Tag Archives: Star Trails

Warning: That RAW image is not really RAW – and why it matters

Confusion Abounds

Unfortunately it is quite complicated to remove the default Camera Raw adjustments due to conflicting details on web sites, including on Adobe’s own FAQ. As my experiments show, the “default” settings for ACR apply adjustments. Adobe says that using CTRL-R (CMD-R on a Mac) resets to the defaults for a RAW file, but it doesn’t reset everything because the default settings do have adjustments! Below are the choices for selecting, saving and resetting Camera Raw Defaults – you find this menu in the upper right of the ACR display – see more illustrations below.

In my tests with ACR 7.0 CTRL-R – which theoretically is the same operation as selecting Camera Raw Defaults – did not remove hand applied adjustments to clarity, tint, noise reduction, sharpening, vibration or saturation, tone curve, and other settings. What CTRL-R actually does is remove adjustments to Exposure, Contrast, Highlights, Shadows, Whites, and Blacks. Using the Camera Raw Defaults (first highlighted choice in the list above) doesn’t get what you might expect! So I went further. I set all the values to zero, then used Save Camera Raw Defaults, selected Camera Raw Defaults for the image and opened it using the Open Object button. When you use Open Object ACR creates a .XMP file – sometimes called a sidecar file – that I inspected to see what has been set. The non-zero settings in the XMP file after saving my custom camera raw defaults and choosing Camera Raw Defaults included the following non-zero settings:

 crs:Shadows="5"
 crs:Brightness="+50"
 crs:Contrast="+25"
 crs:ParametricShadowSplit="25"
 crs:ParametricMidtoneSplit="50"
 crs:ParametricHighlightSplit="75"
 crs:SharpenRadius="+0.5"
 crs:LensProfileEnable="1"
 crs:AutoLateralCA="1"
 crs:CameraProfile="Camera Faithful"
 crs:LensProfileSetup="Auto"
 crs:HasSettings="True"
 crs:HasCrop="False"
 crs:AlreadyApplied="False"

When I saved my own Camera Raw Defaults I turned on Chromatic Aberration and Lens Profile correction and overrode the white balance to “Camera Faithful” just to be sure that the new Defaults were actually using my saved default settings. But wait! There are still Brightness and Contrast adjustments listed even though I had set those values to zero. It is also not clear whether it is applying a tone curve adjustment. The good news is that my saved defaults are NOT doing any sharpening or noise reduction whereas the ACR defaults (the default defaults?) do mess with those.

Further Experiments

Before I tried to set my own Camera Raw Defaults, I followed advice I found online. That is how I discovered that the default, Default Camera Raw settings include both sharpening and color noise reduction.

Using the “Camera RAW Default” selection from the menu. Some changes are still being applied!

Notice how the settings file (XMP) contains adjustments for color noise reduction, a tone curve, and sharpening. The real head scratcher is that the side-car (XMP) file also shows adjustments to Shadows, Brightness and Contrast – which are NOT shown on the Basic (leftmost) settings panel for the image. Not knowing the internals of Photoshop, I can not tell if the brightness, shadow and contrast adjustments are actually present or not.

The XMP file and the display do not agree.

Basic does not show adjustments that are in the XMP file!

Unfortunately there are sites that claim that using the CTRL-U (CMD-U) sets all the values to default. This is incorrect. CTRL-U toggles between automatic and not automatic which is the clickable text Auto in the settings dialog. What I’ve called Default RAW Adjustments in my comparison photo at the top of this article is actually automatic adjustment – I was mislead! What is automatic? It is a roulette wheel whereby you let ACR take its best guess at what it thinks will look right. Apparently it is pretty smart unless you let ACR do its automatic thing on a night image in which case the result will not be very pleasing.

The stated Adobe method to reset to Camera Raw Defaults is to use CTRL-R (CMD-R on Mac). After using this magic sequence I see that there is still sharpening, a tone curve and much more.

Confused?

Yeah, me too.

In fact, the default RAW setting can be per camera per ISO. The bottom line for me is that I do not trust ACR to not mess with my image unless I apply a Linear “Develop Settings” to all the images I’m going to load. And I am not even sure that some adjustments are not still being made despite my strong desire to have my images be unfooled around with.

But Why Do I Care?

