This is the second in a series of articles written to help our Irix shooters and others understand the process of capturing the Milky Way. Part one of this series focused on preparing for and completing the shoot. This post will discuss processing single exposure photos of the galaxy.
Before we start…
We’re going to take a moment here to mention our flagship lens. It’s become one of the most popular lenses available among astrophotographers around the globe.
We’re talking about our 15mm f/2.4 lens, of course. With its wide field of view, near-zero barrel distortion and aberration-free imaging, it’s outshining all the competition. It’s also affordable! Click the image below to see for yourself!
What’s the right way?
It’s important to understand that there isn’t a “right” or “wrong” way to process Milky Way images. There are several applications that can be used, and there are many options that can affect the final image. On the other hand, there are key aspects to producing a pleasing image, such as sharpness.
One of the most important factors that will affect your images is your personal opinion. For instance, some photographers prefer to adjust the image to show more blue in the Milky Way, while others process for more yellows or reds. You can opt to try to remove colors caused by light pollution or leave them as-is for a more “natural” appearance. The results of your efforts will depend on what you are looking for in the final image.
Editing Software for Milky Way Photos
As mentioned above, there are several applications that may be used to edit your images. Many are cross-platform applications, while others are developed specifically for one operating system. Unfortunately, menus and procedures vary widely between those applications.
Given the differences and the fact that this article isn’t written to endorse any particular applications, we won’t be providing detailed instructions. We will, instead, be providing a general overview of the steps that may be taken. Please refer to the documentation for the software you use for specific instructions.
Our only specific recommendation for an application would be the ability to work with RAW files. If you’ve read Part 1 of this series, you’ll know that by saving your images as RAW files during the shoot, you’ll have much more opportunity for adjustment.
White Balance Adjustment
Although your own workflow will determine which adjustments should be made first, we’ll begin with one that was mentioned in referring to personal preferences. White balance adjustment will affect the overall colors in your images. If you want to shift the colors in the Milky Way, you can use this adjustment.
A good method to “center” your white balance before you adjust it to your taste is to first increase your vibrance and saturation settings to 100%. Then adjust the white balance to produce a relatively even amount of yellows and blues in the (now splotchy) image. You can then reduce the vibrance and saturation to zero and you’ll have a fairly even place to start.
A setting somewhere between 3700K and 4200K will usually give you the best results. The darkness of your shooting location will make a considerable difference and any light pollution reflected on clouds will also need to be considered.
Find the white balance setting that appeals to you the most and be sure to keep an eye on its effect on any foreground colors. You may have to apply some masking to get the colors you want. When in doubt, choose the setting that makes whites as white as possible.
When shooting the Milky Way, you will normally be using a fairly high ISO setting and your exposure times will be longer than usual. Both of these factors increase noise in your images. At some point, you’ll need to reduce that noise. It’s best to magnify the image to 100% for this step.
If you’re creating a web-only version of the photo, you may be able to use very slight noise reduction. For medium to large-scale prints, chances are you’ll need to be a bit more aggressive with your settings. Keep in mind that noise reduction tends to soften the overall image.
Masking Milky Way Images
There are several reasons to learn masking techniques with single exposure images of the night sky. One of the most obvious is that it’s very difficult to expose for the sky and the foreground simultaneously. If you’re working without supplemental lighting, it’s next to impossible.
In cases where you’re simply trying to balance the exposure between the sky and ground, a select tool may give you an accurate enough mask, especially if you feather the edge slightly at the horizon. You can then use exposure adjustments on the portion you want to correct.
Other, more complex masking methods may help emphasize portions of the sky and/or foreground. Luminosity masking is a good example, and even simple, single-level luminosity masks can be very effective.
Masking is an extensive subject, so we won’t cover it in depth here. Instead, we’ll simply provide links to two video tutorials we believe are worth taking the time to watch:
How to use layer masks in Photoshop by Phlearn
How to create luminosity masks in Photoshop by Greg Benz
Please note that these are not complete masking courses, but then will provide you with a good start and give you an idea of where to learn more.
Once you’ve established a mask to separate the foreground and sky, you can make adjustments to the individual areas. Generally, those adjustments will involve contrast, saturation and/or vibrance and sharpness.
When working on the foreground, look for good detail and shadow definition. You may also find that the ground has a slight color cast, which can often be eliminated by simply decreasing the overall saturation in the foreground.
Contrast adjustments come in several “flavors”. See what your editing software has to offer and use the ones that work best for you. You may want to do some extra noise reduction in the foreground, since noise will tend to concentrate more in shadow areas.
Sharpening should always be your last step. Whatever methods you use, keep your adjustments gradual and check the image at 100% often, to make sure you don’t reintroduce noise.
Adjustments to the sky are basically the same, but remember that this is the part of your image you want to really stand out. It’s worth taking some extra time here to really make the Milky Way “pop”.
Adjustments to vibrance and saturation will help bring out the colors you want to highlight in the galaxy. Contrast adjustments, particularly curves, will help the stars and nebulous areas stand out.
Luminosity masking can help adjust areas of the sky you’d like to brighten or dim as well as adjustments to color, etc.
Once again, save the sharpening for last and go easy. Check at 100% magnification and watch for jagged edges around bright spots.
Create your own workflow
Once you’ve learned the basics of processing Milky way photos, it pays to pay attention to the steps you take and the adjustments that work best for you. Continuing to do this will help you develop a workflow that helps you complete your edits in less time and increases your confidence in the outcome.
Part of that workflow should be saving your images in the sizes and resolutions that you’ll use for web images and for prints. This saves work in the future.
We’re not quite done with this series! Or next tutorial will discuss another method we touched on in Part 1: stacking.
Noise reduction and sharpness can both be improved by stacking and blending multiple images when creating Milky Way images. You can also focus stack foreground images to improve front-to-back sharpness.
We’ll provide the details in Part 3. Meanwhile, don’t forget to share your Milky Way photos with us. Tag @irixusa on Instagram or Twitter, or send them to us using messenger on Facebook: https://www.facebook.com/irixusa/