Night Photography Explored: Part 6 – Post-Processing

Northern Lights and Star Trails

Post-processing can be a very tricky, and often subjective, part of the photo creating process. It opens the door to a number of different formulas, styles, and personal tastes. As a result, I’m only going to explain what I would do in the situations I’ll discuss, primarily using Adobe Lightroom. I take advantage of Adobe Photoshop for some more unusual edits, which we’ll discuss. Regardless, this doesn’t make my edits right or wrong, and they’re certainly not a definitive guide on how to process an image, but it’s how I like my night sky images to look, and therefore, it’s what I know. There are a number of other techniques and styles to look into as well though, so the important factor is finding a style that you like and enjoy and incorporating your own personal tastes into that.

Post-Processing Dark Sky Photography

Quite often, your Milky Way images and dark sky photography will come out darker than what we normally think of as acceptable for a standard landscape or portrait image. This can not only be normal, but preferable. The reason lies in the histogram. In looking at a dark sky photograph, you’ll notice the information is heavily favored to the left. These aren’t shadows that are detracting from the image, this is the actual night sky acting as the backdrop for the stars and therefore, the bulk of your photo. You may even have a ground-based silhouette in your foreground, which will also be dark, adding to the shadows. Trying to offset these shadows and lighten them up will only wind up detracting heavily from the drama and wonder of the night sky. Therefore, with most night sky images, you’ll want a histogram that actually favors the left rather than the right.

Milky Way Over Teton Mountains
histogram

Maintaining the stars and Milky Way (if it’s in there) can be delicate process. On one hand, you don’t want a bunch of overexposed objects, and on the other, you want to preserve the darkness that brought you all the way out to that location in the first place. With white balance, I’ve often begun with the Fluorescent setting and then made a few tweaks from there, often bringing back the temperature and tint slightly closer to blue and green, respectively. This of course depends on your camera’s configuration and how it handles color, so not all settings will be the same across the board. Put simply, you want your stars and Milky Way as close to white as possible. For exposure, in most cases, you won’t want to push it up very much at all. This will reduce the overall contrast and begin washing out the darkness of the sky. Likewise, I tend to prefer pushing up the contrast in dark sky images. The helps to set apart the darkness of the night sky with the stars, creating more depth in the sky.

edits-basic

Going down the list of the editing tools in Lightroom, I actually begin with the whites. I’ll push that up until the brightest parts of the histogram begin to create a very small spike, and in some cases, won’t even go that far. You essentially just want to make sure those stars are as bright as possible without completely blowing them all out. I next move down to the blacks and adjust that to really define a particular silhouette or the darkness of the sky. From there, I adjust the highlights and shadows accordingly to better define those areas. You’ll notice highlights have an important role to play in the definition of the Milky Way, and unfortunately, light pollution as well. Depending on the amount of light pollution in your image, you may even want to turn that down to drown out (so to speak) the effects of it. Under Presence, I actually find turning up the clarity some helps to define the edges around the night sky and the stars, and especially the Milky Way. Vibrance and saturation can also be applied as you see fit.

Moving down the list of edits, the curve can be applied as much or as little as you want. This goes back to personal taste. Too much though and you raise the potential for creating shadows that are too harsh, and the same with the highlights. Below that, I often don’t alter the specifics of the color very much. I find the night sky already beautiful as is and don’t believe that it needs my improvement. Again, this is simply personal taste though. Feel free to experiment and see what kinds of effects you like.

Detail is an important feature since that has Lightroom’s built-in noise reduction. You want to apply this enough so that it noticeably reduces the noise present, but not so much that it smooths out the details in some of the finer details. It’s a balancing act that all depends on the initial ISO and how well your camera handles it. A similar mindset applies to sharpening since that depends on both the sensor and the intended usage. You’ll notice that increasing the sharpness also defines the noise, so be careful with how much you apply. Below that lens correction should always be applied. Depending on the lens and how much vignetting it produces, you may need to go back and redefine a few edits.

Post-Processing Moonlit Photos

As you’ve probably already noticed, moonlit images appear much more like normal landscape photos. In this sense, post-processing is also very similar. For this reason, you may even already have a workflow that you prefer and enjoy which could be easily applied to such images.