A RAW file that has nether been sharpened nor had a tone curve applied looks flat and boringish. Why so boring? A digital camera records images in a linear fashion but our eyes don’t perceive things that way. To prevent people from squawking, ACR by default applies tonal adjustments to convert the raw data into something more adapted to what we see.

Of course you might ask why anyone would ever want to look at the un-adjusted image, and the answer is I wouldn’t want to either… but when stacking the fact that the pixels haven’t been diddled with beforehand makes the result better.

How do you get really RAW Raw Images?

For starters, you can set all of your Raw Defaults to Zero and save them as I noted in the Confusion Abounds section above. As a further belt-and-suspenders technique I also created a preset called “Linear” using the Save Settings menu. I apply the “Linear” preset to my images before I open them to force the sidecar files to be created. Whether ACR is still messing with some of the data is not clear.

But what about Cooked Images?

I don’t always go “really RAW” – I may tweak the settings in ACR for a more pleasing visual appeal. The literature indicates that ACR is a bit better at making adjustments than Photoshop is. The good news is that you can have your cake and eat it too because no matter what you do in ACR it does not change the data – just the adjustments that are applied to that data.

Here is how I made adjustments to the same image shown earlier along with all the non-zero values from the .XMP (sidecar file).

So if RAW is so Complicated I Should Stick to JPEGS, right?

Heavens no! If you shoot JPEGS rather than Raw you’re throwing away a lot of good data. The processing to convert the captured data into a JPEG involves lots of decisions made on your behalf, behind your back, and without the ability to change your mind later. Yes, you can diddle with the image, but you will not get the results you might if you had not let that little conversion monster distort your pristine data. In other words, you’ll eventually regret what happened.

More Star Stacking Tricks: Use the Bridge

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Perhaps the most popular thing we’ve done at StarCircleAcademy is to provide a stacking action for Photoshop. What can you do with it? Alas, you can’t use it to end hunger, or create world peace. However, the action allows you to automate the task of creating star trails from individual images. You can create the trails from JPGs, TIFFs, or even RAW files in fact from any file that Photoshop is able to load.

You have to capture the images in the first place, so we humbly suggest you begin with understanding How to expose, how to shoot, what settings to use, and even what to consider to create a more compelling image. Or if this is all new, start at the beginning and learn about night exposures and the kinds of star shots that are possible.

Curious about the circle? It is formed by shooting north in the Northern latitudes.

If you have already used the Stacking Action as we previously described you are all set to put on your big-boy pants and do more advanced stacking tricks using, of all things, the lowly Adobe Bridge. Bridge is a lighter weight version of Lightroom (sort of) and it comes with Photoshop and other Adobe products for no extra fee.

Why would you want to use Adobe Bridge as the front end?

Bridge allows you to do mass corrections to raw files before they are used by Photoshop. Anything that Adobe Camera Raw can do, Bridge can do to a number of files all at once.
Bridge has an operation called, uhm, “Stacking” which is a way to group images together in a nice memorable way.
Bridge allows you to SEE and select specific files to operate upon – unlike the “folder” method you may have been using previously.
Bridge is relatively lightweight and doesn’t need preloading as Lightroom does.

It is slightly more complicated to use Bridge for stacking, but do not worry. We will make it as simple as possible.

Suppose you have a number of files to stack and they are located in a single directory along with a number of files that you don’t want to stack. Below I’ve navigated to a big directory full of CR2 (Canon Raw Files) and I’ve used the Ctl Key to select the first four images of a star trail sequence.

As is my customary practice I used a number of colors and lighting methods to begin my star trail and I can tell I don’t like C_066715 or C_066716 (which is too green). So instead I’ll start with image C_066717.CR2. Scanning forward, the clouds start to become a problem by image C_066739 so I have picked images 717 through 738. I won’t be describing how to use it here, but if you look on the lower left side of the Adobe Bridge screen there is a “Filter” window where you can choose images based on ISO, exposure time, keywords, etc. That may come in handy if you want to only select the 24 second exposures in a sequence.

Getting back to my quest… Though I don’t have to, I will mark the images I’ve selected as a stack. NOTE: Images can only be in one stack.

And then I will select ONE of the images to decide what “develop settings” to apply. That is, what to do with the image before stacking it.

