Blog

Vortex star trails tutorial

14Mar
  • Vortex star trails tutorial

When I made this photo I never imagined it might become as popular as it did since it doesn’t have that much of a foreground, but I underestimated the curiosity from the community on how I processed my photos to make the “vortex” or “zoom” effect, so I decided to write this small “vortex star trails tutorial” on how I did it. It is not an easy or entry level tutorial and I’m aware there might be a lot of other ways to achieve this same result but this was the best way I’ve found so far, so I hope you enjoy it and if you do please share your photos with me so I can see what you come up with.

First of all, I believe in giving credit where credit is due so I must start by saying that I was inspired by the work of Lincoln Harrison. He was the first photographer that I saw doing this kind of trails, and I’ve been intrigued and inspired by them for the longest time. Although his work is different from mine in the sense that he does it in the field (using a custom zooming mechanism) and I am doing it in post production emulating that zoom; I still think I need to thank him for coming up with the idea.

ZOOM! That’s all there is to it. Just need to simulate that you’re zooming out of the frame and that along with the natural movement of the earth will make your star trails look like a spiral rather than a circle. To illustrate, here’s an example of how the trails would have looked like without doing the zoom technique:

Basic star trails Basic star trails without the “zoom” or “vortex” technique

The question is, how do you emulate the zoom-out? I used Adobe Lightroom with a tool called LRTimelapse (which is a great tool for doing time-lapse videos out of your photos), but I do have an alternate option if you don’t want to use LRTimeLapse which I’m describing at the bottom of the page.

I will not go into much detail on how to use LRTimeLapse (there is a great level of documentation about it on their site); but the main thing I did was to define two keyframes, one at the beginning and one at the end. Once I was back in Lightroom, I modified the crop for my first photo to be the “zoomed in” frame, and I modified the last photo to be the “zoomed out” frame. The image below represents the crop for my first photo:

Lightroom crop Using the crop tool in Adobe Lightroom to set the initial crop

A couple of tips that might come handy for cropping are:

  • In order to show the dimensions for your photo, you just need to hit the “i” key while you’re in the Develop module. This can help you define the final resolution for your photo (since the first crop will define the maximum dimensions of your photo).
  • I strongly suggest keeping the lock in the aspect ratio section in Lightroom. If your photos don’t have a consistent aspect ratio LRTimeLapse might throw an error message and your end photo might not match properly.
  • If you hold the Alt key (Option in mac) while cropping your photo, it will crop from the center which might make it easier to keep a consistent size.

Afterwards, you just need to save the metadata from your keyframes to disk, reload the photos in LRTimeLapse and have it make an “Auto-transition”. This will change the crop settings in all the photos between your two keyframes and will make a smooth animation from start to end.

After saving the metadata to file in LRTimeLapse, all that it is left to do is reload the whole sequence in Lightroom and export your photos, keeping in mind you need to set it to resize the image to fit the shortest edge to the shortest edge from your first crop (in my example above, that would be 2,734 pixels); and then just process the photos using your method of choice for star trails.

Export rezise

The resulting video from LRTimeLapse is below, and while it doesn’t look like much by itself, it did help achieve the start trails image:

Now, I suggest using LRTimeLapse to make your life easier (and because it’s a great tool!), but if you don’t want to spend the extra money or if you like scripting, math and would rather doing it by hand the principle is the same: In Lightroom, adjust the end crop for ALL your photos and save the metadata to files; then, adjust the crop of your first photo to have the desired settings, and save that metadata to file.

Afterwards you would need to open the metadata files (they should have the same name as your RAW files, with an .XMP extension) and look for the following fields:

<crs:CropTop>0.1</crs:CropTop>
<crs:CropLeft>0.2</crs:CropLeft>
<crs:CropBottom>0.1</crs:CropBottom>
<crs:CropRight>0.2</crs:CropRight>
<crs:CropAngle>0.0</crs:CropAngle>
<crs:CropConstrainToWarp>0</crs:CropConstrainToWarp>
<crs:HasCrop>True</crs:HasCrop>

If you don’t see them, you might have not done a crop to all the photos (if you want your end photo to be the complete “zoom-out” you will need to crop just a bit for Lightroom to save the crop tags to file).

Once you have that, just get the difference in crop from your first photo to the last photo, divide that by the number of total photos you want to have, and then just add that factor to the crop in every photo (incrementally of course). Once you’re done, reload the metadata in Lightroom and you should be set.

One thing to keep in mind is that not all compositions will work with this kind of technique, and that any foreground elements will be affected by the zoom, so some masking might be necessary, or you might need to do a composite . In my resulting photo I needed to mask the tree from my last frame so it wouldn’t look all blurry.

* I am using Lightroom 5 and LRTimeLapse 3, so I’m citing the examples using these tools. You might see different results or different values if you’re using a different version.

If you do decide to use LRTimeLapse, using the links in my page before buying your license would help support my blog :)

UPDATE JUL-07-2014: After tinkering some more with Adobe After Effects I believe the same results can be achieved by doing the zoom in AE and then exporting the image sequence. Let me know in the comments if you’re interested in me doing a tutorial with that process and I’ll try doing a new tutorial for it.

Comments

Leave a Reply

%d bloggers like this: