Ultimate Landscapes and Moon: Nikon Z8 Pixel-shift and AutoStakkert

I thought that Nikon’s Z8 pixel-shift shooting would be the golden ticket for sharp landscapes, but I was disappointed. Even with no wind, heat-shimmer (unstable atmosphere) ruins the merged pixel-shifted shots.

Nikon’s NX Studio is used to merge the pixel-shifted photographs (I usually combine 16 or 32 shots). For indoor work using a good lens, the resulting resolution is absolutely amazing (180 MP). NX Studio is ‘dumb’, though, when it comes to dealing with any subject movement between shots.

I also found out that photographing the Moon doesn’t work with pixel-shift shooting, even when the Z8 takes the photos at 9 frames per second. Both the atmosphere and the Earth’s rotation spoil the results.

The software I’m going to discuss isn’t limited to the Moon or the planets, although that’s what it was designed for.  It can also help with any distant terrestrial landscape shots, as long as your subject holds still.  The key to sharpness is based on statistics.  Most of the time, details of your subject are in the same location, but with a shimmering atmosphere, sometimes they move a bit.  If you take several shots of the same subject and look for details that are “usually” present in each of the photos, you can combine these shots into a single sharper picture.

If you look close enough, you’ll find that some shots are sharper than others.  The software also recognizes this, and is capable of automatically only selecting the “best” shots it locates in a series (a ‘stack’).

The program I’m going to describe is called “AutoStakkert”, version 4.0.1  for 64-bit Windows.  I’m using it on Windows 11.  It’s available on other operating systems, too.  This free program can be located here.

The programs’ Dutch author is Emil Kraaikamp. Emil has kept up with making this program smarter over the years. I wrote an article about this program several years ago, before pixel-shifting was available, which you can look at here. 

The program hasn’t changed very much over the years, so the old tutorial is still mostly valid.

This new article is only for the very pickiest of photographers, who really, really want to get the sharpest landscapes or moon shots. The AutoStakkert program isn’t for the faint of heart or the lazy people. Bear in mind, though, that it can’t cure a windy day; if leaves are blowing around, then stacking can’t fix that. You can also forget about shots with moving water; it won’t work for those, either.

I converted my raw photos into 16-bit TIF files to use the program, but it accepts a variety of image formats.  It doesn’t accept raw formats, though.

There are many, many options available with this program, but I’ll describe a couple of recipes that work for me.  Keep in mind that the intended users of this program are astronomers, not photographers.

I have had best success when using at least 20 pictures in a stack. Since the Z8 pixel-shift feature can shoot up to 32 frames at a time, this is ideal. I’ve seen extreme examples where users have processed more than 10,000 shots in a stack (frames from a video) with this program!  The more atmospheric shimmer, the more shots you’ll need to counteract that shimmer. The Z8 lets you shoot a series of pixel-shift shots, so you can easily go beyond the 32 limit.

Before I forget to mention it, AutoStakkert can output a ‘sharpened’ photo, but I don’t like the result (totally over-sharpened with haloes).  I use the unsharpened output and post-process it with my favorite photo editor instead.

Finished result, after using AutoStakkert. 500mm PF

The cropped shot above, using the Nikkor 500mm PF f/5.6 looks more like it was taken through a telescope. This is a 13-shot stack, using some of the pixel-shift raw shots from the Z8 after converting them into compressed TIF format. No atmospheric distortion seen here! This shot has received no post-processing.

Same merged 16 shots using NX Studio to make NEFX file: disaster!

The very slight orbital motion of the Moon ruined the pixel-shift merge, even with the shots taken at 9 frames per second (the pixel-shift ‘interval’ was set to zero seconds).

Using the AutoStakkert Program Part 1: the Moon

Run the program “AutoStakkert.exe” as an Administrator (right-mouse click on the file to do this). I believe the program author is from the Netherlands, hence the unusual program name.

This program doesn’t like raw format, so you’ll need to convert your photos into any of a variety of image formats (I use 16-bit tiff with LZW compression).

AutoStakkert: Moon uses “Planet” option, landscape uses “Surface”

For my moon shots, I don’t bother to re-center the moon in the frame to counteract the Earth’s rotation.  The software takes care of that, when you choose the “Planet (COG)” Image Stabilization option. You get the same effect as you would from using a motorized equatorial mount.

If you’re shooting distant landscapes, you need to use the “Surface” Image Stabilization option instead, where your subject isn’t moving. If you don’t use a tripod for this, then you might as well stop reading the article at this point.

The screen shot above shows some of the settings when shooting the Moon. I’ll show an example later that demonstrates some suggested ‘landscape’ settings.

Click the “1) Open” button, and browse to the folder with your (TIF, JPG, etc.) multiple shots to process.  Use the “control” or “shift” buttons to select the desired photos to process as a stack.

Selecting the pixel-shifted files to stack

Review the photos for alignment

Scroll to center your subject in the window before reviewing the shots. The moon, even at 500mm, isn’t very large in the photographs.