Here is where I’ll give you a hint to keep you from banging your head on the wall. If you click the “image” of the stack you will only select the first image. However if you click on the count of images (where the yellow arrow points) it will select the whole stack. Here I’m selecting only the first image by double clicking it. My primary interest is getting the color balance about right. There are lots of ways to adjust the white balance including using the white balance tool or adjusting the color temperature. This is also a potential departure point because there are two ways I might want to address my set of images:

I may want a nice clean star trail with gaps as small as possible, OR
I may want to produce individual frames for an animation or timelapse.

If my goal is a star trail, then I will set all of the sliders to zero, set noise reduction to zero, and set the curve to “linear”. About the only thing I’m likely to do is vignette correction – leave lens correction for later, it may cause bad things. In fact, I have created an ACR preset to do exactly that I call it “linear”. If, however, my goal is a timelapse, I’ll try to beautify the image as much as possible including sharpening, noise reduction, and exposure corrections.

For this example, I am taking the beauty route. I made the adjustments I want and saved the settings as a preset called “TronaStack”. Next I will apply those settings to all of the images in my stack. What really happens is that Adobe Bridge creates sidecar (XMP) files for each of the images and re-renders the file in Bridge to approximate the changes.

Mass Applying Settings

With all the raw settings applied, I want to do the stacking operations exactly as described here – but we will be using “Bridge” as the source.

NOTE: Your menu might look a little different especially if you haven’t installed Dr. Brown’s Services. As you might have guessed, using “Photoshop -> Batch” invokes Photoshop. The next screen you see will look familiar except you’ll notice the Source is Bridge.

As the instructions state, you should run the “Do This First” operation. It creates a properly sized black background using the dimensions of the first photo in the stack. You then re-run it with the operation you want. Here I’m using the comet stacking option of the Advanced Stacker. It is important to make note of the output options. If you don’t override them, the intermediate result will be written over itself repeatedly.

The Advanced StarCircleAcademy Stacking actions will create “Comet_” documents but you’ll need to add a unique number as shown above. If you don’t like the base name, you can substitute whatever you like instead of “Document Name” above. E.g. “MySequence”. I often set the starting serial number to the first image number in the stack since I try to make sure I uniquely number every image I capture.

After stacking the output appears in the “C:\tmp\StackTest” folder like this:

What is especially cool is that I’ve directly stacked the RAW files into “comets” for an animated sequence. I could then create a timelapse out of those images if I wish. Of course there is one hitch. The huge files are too large to easily create a meaningful timelapse. It would be so much nicer if all the images were straightened, downsized and cropped to a specific format like 1920 x 1080 (HD) or 800 x 600. That is a topic for another column, but Adobe Camera Raw can do the trick. And it’s also possible to do the deed with the Advanced Stacking action.

If you’re wondering how you can get your hands on the Advanced Stacking Action with comets and more see the Store.

Can I Use Mini Bridge?

Well, yes, you can, though Mini Bridge only works if Bridge is open so it’s not really very mini!

Advanced Star Trail Tricks

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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:

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.
Blobulous – stars at the beginning (or end) of a trail are made to stand out from the rest of the trail.
Comets – star trails appear to grow brighter and the end of the trail looks like the nucleus of a comet.
Streakers – Like comet only the trails are longer
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.

Smoothee

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.

Blobulous

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:

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

Settings

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.

If You Want a Better Star Trail…

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Tag Archives: Star Trails

Warning: That RAW image is not really RAW – and why it matters

Confusion Abounds

Further Experiments

Confused?

But Why Do I Care?

How do you get really RAW Raw Images?

But what about Cooked Images?

So if RAW is so Complicated I Should Stick to JPEGS, right?

More Star Stacking Tricks: Use the Bridge

Mass Applying Settings

Can I Use Mini Bridge?

Advanced Star Trail Tricks

Building Blocks

Smoothee

Blobulous

Comets and Streakers

Settings

If You Want a Better Star Trail…

Confusion Abounds

Further Experiments

Confused?

But Why Do I Care?

How do you get really RAW Raw Images?

But what about Cooked Images?

So if RAW is so Complicated I Should Stick to JPEGS, right?

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Mass Applying Settings

Can I Use Mini Bridge?

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Building Blocks

Smoothee

Blobulous

Comets and Streakers

Settings

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