Time Stacking 101

April 13, 2014  •  Leave a Comment

NOTE: before reading this tutorial, you should already posses a basic understanding of Adobe Photoshop. I use the latest version of PS, but this technique works with almost all versions.

Equipment Required:
DSLR and appropriate lens (duh!)
Tripod
Intervalometer
Photoshop

For some of us, stacking images is a common occurrence. For others, this entire concept may be new. Most of us who do stack images usually stack photos containing stars, trying to capture what is known as “Star Trails.”

Recently I came across another use for stacking a ton of images into a single shot. A fellow photographer explored the idea of stacking images of daytime shots in order to capture movement. I attempted to achieve this surrealistic and artistic concept, but failed the first couple of times I tried. However, after speaking with the photographer that inspired me to attempt this new concept, and with some additional experimentation, I have finally nailed down the process (although perfecting it is still a work in progress).

Time stack image taken at Sunset Cliffs - 160+ images.

Time stack image taken at Sunset Cliffs – 160+ images.

The above image is an example of the results that can be achieved with this technique. In the next few paragraphs I will give you examples on how to shoot for this affect, as well as the post processing techniques required for stacking and merging the final result.

 

One of the reasons my first few attempts didn’t pan out is because I almost always use manual mode when shooting. So naturally I had my camera setup for a beautiful sunset shot, on manual mode, and I set my exposure to expose the clouds perfectly (the foreground I really didn’t care about). However, I did not take into account that (of course) as my shutter kept clicking, then sky kept getting darker and darker. When all was said and done, my last time stack was a flop because of the gradation in light between the stacked images.

Based off the above, STEP 1.  (and probably the most important) is to use Aperture or Shutter Priority Mode! You need consistent and even lighting for all of the images in order to get a decent time stack. When you set your camera to Aperture Priority mode you’ll notice that your histogram will stay the same (about) even as the sun sets behind the horizon. You’ll notice that as the sun sets your exposures will get longer and longer.

Step 2. Setup your gear, compose your shot, take a couple test shots (if need be) to see if you like the composition.
This is probably the most basic and fundamental parts of the processes, but let’s be honest, if you don’t have a good composition, it doesn’t really matter how spectacular your clouds turn out… Composition is one of the keys to great photography…

Step 3. The next important thing to remember is to ALWAYS expose for the clouds. This will most likely make your foreground dark (unless you’re shooting at noon, but even then the foreground will most likely be underexposed) so you need to do one or two exposures for the foreground (I guess that last bit would be step 3.5…).  This step is optional though (exposing the foreground) and is completely dependent upon your own artistic ideas.

This is the foreground exposure used to complete the time stack.

This is the foreground exposure used to complete the time stack.

To expose for the clouds I usually use an EV value of -1 or -2. Keep in mind I am using spot metering and I am metering against the clouds and not the foreground.

One of the images in the stack. This image (as well as the rest) are exposed for the clouds.

One of the images in the stack. This image (as well as the rest) are exposed for the clouds.

Step 4. Timing the shot… So this part is kind of tricky. It really depends on mother nature. If the clouds are moving slowly across the sky, then you need to configure your intervalometer to have a longer delay in between shots. If the clouds are going fast, then your delay between shots can be shorter, or you can always leave your delay longer for a “stepped” appearance in your time stack. Taking a couple test shots with a self-timed delay will give you an idea of the movement in the clouds, and how pronounced it is between shots.
For the final image at the beginning of this tutorial, I had a 20 second delay between shots. However, as the sun set, my exposures got longer… to compensate I changed my Fstop for the last 50 images or so to F3.5 (I was at F8 for the first 130 shots).

Step 5. Shoot! Once you know your delay, and once you’ve got your gear all setup, it’s time to just shoot. Set that intervalometer up and let it rip! <NOTE: For a good cloud time stack, I recommend at least 60 images>

Step 6. Post Processing – So we have our shots… lots of them! Now what do we do? Ladies and gentlemen, this is where the magic happens. First let me make a note that there are several ways to do this. Currently I use Advanced Stacker PLUS from Star Circle Acadamy, but you do not necessarily need to pay $42 for this Photoshop Action; I did because it really makes life easy for this, as well as for Startrails… However, the manual method works just as well if your computer can handle loading a lot of files into a stack (consumes mass quantities of memory).

Step 6a (Manual Post Processing). Move all of the images for the stack into a folder that contains ONLY those images (you don’t want your foreground image in that folder, nor do you want any other images in that folder). Go to File –> Scripts –> Load Files into Stack…
TS Step 6
Select the images from the folder you created that only has the time stack shots in it. Click OK for PS to start importing the images…
TS Step 6-2

Select all of the layers EXCEPT the very last layer. Set the blending mode to Lighten.
TS Step 6-3
Once you do that, you should have an image that looks something like this:
TS Step 6-4

Flatten the image to a single layer and that’s it! Ta Da! You now have a daytime time stack… but wait, their’s more! What about the foreground, and the rich bright colors of the finished product? Well, that part is entirely up to your creative process. For me, I wanted an image that showed the foreground and not just a silhouette, but you may want the silhouette, so really it’s just a matter of artistic taste.

I can tell you that I took the image I showed you earlier, added as a layer on top of the finished stack, then masked in just the bits that I wanted masked in. Afterwards I edited the photo further in Nik Color Efex Pro to bring out some of the contrast and color. Don’t worry, if you don’t have Color Efex Pro, you can always boost the contrast and color saturation in Lightroom or Photoshop.

Step 6b (Advanced Stacker Plus Method). To achieve the same results using Star Circle Academy’s PS Action you will have to do the following:
Go to File –> Automate –> Batch…
TS Step 6-5

Make sure your batch settings look something like this (initially):
TS Step 6-6

Click OK once you’ve selected your source folder, and selected the StarCircle action set, with the action of “Do this FIRST.”
The action will open your first and last images, then it will give you a message. Click “Continue” then another message will pop up… On this second message click STOP! Another message will pop up asking if you’re sure you want to stop, click on Stop again.

Now go back to File –> Automate –> Batch, and for the Action select “LIGHTEN Mode – Recommended” Click OK and sit back with a cup of coffee and watch the magic happen… Once the action finishes, you will have to flatten the image and do whatever post processing you want to do in order to achieve the affect your are looking for.

Here are some other time stack images I have done:

LickObservatoryTimestack02 San Jose TS
LickObservatoryTimestack01 SunsetCliffs-TS2

The bottom two images used a slightly different technique. Instead of Lighten mode, I used Darken mode… You may want to experiment with both.

 

I hope this tutorial has been useful to you. If you have any comments or suggestions, feel free to post them.

If you have success with this technique and want to share your results, please do! I would love to see your work.

Good luck and keep on shooting!

 

~Stephen
CreativeMindsPhotographyAndArt

 



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