After clicking on the “1) Open” button and selecting the 16-bit TIF photos, I click the “Play” button to see if the automatic rough alignment was successful.  This rough alignment counteracts the rotation of the Earth between the shots, assuming you don’t bother to realign the moon in your viewfinder. The “Play” button starts a slide show running. Image quality grading numbers get displayed next to the “F#” (frame number) on the photo-display dialog upper left side. You can click in the “Frames” progress bar to manually step through the image stack, too.

This lets you easily compare how sharp each shot is, relative to each of the other shots.  Click “Stop” to halt the slide show.

If you have selected “Planet (COG)”, the stack of photos should already be roughly aligned with each other. If you set your camera pixel-shift ‘interval’ to 0 seconds, the alignment isn’t much of an issue anyway.

Screen shot after photo stack analysis, before clicking “Place AP grid”.

Click the “2) Analyse” button next.  This will perform an initial quality assessment of the selected pictures, and then decide which are the sharpest photos.  It generates a plot of the shot quality as well. The program will place your shots in order of decreasing sharpness. The gray line in the plot is in the same order as the input photo file stack, and the green line is the sorted order of the frames.

Click on the “Frames” button to switch between sorted or original input frame order, and use the slider to switch from frame-to-frame (or else type in the desired shot number). The “Frames” button turns green when this feature is available. If you place the mouse pointer over the slider area, the tool-tip text will indicate the active sorting order (“The frames are now sorted by quality”).

“Frame” slider/input box to view stack images and their quality rating

Note the “F# below the slider, such as “F#3 [15/16]”, which indicates the 3rd frame of 16 is the fifteenth sharpest photo, and the third shot (file) in the stack. This example frame is in the “top 93.3 % ” of the entire stack, and has a quality rating of  “Q 3.3%”. You generally want a photo quality rating of 50% or better in your final stack. Frame #3 shouldn’t be included in the stacking.

There is a zoom slider and horizontal/vertical sliders to magnify and shift the view of the selected photo in the stack.

This is an under-appreciated program feature.  You might have hundreds of photos, and it would be a terrible chore to manually figure out which ones are the sharpest. This feature automatically finds them and sorts them.

You’ll get an error (!#@Anchor) if your shots aren’t aligned well enough for analysis. You’d probably get this error if you did a whole moon shot but selected “Surface” instead of “Planet (COG)”, and the moon was in a different location in each shot. I presume “!#@Anchor” is some form of Dutch swearing.

Alignment Point setting

If the Analysis looks good (view the graph for a nice continuous plot showing gradual decrease in image quality of the sorted shots), you’re ready to select the final alignment points. For quality ‘planet’ input images, select a “small” alignment point size (AP Size) of 24. For lesser quality images, select a larger number. I have experienced alignment mistakes when using larger alignment point sizes.

I’d suggest you use the automatic alignment point creation, which will put many points on your image.  Lots of points are needed for quality alignment of the shots in the stack. There’s a manual placement option (“Manual Draw” checkbox), although I haven’t had good success with it.  After Analysis, there will be a red rectangle over your displayed photo. If you want to try placing manual alignment points, don’t put any points outside of this rectangle, since some of your shot details go outside of this rectangle.

Place the Aligment grid

Click the “Place AP grid” button next. This is the automatic way to get the alignment point grid added to your displayed photo. This is fast, easy, and lazy, which I’m all for. It will put a grid of points over the entirety of your subject, but avoids the black background (if you’re shooting moon shots).

There’s an “Alignment Points” “Clear” button, if you decide you’re unhappy with your detail selections (and you want to start over). You can try changing the alignment point size, if you wish to experiment with that option.

I have a value of “80” (green box) for the “Frame percentage to stack” in the section labeled “Stack Options”.  This will cause the program to only use the best 80% of the shots in the final processed shot, and it will throw out the worst (most blurred) shots.  Use the “Quality Graph” and “Play” results to help you decide on the percentage of sharp shots you want to retain for the final stacking process.

The “Normalize Stack” option will enforce a consistent brightness level for each shot, and isn’t typically needed unless you have a non-black sky with your moon.

The “Drizzle” option was originally developed for the Hubble telescope. It is intended to take under-sampled data and improve the resolution of the final image. This option doesn’t seem to help my shots any. It will really slow down the stack crunching if you select it.

I selected “TIF” for the output format of the final processed shot (under “Stack Options”), which will be placed in this case into a folder next to your input photos, and called “AS_P80”.  This folder name indicates it was created by AutoStakkert, and has the results of selecting “80 Percent” of the input shots.

I left the “Sharpened” checkbox un-selected and the “Save in Folders” selected. I’m not a fan of the sharpened results from this program, but it can still be a useful evaluation tool, even if it’s not good “art”. You’ll get an extra output file with “_conv” add to its name if you select “Sharpened”.

Notice in the screen shot shown above that the program automatically added 1801 alignment points onto the photo after clicking the “Place AP grid”, and added the text “1801 APs”. When I have used less than 300 points, I have noticed occasional alignment errors in the final results.

Now, click the “3) Stack” button.  And wait. Then, wait some more.

