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. You don’t need to get the Advanced Stacker, you can do the Lighten mode stacking with the free TEST Stacker.

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.
  • Plan to edit individual frames to clean them up before creating a final version.

One thought on “Tips for Using Layers for Stacking

  1. Steven Christenson Post author

    In case you’re wondering… the “Statistics” method of doing stacking also uses Layers so it’s also a performance dog compared to the action method. We’ll run a test using the Statistics tool for comparison.


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