With most moonlit images, I’ve found the Daylight setting to work best for white balance, barring a bit of tweaking to ensure whites are truly white. Beyond that, many of the same rules apply: center-weighted histogram; whites and blacks toward the edge of the histogram; appropriate contrast; etc. You can essentially treat your moonlit landscape photos the same way you would if they were lit by the sun. In these types of images, you frequently have more flexibility with curves as well.

Post-Processing Northern Lights Photos

histogram and auroras

Processing photos of the auroras can be treated much like dark sky photos, however, there will be a large band (or bands) of bright color stretching across the sky. This adds an extra variable, but for the most part, the same rules apply as if we were processing a standard dark sky image. In essence, following those rules will even get you to a good starting off point.

As with dark sky photos, you want to pull the whites up until they begin spiking in the histogram. In doing so, you’ll notice a more direct effect on the auroras themselves. It’s important not to get them to blown out as well, something that can also be adjusted using the highlights slider. The key difference between processing photos of the northern lights and standard dark sky images is that you want the auroras to appear like they’re bright and glowing, but not completely washed out. Therefore, you can make many similar edits as you would with a dark sky image void of auroras, but be sure to keep an eye both on the intensity of the northern lights and the histogram to make sure all your values are still manageable. You’ll see the colors in the histogram more toward the right side with much of the other information toward the left.

Creating Star Trails

startrails

Remember all those dozens, and maybe even hundreds, of shots you took of the night sky? This is where we start putting them together to get something interesting. Keep in mind, there are dozens of methods to creating star trails. You can do a search for a tutorial and find a plethora of different ideas and techniques. I’ll be sharing with you one of my preferred workflows that offers a few extra bonuses.

Head over to this page to download the Creative Star Trail script. You can download it to wherever you want, and once downloaded, will allow you to take a large series of images, and automatically stack them together with a creative effect built-in. This same process can be done manually, but with plenty of images, it becomes extremely tedious and time-consuming.

Once installed, open Adobe Photoshop and go to Files -> Automate -> Load Files into Stack… Select all the images you want to use and allow Photoshop to work. While that’s working, you’ll want to make an easy edit to the script to tell it what kind of processing you want it to do. Don’t worry, it’s not in use while Photoshop is acquiring the images so it’s perfectly safe to modify the file at this time. More detailed instructions can be found on the Creative Star Trail script page, but the settings I tend to frequent most are leaving the Blend Mode at Lighten, and using either 0 (standard star trails) or 3 (faded star trails) for the style.

Once Photoshop has all your images stacked, go to File -> Scripts -> Browse… and navigate to where you downloaded (and edited) the script. Select it and it will begin working on its own. Once it’s finished, you’ll have your star trail image! From this point you make edits just as you would with any normal photo. I personally prefer to save it and then import it into Lightroom, but that’s just personal preference.

Creating a Time-Lapse

While waiting for all those images to stack, you can actually take the same images and make a time-lapse video out of them. Bear in mind doing so will put a bit of a strain on your processor, but if it can handle it, you might as well. In creating a time-lapse video, I first apply all the standard edits to my files and then export them as high-quality JPEGs. TIFF files could be used as well, but for general purposes, a high-quality JPEG will retain all of what we need, and also because most video editing packages don’t (yet) read RAW files.

Once you have all the exported files in one place, you can open virtually any video editing software and once you select the first image, many will automatically know to look for a sequence of other images. This may be an option that needs to be checked depending on the software, but it should be a straight-forward process. Upon doing so, the software will have all the images imported as one “clip” that can be dragged onto the timeline. (If you’re not familiar with typical video editing software workflow, you may want to do a quick search for a tutorial on the subject.) Once there, it can be exported as a clip.

If you’d like a more detailed walk-through, I have a blog post on how to make a time-lapse video here. This will take you through step-by-step of the entire process.

You should have everything you need from this point forward to begin creating some amazing night sky photos! Don’t let clouds discourage you either. Sometimes a partly cloudy sky can deliver some very dramatic results.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.