Tag Archives: layers

Sneaky Night (and Daylight) Photo Processing Tips


Did you attend the Sneaky Night (and Daylight) Photography Processing Tips event held at Adobe in San Jose, California on July 23, 2018? Welcome!

The topics covered include these:

Let’s Start With a Pop Quiz

The Equation…

Or asked another way. Do these look like they might be the makings of an interesting shot?

Three Nuns Thumbnails

The Answer To the Pop Quiz

Combining the images shown in the thumbnails, nets this Interesting star trail.


“Long Streaks” Star Trail from 112 separate photos

Creating the Star Trail component above is discussed in detail in our NP105: Creating Star Trails & Timestacks Webinar – it’s an interactive 2 hour course with notes, a recording, and practice files. We run that webinar approximately quarterly next event is July 25th. Details  covered include how to set up the shots, configure the camera settings, and combine the images using various tools.

Adding that bright frame with a bit of selection and masking to the star trail image nets this:Reaching for the Sky

And that MUST be interesting because it garnered 80,000 views in just a few days. How do you do this bit of Photoshop Magic? Over the years, we’ve shown quite a few methods for accomplishing this. For example in Foreground – o – Matic we illustrated how to use the quick selection tool. That may work well here because the rock has a nice crisp boundary. Other methods that may work include “thresholding” and Color Range selection.

Thresholding to create a mask:  We’ve described this before. Briefly this is how it works. Select one of the images – one with contrast between the sky and foreground.  Duplicate that image (Ctl/Cmd -> J). Then use Image -> Adjustments -> Thresholds and slide the carat left or right until it has selected what you want (mostly black or white). Paint out the stray areas with either a 100% black or white brush as appropriate.  When done, you have an image you can use as a layer mask. The trick to doing this is to select the black and white image, EDIT an existing layer mask, and paste the black and white image as the layer mask.


Photoshop Processing Tips

  • Do work on a calibrated free-standing display in a dim, consistently lit room.
  • Do NOT attempt to process important images on a laptop monitor. You will frustrate the dickens out of yourself trying to get consistent color, brightness, and so forth on a laptop monitor or in an uncontrolled lighting environment. The monitor display angle can cause subtle to dramatic differences in color, saturation, brightness.
  • Do make an action and assign it to a hot-key if you find yourself repeating that operation frequently… E.g. I have an F9 key to apply a contrast enhancement adjustment curve
  • Do name your layers sensibly. You may save yourself a world of hurt.
  • Do NOT crop too early – save this step for last.
  • When combining dark and light subjects (e.g. daylight-like and night) it’s usually best to have very crisp selections – not feathered selections.

Gallery of Photoshop Hot Keys

These hot-keys are described for Windows users. I use these ALL the time. Some have no menu equivalent. You can translate from Windows to Mac as follows:

Ctl -> Command
Alt -> Option
Shift -> Shift

Layer / Layer Mask shortcuts:

  • Duplicate layer dialog allows you to duplicate into another/new document!
  • Ctl-J: Duplicate the current layer
  • CtlAltShift-E   Merge visible layers to a new layer as a COPY.
  • Shiftclick on layer mask to turn it off or on.
  • Ctldrag layer mask to move it to another layer.
  • Shiftdrag a layer mask to Invert it and move it to another layer
  • Altclick a layer mask to EDIT it.
  • Altdrag a layer mask to copy it. Toss in Shift to invert the mask.
  • Shiftclick a layer mask to turn it on/off
  • Altclick quick mask icon to create an inverse layer mask from a selection
  • Do not be afraid to duplicate and adjust a layer for the sole purpose of creating a mask!

Selection shortcuts:

  • Ctlclick on layer mask to create a selection from that layer mask.
  • Ctlclick on a channel e.g. RGB, R, G, or B to make a selection based on brightness.
  • Sometimes Select -> Modify -> Expand or Contract (by 1 pixel) helps to fine-tune a selection. Feathering seldom works well for compositing light and dark images.

Sneaky Tips
Sneaky Tips
Notes from "Sneaky Tips for Processing Day and Night Photography"

Tips for Using Layers for Stacking

Down Range

With hundreds of users of our Advanced Stacker PLUS, we get questions about workflow. What is the best way to manage files in Lightroom? What order should I perform operations, etc. While we have briefly given some hints in the comments for the Advanced Stacker, it seemed time to elaborate.

