ll create a Hide-All mask for our Sharpened layer and use a white brush to reveal the areas we want to have sharpened. This is called selective sharpening.  In the small image here, the effect is not as obvious as in the larger image.


To get just a bit more pop, a little more contrast is in order. I created a curve and pulled up the midtones a fair amount while making minor negative adjustments to the highlights and the darks.  But, that adjustment brightened some areas a bit too much so I created a reveal-all layer mask and painted black on the areas that were then too bright.


Et Voila, we’re done!


Blobulous Revisited – Part 1

It’s pretty amazing what you can accomplish with just a little bit of effort.  Below you’ll see a star trail formed using the Blobulous technique that I described in an earlier column on Advanced Star Trail Tricks.  There are many ways to achieve this effect. The method I described in the prior article – adding the last frame using Screen or Add blending – works especially well if the skies are dark. But here, I used high ISO shots about an hour before moonrise. Because of the high ISO exposures with a soon to rise moon the sky was blue not completely dark.  Adding the last frame to the stack as described earlier will work but it makes the Milky Way blow out and the sky overbright. I wanted the Milky Way to remain noticeable.


Selecting Images to Work With

There are few important things to note here. The radio telescope tracks the sky and slews from location to location causing blur. Each 20 second exposure was shot at ISO 3200, f/2.8 using a 15mm fish-eye lens on a Canon 5D Mark II. I carefully picked a range of images where the start of the sequence through to the end of the sequence included only images where the dish did not move “too far”. The next four frames show how dramatically the dish moved in subsequent shots. Had I included them it would have made quite a mess.


The dish moves far in 80 seconds…

To say it clearly: looking at the individual frames is what allowed me to zero in on the specific images I planned to stack. After selecting the range of images (C_072887 to C_072935),  I stacked them using good ‘ol brightness mode stacking. You can stack using a ton of methods but our favorite, of course, is to use the Advanced Stacker+ from StarCircleAcademy.com though the free TEST Stacker can do the job, as can a variety of free tools that we describe in this article and in our Star Trails Webinar.

To create the shot below on the RIGHT you’ll need Photoshop or some equally featured program that allows layering and masking like GIMP. Even the lowly, stunted Photoshop Elements will do the trick. After doing a normal brighten mode stack, the output looks like what you see on the left.  After some image manipulation magic, we achieve the result on the right.


Before (left) and After (right)


It would be tedious to show step by step what I did, so I will start with a “one shot” view. You’ll notice there are 9 layers that contribute to the final image.  The top – SLC-SCA – is obvious, it’s my watermark.

Results with all layers shown.

Results with all layers shown.

However you can also see the brighten mode stack (at the bottom), and a copy of that same stack with a layer mask.  If you look carefully it’s pretty obvious that the black on the mask corresponds to the upper part of the moving dish.  Sharp eyes will notice two additional blacked out parts corresponding to the other radio dishes.  Notice that above the stacked layer is a single frame: C_072934 – the next to last image from the set used in the stack. All the layers above the single frame are adjustments to correct color, white balance, hot pixels (the Heal layer), and to do some sharpening.


The single frame (934) is blended in Lighten mode with the stack. The stack is at 36% opacity.

The essential bit of magic here is that the Brighten layer is only used at 36% opacity. 36% was chosen by eye. I slowly reduced the opacity until the Milky Way became noticeable rather than a blur and yet the star trails remained noticeable.

The image was nearly complete by painting out (excluding) the blurred stack areas using a black brush at 100% opacity with a small amount of feathering – i.e. a brush that was not 100% hard.  It’s easy to paint on the mask and watch how the blurry dish from the stack is replaced by the non-blurry single image from C_072934.  If you’re wondering why I didn’t use the final image, C_072935, it’s because it was a tiny bit blurrier than the preceding image.

The rest of the adjustments are straight forward – they were all meant to fix contrast, darken the overbright areas and then correct for the color saturation increase that occurs when you darken an area with color.

We cover complete details in the PhotoManipulation webinar series.

Here is the image obtained from the next set of exposures after the dramatic dish move. This image used the “Streaks” stacking method available in the Advanced Stacker, but is otherwise identical in creation.


For yet one more take – using yet another Advanced Stacker Mode (long streaks), there is this.

Long Streak Runnin'

In the next column I’ll show all the steps I took to produce the first image on this page.