You’ll get some progress messages with little green check marks and how much time each of them took as they complete.  Expect several minutes to elapse before the stacking is complete.  The finished output files will be in TIF format if you matched my TIF output format selection. A fast computer is really handy here. Unfortunately, this program doesn’t take advantage of a GPU to speed things up.

The resulting pictures include an unsharpened image and also a sharpened image (with “_conv” at the end of the file name) if that option was selected. As I mentioned, I don’t like how this program does sharpening, so I would post-process the unsharpened stacking result in another photo editor. The finished result (TIF) file has “_lapl4” and “_ap1801” as a part of the file name, because in this example I used the “Laplace” delta, noise robust 4, and created 1801 alignment points.

Note in the shot above that you can see green checkmarks with timing measurements.  This section gets filled in as the program progresses. Finished results (TIF files here) go into the “AS_P80” folder, since 80% percent was selected for the “Frame percentage”.  If you had chosen 70 percent, you’d have an “AS_P70” folder instead.

You’ll find that the program is smart enough to not only shift your photos for accurate alignment, but it also applies rotation correction!  Impressive. Like I said, this guy’s an astronomer.

Single (unsharpened) shot example crop.  NOT a stacked photo.

The picture above is the best single-shot photo I had to work with, which has not been post processed. It is actually missing some subtle details and also has some ‘false’ details, all due to (minor) atmospheric shimmer. It’s pretty good as-is, but can still stand some improvement. The un-cratered “mare” are particularly noisy and contain some misleading ‘false’ detail. You’ll be doing yourself a favor if you take your photos with the Moon high in the sky, so that you aren’t shooting through as much atmosphere.

Autostakkert final processed shot detail, no sharpening.

The cropped shot above (magnified a few hundred percent) shows the result of using the best 80% of my stack of 16 original shots.  It still needs post-processing for any brightness, contrast, or other alterations.  If I had shot many more photos for the stack, the quality would improve even more. This crop is from the photograph at the top of this article.

If you compare the details between the “single shot” and the finished AutoStakkert stacked result, you can see several extra details that show up in the stacked picture.  Note the smooth surfaces are starting to show subtle shading, which is missing in any of the single shots.

This program really does work. If I had shot many more photos, then the results would improve even more. I’m certainly not an expert at using this program, but it’s clear to me that stacking photos can absolutely increase the level of detail that moon (and general landscape) shots contain.  It’s almost like getting a better lens than you really have.

You could, if you’re inclined to do so, even shoot a movie of your subject (converted to AVI) and Autostakkert can use that as input, too. But this article is about using the pixel-shift feature.

Part 2: Landscapes

If you photograph a distant subject, especially on a warm day, heat shimmer can be severe.  Using the “Surface” option (instead of “Planet”), you can dramatically improve subject detail if you use a tripod and take at least a few dozen shots for stacking.

Distant landscape “Surface”, with many alignment points

The screen shot above shows the selected options for processing a stack of distant (10 km, or about 6 miles!) landscape ‘Surface’ shots. Unlike moon shots, you must keep your subject framed exactly the same shot-to-shot for “Surface” processing. If you look carefully, you’ll notice that the auto-alignment grid shows 58574 points (!).

Notice that I set the “AP Size” to 48 instead of the 24 used with the Moon. It placed the alignment points all over the photo, except in the places that were really out of focus, after clicking the Place AP grid.

Just like moon shots, you can “Play” the stack of frames to evaluate sharpness and alignment.  Try to stack only the frames that have a quality rating of 50% or better, and rid any frames that don’t align well relative to their neighboring frames.

Mid-stacking progress screen, using 60% of 32 photos

Stacking has finished (16-shot example) with 58,574 alignment points

Stacking has finished (32-shot example) with 60,410 alignment points

My best single RAW shot in the stack, 100% magnification

Plenty of shimmering air turbulence here. The antenna structures are really distorted.

Antenna detail, single RAW (NEF) shot

Pixel-shifted NEFX merged 16 shots, NX Studio

The NX Studio merged picture looks a bit better than the raw shot in this case (many times it’s actually worse), but details are fuzzy.

NEFX ‘merged’ shot detail

AutoStakkert from 16-shot pixel-shift tif photos, 60% used

All of the details are a bit clearer than the NEFX results. Using only 60% of 16 shots is about the minimum number you should use for this program. More is better.

AutoStakkert 16 shot series detail

AutoStakkert from 32-shot pixel-shift tif photos, 60% used

AutoStakkert 32 shot series detail

The more shots you use, the better the results using AutoStakkert. You can always make a series of pixel-shifted photos, if you want to get the results even sharper.

The sharpness differences aren’t vast, but you do get better resolution using AutoStakkert, and the sharpness increases with more shots taken.

Conclusion

If you’ve got the time and motivation to get the very best out of your gear, then give this program a try.  You might just find AutoStakkert becoming a welcome part of your tool kit.  If you’d like to read more explanations of this software, here’s a handy link .

This program does a superior job at handling pixel-shifted shots when compared to the Nikon NX Studio, although it’s definitely slower and much more difficult to use.

Once again, photos and science make a perfect blend for your art. Thank you so much, Emil Kraaikamp!