Of course it all begins with how you choose to organize your files. Organizational tips will come in a separate article as it would make this article too long.  Unfortunately Lightroom is not a particularly helpful tool to use for creatively stacking shots and that’s one of the reasons I don’t much like it. For my money Adobe Bridge is more powerful and flexible.

One particularly insightful exchange was with Dan B who wrote:

One minor gripe I have mostly has to do with incorporating the action into my existing workflow. For star trails my current workflow starts in Lightroom where I do any preliminary adjustments/corrections and then open the sequence as a layered document in Photoshop. I created a layer style which is my one-click way of changing the blending mode to lighten on all of the layers. Unless there is a way of applying the action to an already open layered document I would presumably have to adjust my work flow by moving the star trail sequence to its own folder, doing preliminary adjustments in ACR and then using the action as directed.

Beginning in Photoshop CS6, you can do a one button change of all blend modes and opacities of all selected layers. You can select all layers with Alt-Ctl-A  (Option-Command-A on a Mac).

PSMultiLayerOperation PSMultiLayerOpacity

The change applies to all selected layers.  Setting all the opacities the same won’t provide the nifty comet-style stacking.  There are some scripts out there to address variable opacity and other stacking tricks but there are restrictions. Installing a script isn’t always easy – depends what version of Photoshop you have, and no script I’ve seen is able to work from files. Scripts work on Layers. Scripts by design aren’t really meant to tackle repetitive tasks against a large number of files – that’s why actions were created.

Summary: There are two options: work on layers (actions or scripts) or work on files (actions).

There is no equivalent in Lightroom to do Photoshop Batch operations like you can from Adobe Bridge, and that’s unfortunate.

Another observation is that loading files into a stack in Photoshop and then editing individual layers is, SLUGGISH unless you have few layers – see later for just how sluggish.  Why would you edit layers? You might edit individual layers to remove things like airplane trails or bright light sources. Airplane trails are a lot easier to remove from individual documents than to remove after the stack has been created. However my recommendation is: don’t do editing in layers. Export the documents to TIFF or JPG and edit them individually. Why? Because then you can use the edited files standalone or stack them in different ways and NOT have a huge layered document. You also have more flexibility to use programs like StarStax which do not work well with RAW files (StarStax does not know how to apply all of your ACR or Lightroom edits). Alternatively, you can load files into a layered document, edit the layers and then use a script (Export Layers to files) to save layers as individual files.

Load Into Layers from Lightroom


Save From Layers into Individual Files


If you save from layers into files, Lightroom will not know where those saved files are unless you Import or Resynchronize the folder where the files are saved. Bridge, on the other hand, doesn’t require importing or synchronizing – though you may need to do a refresh operation. By the way the Photoshop “Export Layers” operation insists on adding a number prefix to each of your files… and it will make a mess if the opacity of each layer is not 100%.


If you want to do your stacking using layers, there is one more thing that might change your mind… speed.  We ran speed tests on two different machines comparing the end-to-end time needed to create stacked documents using the layering method with the automated Advanced Stacker Plus.  We were shocked by the difference.  For each machine we stacked 60 RAW files from a Canon 5D Mark II. In each case we applied a linear adjustment to all files, and made a tweak to the color balance.  We drove the layering method using Lightroom 5’s “Edit as Layers” operation. For the Advanced Stacker PLUS we drove the operation using Adobe Bridge CC. We kept Bridge CC, Lightroom 5, and Photoshop CC loaded in each machine so that the same starting memory footprint was used. And to make sure there was no advantage from using pre-loaded files, we used a different set of 60 files for each comparison.  The file sizes were identical.

The less speedy machine was a quad core AMD Phenom II processor with 6Gb of memory, Windows 7 Home Premium, 64 bit. The new machine was an Intel I7 quad core machine with Windows 8, 64bit, and 12 Gb of memory.

On the lower end machine it took 33 minutes to load 60 Raw files as layers, change all the layers to blend mode Lighten* and merge those layers. There was HEAVY swapping and the machine was extremely sluggish.  Using the Advanced Stacker PLUS to perform the same result took 8 minutes and the machine never became unresponsive – because there are never more than a dozen layers in memory.  The Advanced Stacker PLUS took 76% less time!

*NOTE: In Photoshop CC and Photoshop CS6 all the blend modes are changed with one Select All Layers command and one blend mode change.  On the sluggish machine it took almost 2 minutes for the “Select All Layers” key sequence to complete!

On the faster machine the results were similar: it took 19 minutes to load all the layers, change the blend mode and merge the visible layers into a single image for saving while it took 3 minutes to use the Advanced Stacker Plus.  On the 12 GB machine there was some pretty heavy disk operation going on when using layering, but memory did not top out. The Advanced Stacker PLUS took 80% less time.

In each case, adding more layers will make the stacker speed advantage even greater because once the machine maxes out memory it becomes a performance dog.  We’d love it if you’d run a comparison on your hardware to see what your results are like.

In Summary

There are many folks out there who are proponents of stacking star trail shots using layers. I’m not a fan.  Certainly using layer provides some benefits, but it also comes with some (high) costs.  Here are some tradeoffs to help you decide whether layering shots in Photoshop will be more effective for you or not:

Layer When

  • You have LOTS of memory and patience.
  • You have fewer than about 30 layers (shots) or your individual shots are small.
  • You don’t expect to save the final image as a layered document (only .psb files allow sizes big enough to hold a typical layered document)
  • You don’t mind throwing away any editing you do in a single layer (e.g. removing plane trails, stray light, etc.)
  • You don’t mind manually updating blend modes and opacity or finding installing and using the (very few) tools available to help with layer adjustments.
  • You intend to do something totally different from all the currently popular effects (Comets, streaks, etc.)
  • You don’t plan to make a timelapse – or if you do, you can live with the restrictions created by a layered document.

Stack via an Action or External Tool When

  • You have a boatload of images or limited memory.
  • Want to create intermediate images for timelapse/animation.
  • You intend to pre-edit individual frames to clean them up before creating a final version.

Advanced Star Trail Tricks

Published: Oct 11, 2012
Last Update: May 2, 2021 (remove obsolete)

I have been playing with Star Trail processing for quite a while.  Ever since I wrote the StarCircleAcademy Stacking Action I’ve been tweaking processing to try different things. Sometimes failure is inevitable, sometimes… well, you’ll see.

First, you may want to look back through my earlier columns on shooting and processing star trails because this is not a primer on star trails – it builds on what I’ve previously written and this is not a good place to try to understand what stacking is.

Second, please understand that I use a variety of tools but almost all of my more successful endeavors end up as layers that are combined in Photoshop (CS5 at the moment).  You could combine your layers in GIMP if you don’t have Photoshop, but you’ll be out of luck if you try to use Lightroom.

Here are my star trail effects:

  1. Smoothee – Averaged sky and/or foreground to reduce the grittiness that sometimes results from brighten stacks. I’ve been espousing this for quite a while. See the Simple Astrophotography Processing Technique.
  2. Blobulous – stars at the beginning (or end) of a trail are made to stand out from the rest of the trail.
  3. Comets – star trails appear to grow brighter and the end of the trail looks like the nucleus of a comet.
  4. Streakers – Like comet only the trails are longer
  5. Blackened – A clever trick removes sky glow from light pollution, the moon, or twilight.

And of course you can make “Blobulous Comets” and “Blobulous Streakers” and “Blackened Smoothee Comets” and more.

Building Blocks

To creatively combine exposures, I usually create the following stacked frames.

  • Dark (Darken in Image Stacker/StarStax)
    The darkest elements emerge – especially the hot pixels
  • Brighten (aka lighten) stack
    The Brightest of everything is present, including hot pixel and more noticeable noise
  • Average
    Contrast is reduced, smoothness increased.
  • Additive (called “Stack” in Image Stacker)
    Hot pixels become really bright.
  • Scaled (called Stack/Average in Image Stacker)
    Allows some increase in brightness but more smoothness, too. Experiment with different divisors.

Normally I create all of these combinations using Image Stacker against my JPG files because it is really easy to do.  I end up with a set of frames something like these although I’ve significantly brightened them so that they are easier to see.


In a Nutshell: Combine the Average stack over the Brighten stack using Normal mode at 45% opacity.

