Tag Archives: Picasa

Star Trail Creation – Step By Step

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Originally Published: November 19, 2012
Last Revised: March 3, 2017

I dredged this one up out of the archives. Many people ask me “how do you do those star trails, Steven.”  If you want a grand overview of the process, my Treatise on Star Trails is a good read. However here I reveal step-by-step how I create a star trail image from the first shots to the finished image. The method shown below is for creating simple (lighten mode) star trails. If you want to do some fancy effects, please take a look at our Advanced Stacker Plus.

Here we go.

South Side [C_009842-75br]

Photo 1: Quickly stacked image which is a composite of thirty-three 6-minute 500 ISO exposures and one 30 second, ISO 2000 exposure.

The above is my first quick attempt at creating a star trail, and following is summary of how I created it.

It starts with the test image and continues with the exposure set. For background on how to navigate the various shooting choices, see: the summary Stacker’s Checklist. The theory about selecting exposures may help.  And there is a two-part series that addresses the difficulties you may encounter. See Part 1 and Part 2. If you’re curious how I get the stars to form circles, this article will provide the information.

I usually start with a short (30 second or less), high ISO exposure to gauge several things: 1. How well framed my subject is, 2. How sharp the focus is, and 3. What I may need to adjust to control the sky-glow.

Photo 2: First, image: ISO 2000, f/2.8, 30 seconds.

After taking the first image, I realized two things: one is that the trucks passing were providing helpful light on my foreground – but not always illuminating the entire thing.  The other is that the exposure (ISO 2000, f/2.8, 30 seconds) was under exposed.  I needed to at least double the exposure to 1 minute. Let me stop for a moment. Those of you who don’t do much night photography are thinking “Whoa from 30 seconds to 1 minute is a huge difference.”  But no, it’s not. It’s only one f-stop. It is no different from changing a daylight exposure from 1/200 of a second to 1/100 of a second.

Starting with an exposure at 1 minute, 2000 ISO f/2.8 as a starting point I calculated an  ISO 500, 6 minute exposures at f/3.5. Here is how: A 1 minute exposure at ISO 2000 is equivalent to a 4 minute exposure at ISO 500 (500 is 1/4 of 2000).  Changing the aperture from f/2.8 to f/3.5 drops the light by about 33%, so I increased the exposure from 4 to 6 minutes.

I set my camera to record in RAW and my interval timer to take 5 minute, 59 second exposures every 6 minutes. I pulled out my reclining beach chair, a sleeping bag and slept while the camera clicked.  Below are a few of the shots. Note how the light changes from passing trucks!  You can also see the counter-clockwise rotation of the Milky Way. The last shot was taken as twilight approached is too bright to use because the sky is losing contrast and the light on the cliff is looking flat. I did not include that last shot in the stack.

Photo 3: Collage of some of the photos used in the stack.

I downloaded all the images from my card to my Incoming folder which is organized by date.  I used Digital Photo Professional to pull up the images, applied a bit of contrast enhancement, a slight exposure increase (1/3 of an f-stop), and a very slight noise control over the entire image. I exported in Landscape style which adds a slight saturation increase (Photoshop Saturation and Vividness) and modest sharpening. I cloned the recipe to all the photos and exported them into a “RedRockEast” folder in a temporary directory.  I could have done all these things with ACR (Adobe Camera Raw) or Lightroom.  In this case I didn’t have to do any white balance adjustments because I had preset the camera to approximately 4100K.

I then dragged and dropped all the exported (JPG) images onto Image Stacker which took about 3 seconds per image – less than two minutes to create a result. My option for Image Stacker was “Brighten” mode. I could have used the Star Circle Academy Stacking Action in Photoshop instead and the result would have been identical.  The stacking action takes about the same amount of time, but is more versatile and can even use raw images. (Note: StarStax is a program that supports Mac, Unix and Windows and works well, too!)

Photo 4: First Results stacking 34 images in Image Stacker by Tawbaware – this is effectively a 3 hour, 24 minute exposure.

