What Exactly Is Image Stacking?

If you have ever seen images of deep space objects like nebulae and galaxies while perusing the internet today, you may have wondered why they look the way they do. I mean, it’s not all difficult to point your camera up and take pictures of the night sky. But there’s a lot more to it than that.

Anyone can take pictures of stars or even the Milky Way. But most people just getting into the hobby tend to rely on their camera's noise performance to take one photo of the stars with perhaps an interesting foreground. But have you ever considered taking more?

In this video by astrophotographer Nico Carver, who goes by Nebula Photos on YouTube, the term “Image Stacking” is completely demystified by him showing the process of taking multiple sub-exposures and combining them into one photo. Nico very carefully explains the math behind why taking many sub-exposures and stacking them is preferable to taking just one long exposure. We get to see the process and comparisons along the way, from one to four images, through 16 and 64, and finally to 256 and 1024 images, respectively. He shows cropped comparisons between the different image sets to reveal the process even further, highlighting an increase in detail, and a decrease in noise with each consecutive set. 

I have been enthusiastically taking astrophotos for years now, but I never actually went through this process myself or took the time to completely understand the math behind it. I was seriously amazed, though, at the fact that he accomplished this task without a star tracker. Now, to be fair, he did use a Canon EOS Ra, which is an off-the-shelf astro-modified camera. But the only advantage that specific camera gave him was the ability to use far fewer photos, as the Ra is more sensitive to near-infrared light. That aside, anyone can use this video to further their understanding of the image-stacking process.

Scott Donschikowski's picture

Scott Donschikowski is a professional photographer and educator with over 11 years of experience leading a variety of photo workshops around the world. He specializes mainly in landscape, wildlife, and astrophotography. He is also active on YouTube where he makes tutorials sharing his photographic knowledge.

Log in or register to post comments