I’ll start with the Smoothee technique since it’s probably the easiest to do and perhaps the easiest to understand.  The problem with “Brightness” (or lighten as it’s called in Photoshop) is that it will also pick up all the hot pixels, and the brightest bits of noise.  Averaging on the other hand tends to smooth out everything except for truly hot pixels since most noise is random. By putting an averaged stack as a layer over the brighten stack and then adjusting the blending modes and opacity you get a smoother sky and foreground.  Exactly what settings to use depend on the images, but surprisingly many of the blending modes for the Average layer work here including Darken, Multiply, Overlay, and Normal. The starting place for Opacity is about 45%.

Hint: You can also use an Additive stack instead of the average stack but usually only the Normal blend mode will work.  For even more fun combine the Additive stack and the Average stack.

For additional smoothness you can also subtract the “Darken Stack” while adjusting the opacity to prevent halos and weirdness.


In a Nutshell: Add one of the single frames more than once.

What do “Blobs” look like? Like this…

“Fat Star” processing.

There are two ways to produce “Blobs”. One way is to add “Comets” to a smoothed star trail. The other is to simply pick an image (usually the last one in the set) and add it in using “Add” or “Screen” mode. To make the blob more pronounced duplicate the last frame so it’s added twice. BUT remember when you add in any single image the hot pixels are going to come out… and even more so if you add an image twice.

Comets and Streakers

These two techniques require some fancy stacking techniques. Fortunately I’ve created an action to do all the fancy stuff – but it has been withdrawn from sale because it became too tedious to keep it up to date (especially on a Mac).

Oh, here is a peak at what the Comet action looks like:

What's The Point?

And here is what an animation of comets might look like:

Star Rise


I know you’re going to ask so let me save you some typing. Except for the “Comet” image above, all images used in these illustrations were taken during the Ancient Bristlecone Pine Workshop in the Patriarch Grove on White Mountain, East of Bishop, California.

The 34 or so images that I’ve combined in the examples above were all taken with the following settings: Canon 50D, ISO 400, f/3.5, 79 seconds, 10-22mm lens at 15mm.

Simple Astro Processing Technique to Conquer Noise

Published: Jun 20, 2012
Last Updated: March 5, 2017

Is one of these your scenario?

  • It’s really dark. The ISO is bumped up, the noise is screaming at you, but you REALLY want the shot.
  • The Milky Way looks SO gorgeous, you want to take it home with you like a trophy, but when you shoot short enough exposures to prevent smears, mostly what you get is noise.
  • You are surprised that you can faintly make out the Milky Way. You know your buddies will be jealous if you can show them a photo of the Milky Way that you took from IN TOWN. They won’t believe you!
  • You have a great star trail, but your foreground is not lit. The photo would sing if you could tease out that foreground – minus the noise, of course.

In the Star Circle Academy’s “Astrophotography 101: Getting Started without Getting Soaked” webinar we cover all the theory and equipment you need to take gorgeous photos of deep sky objects (nebula, galaxies):

Colorful Neighbor

But absent the fancy equipment, all you need is a wee bit of Photoshop skill to get a pretty compelling image. Less than 10 miles away from Palo Alto, California, with over 8 million households in a 50 mile radius I got the image you see below. I understand why you might not believe me.  Is it the most compelling Milky Way you’ll ever see – definitely not.

Urban Milky Way [C_036919-23PSavg]

Here is the best I could do with a single image from the same location:

Milky Skyline [5_006550]

After much processing it’s still noisy (grainy) and contrast poor.

We covered the processing technique in our Night Photography 150: Photo Manipulation I Webinar – among many other topics. Below is a 7 minute video describing how to do that simple astro photography processing.

If you think a webinar on photo processing would be of interest, join our Interest List for this or other topics and you’ll be notified when we schedule the next webinar. You can influence the topics we choose to cover by making your comments here.

Simple Astro Photo Processing in Photoshop CS5 from Steven Christenson on Vimeo.

NOTE: If the above says password required, enter scanp150 In the video, you’ll also learn how to constrain the healing tool, use curves, layers, and the history tool to undo inadvertant changes.

ALSO NOTE: Advanced StackerPLUS has a built in averaging operation. You just feed it the images. It does NOT do auto alignment, however.

In our next installment, we will talk about how to get the Milky Way shots in the first place. Camera considerations, settings, tradeoffs.

By the way, this image consists of a single sky shot and a multi-processed foreground using the technique described above. Click the image for further details.

South Side Truckin' [C_009842]


We have another video tutorial that uses some similar processing techniques:

12 Minute Star Trail using Advanced Stacker PLUS version14D from Steven Christenson on Vimeo.