The result was a little dark and flat so I used Picasa 3 to increase the exposure (called Fill Light), highlights and shadows – each by about 1/4 of the scale, and I warmed the photo by slightly tweaking the white balance (Color Temperature). That was all I needed to get the image shown in Photo 1.

Screen Shot 1: Picasa Adjustments

One obvious problem with the result is that the combination of the early short exposure with the sequence of shots left a gap. There really was no reason to include the first shot.

I want the cliff to pop a bit better, so my next course of action was to work on improving the foreground.  I found all the brightest shots of the cliff face (e.g. when the trucks were lighting them), and combined them using additive stacking to brighten them and averaging to reduce the noise. Remember that “brighten mode” (Lighten in Photoshop) does not brighten anything – what it actually does is select the brightest pixels at each location from each of the images in the stack.  The brightest pixels may also be noise! Using averaging reduces the noise significantly – but it will not remove “hot” pixels; we will address those later.  Fortunately Image Stacker has an option to stack and average. All you need do is specify the divisor.  If you have 10 images and specify a divisor of 10 then you are simply averaging. But if you specify a divisor of, say 5, then you are averaging AND effectively increasing the brightness by about 1 stop.  I used 12 images and a divisor of 3. And I made the same adjustment to the result in Picasa as I showed in Screen Shot 1. But I wasn’t happy with the result – the foreground still wasn’t bright enough.

Next I took 10 of the brightest images and Stacked them (additive).  After tweaking shadows and brightness in Picasa I got this:

Photo 4: Additive stack of 10 images.

Now my foreground is better, but I have created a new problem. The sky is over-bright and the hot pixels and the noise are significant as shown in a 100% crop below.

Screen Shot 2: 100% view showing Hot Pixels and noise (white speckles)

The hot pixels here have a purple fringe to them. Sometimes hot pixels are tinged red, green, blue, white or gray. I will fix hot pixels in my next to last step using the clone stamp (Picasa’s retouch) or the healing brush in Photoshop.

While the noise is obvious at 100% I think it will be fine so I am not going to address it.  If I later find the noise intolerable I will go back and stack more images and average them. Or I may return to the original images and apply stronger noise reduction in Digital Photo Professional and re-export them.

My next task is to remove the over-bright sky from the Photo 4, above. Sky removal is rather easy with the wand selection tool in Photoshop. I select all the sky and fill with black after making a few more tweaks to contrast and color.

Photo 5: Sky removed and replaced with black.

Since I now have a black sky version with the foreground as I like it, I can include this frame in any other stacks I make, and my foreground will be just as I want it. If I were working entirely in Photoshop, I would not have to fill with black, I could just use the result as a layer with only the foreground revealed by a mask.

To complete the process, I restacked 33 images together with the sky-less foreground image (Photo 5). Some more minor shadow and color temperature tweaks and some spot corrections of the few hot pixels (there were about 15), an addition of my copyright and this is the result:

Photo 6: Final Image

Since I had all the images for the stack, I was challenged on Flickr to also make a time-lapse video. This video below also helps to illustrate how stacking works. I collected the original thirty-three 6 minute exposures and cropped them to HD format (1920 x 1080). I then created and a sequence of stacked images using the intermediates option of Star Circle Academy Stacking action and joined them into an animation complete with a lovely snippet of the song Kidstuff by Acoustic Alchemy. In my next column, I’ll show how to create the time-lapse animation.

Red Rock Dancing *Explored 03-03-2011*

If you would like hands on experience and instruction, you can join us at a StarCircleAcademy Workshop

Creating a Timelapse Animation Part 2 of 2

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Foundations

Hopefully you’ve already read Part 1 of this column where we showed how to get started with a timelapse animation: choosing exposures, frame rates, etc. Now we’ll get to the good stuff and show several techniques for animating the resulting star shots.

Simple Timelapse – Picasa Movie Maker Option

To do a simple animation using Picasa (free tool from Google) here is how you go about it. Organize all of your identically sized and processed frames into either a single folder or a Picasa Album.

Illustration 1: Picasa with a set of images captured in an Album. Would work the same if a directory were used.

Select the Album (or directory) and click the Movie option.  You’ll get a default title screen.

Illustration 2: The Movie Creation Option of Picasa

Click the “Movie” tab, and change the transition style to “Time Lapse”. Set the slider to 1/10th Sec (or shorter if you wish) and click “Create Movie”.  After a short while you might have something like this:

Now that was simple!

Getting More Advanced – Titling, Credits, and Sound

The Titling and “Slide” options of Picasa are rather limited, so I prefer to add my own titling.  Here’s how:

  1. If still in “Movie” mode select “Clips” then “Get More” which returns you to the “Library” mode.
  2. Select the slide to use for your Title – e.g. the first, last, a composite, or something altogether different. Make sure it’s the same size as your time lapse.  I usually use the first or last slide and use “File -> Save a Copy”.
  3. Load the desired slide.
  4. Use the Text Tool in Picasa to add the text you like sized, angled and colored as you please.
  5. You can animate the title by changing colors, and other effects, but don’t go overboard just yet – as this is not a very efficient way to create titles!
  6. Duplicate the title slide “File -> Save a Copy”.  For each second you want the text to appear you’ll need to have enough frames. So, for example for a 1 second appearance at 1/10th of  a second duration, you need 10 frames.
  7. NOTE: If you want to make the text appear for 5 seconds, you don’t need to make 50 frames, you can make 10 or fewer and reuse them (see step 9 below).
  8. In this example I used the first frame, added my text and saved it 6 times (File -> Save a Copy).
  9. I selected the 6 identical title frames, and clicked “Back to Movie Maker” at the bottom.
  10. I made sure the movie was at the beginning by dragging the slider beneath the window all the way to the left.
  11. Next I drag my “clips” onto the beginning of the movie.
  12. If I need more title frames, I select “Get More”, reselect the same slides and repeat step 11 until happy.
  13. Credits/closing titling can be done the same way as the titles.

After adding credits, and a “The End” (animated in color!) final slide set my movie now looks like this:

Oh, and I added music too. Any MP3 file should work. Just use the “Audio Track” option to load it.  If you want to start the music at a particular point and do fade in, fade out, or cross fade different audio tracks Picasa is not the tool for you.

NOTE: When you add an audio track, be careful that you also have the “Truncate Audio” selected or Picasa will want to extend your movie for the length of the song. You might also need to change the slide duration to your desired speed. Picasa Movie Maker has a bug where it sometimes resets the speed to 24 frames a second (as it did above – did you notice how much faster the newer version was?!)

Getting Even Fancier

What if you want to do something really cool like have the star trails “grow” (or shrink)? Well we’ve got you covered there, too!  Hopefully you’re already familiar with the StarCircleAcademy Stacking Action – if not, give this a read.  We don’t tell you in that blog article, but there is an option available in the Stacking Action (Version 5) to “Stack in LIGHTEN mode creating intermediates“. What that does is super cool. Each time it adds a new frame to the stack, it saves the current results with a unique file name. The final frame is the same as the “Load and Stack in LIGHTEN mode” but every frame along the way is squirreled away where you specify. You can then animate those just as described above. Here is a simple example:

A more interesting example shows what happens when I start the animation near the middle. I then stack ten frames at a time (using Image Stacker) and animate them. I then stack the stacks of 10 into stacks of 50 (which makes it look like it’s moving faster) and finally I then repeat all the frames from beginning to end. It LOOKS like the movie is getting brighter but what is really happening is you are seeing the moon rise!

For another similar example, take a look at this. Be patient though as the good part is toward the end.

If you have only a few frames, you can use other modes to create your timelapse, for example this one uses “cut” mode with photos every 1 second.

If you want to go even farther, there are still more free tools that you can use, like Windows Live Movie.  With Windows Live Movie you can do more advanced titling, have music that fades in and out (only one track at a time, however), and more.

Here is an example using Window Live Movie together with YouTube’s annotation options:

Action! Creating a Timelapse Animation (Part 1 of 2)

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One of the nice little benefits of using the stacking technique to create star trails is  that you can take those many frames and animate them.  My first foray into animation looked like this:

“Star Races” was created using the stacking features of StarTrails.exe (Windows program) and composed into a movie using the “Animation Feature” of that same tool. The vertical format works well with the portrait mode images. This video contains no music or titling as those are not supported by StarTrails.exe.  I will cover the technique to create this in Part 2.

A more elaborate effort with music, stacking and credits is this one created from 8 hours worth of images using the tool Picasa which is free and available for windows and mac:

Not all time-lapses need be created from night images, however. An early example of a daylight animation chronicles my son scaling a rock in Zion. I later did a similar animation using a tripod. The method used to create the animation will depend on the number of frames available and the intent. Let me start at the beginning however.

Shooting Time Lapses

A time lapse requires “frames” – individual pictures used to create the end result.  Usually pictures used to create a time-lapse will be at relatively low resolution (1920 x 1080 or smaller) so shooting them in large format, RAW means extra work will be required to assemble them.  On the other hand, my time-lapse are byproducts of my star trail shots and I always shoot those in maximum sized RAW mode.  An important consideration is the frame rate – that is the number of images shown per second. A movie typically consists of 30 frames per second, so to shoot 5 minutes of video one needs 30 frames per second for 60 seconds x 5 minutes. 30 x 60 x 5 = 9,000 images. Yes, that is a LOT!  However often a frame rate of 10-per-second is acceptable, so only 3,000 images are needed – still quite a lot.  Perhaps we shall start a little less ambitiously and collect 300 frames – enough for a 30 second animation at 10 frames per second. Assuming we are shooting these at night with 2 minutes each exposure it will take 600 minutes (a mere ten hours!). If that still seems like too much work, we can settle on shooting 1 minute exposures and have the shooting done in a 5 hours.  Clearly patience is required. Unfortunately when shooting the night sky it is unrealistic to expect exposures to take less than about 10 seconds even at high ISO.

The software used to assemble the video may also impose limitations. For example in Picasa’s time-lapse mode the minimum frame rate is 6 per second and the maximum is 24. In “Dissolve” or “Cut” mode, the minimum is 1 per second.  The Zion climbing shot is done in Dissolve mode.

Animation Software

Lots of tools exist for this. I’ve already mentioned Startrails.exe and Picasa (Mac or PC), but there is also Windows Live Movie Maker. Each of these tools is free!  Windows Live Movie Maker is the most versatile free tool I have tried with titling and transition options.

Non-free tools for the PC include Adobe Photoshop, Adobe Lightroom, Adobe Premiere. For the Mac there are iLife (iMovie), Final Cut Pro, and many others.

Music, Copyrights and Credits

While a simple time-lapse may be interesting adding music makes it more so. The free tools support music in some (small) fashion but sometimes just barely. Picasa for example will let you select an MP3 song. Unfortunately when creating a time-lapse it will not let you select where to start in the song and does not fade in or fade out – and only one track is allowed.  If you really feel ambitious you can use iTunes to create a segment of a song to include.   Search Google for “creating ringtones in iTunes” (which will help you figure out how to create a snippet), and “export iTunes as mp3”. Creating a snippet using iTunes is not particularly easy, fast or convenient, but it is free – and as a bonus you will discover that you have been wasting money paying for ringtones!

Copyrights and credits can be done in several ways. Live Movie Maker is actually pretty easy to use and allows different text effects. In Picasa you can use captioning (which is only modestly useful for a time-lapse) or text overlays using the Text Tool. The Text Tool is the most versatile but unfortunately in Picasa you can not say “repeat this frame for 5 seconds”, you have to make 5 seconds worth of frames from one image, or keep adding the one image into the movie. If your frame rate is 20 frames per second, you will have to make, gulp, 100 frames for that 5 seconds of copyright or credit!

Creating the Animation

In the next installments, we will show how to use Picasa from beginning to create a time-lapse with music, titles, and credits.

The first 180 images used in the time-lapse are these:

180 of the 675 frames used for the animation

While the title and credit frames looked like this

Title and Credit Frames