I’ve seen the term used for night photography.
What exactly is happening?
In: Technology
It’s taking a series of images you’ve captured and merging them into a single photo via software. This is done because every picture used will bring up more detail in the final ‘stacked’ image.
It’s to make a perfect picture. At this point, it’s not so much photography, as it is using a camera and computer to make art.
Why do people do it? Like I said, to make a perfect picture. Maybe it’s combining things that aren’t really at the same location, or maybe it’s because you can’t take a photo like that.
For example, we’ll use [this picture.](https://www.instagram.com/p/CCgwvgAArjp/?igshid=e153rcx9pseb) since the photographer told me how he did it.
He used three photos to make it. One was with the proper settings to capture the milky way. Two was proper settings to capture the building. Three was to capture the foreground. To capture the milky way, he would use a relatively short shutter speed to avoid having the stars leave trails. To capture the house he would use a longer shutter speed to capture the lights (which aren’t as bright as they appear. That’s a benefit of a long exposure, duller lights will appear brighter.) And then another shot but with lights on the foreground. All shot with the camera at the same place. As you can imagine, you can’t have a shutter speed of 30 seconds, and 15 seconds at the same time. There’s also other camera settings such as aperture that would be changed.
Another example would be taking a picture of the milky way, and then putting it in the background of a local landmark where there’s too many city lights to see the milky way.
Image stacking is the process of taking multiple photos of the same object at the exact same settings and taking a pixel by pixel average.
It is not a process of taking multiple pictures with different settings and combining them artistically as another poster said. That is called High Dynamic Range (HDR) processing.
Image stacking is done because objects in space are really really dim. To get something to show up you have to leave the shutter open a really long time (hours, not seconds). But since the sky moves, tracking the sky accurately is essential. Tracking errors will make stars look like ovals (or worse, streaks).
So instead of trying to take 1 four hour (240 minute) photo and hope tracking errors don’t destroy it, you take 150 two minute pictures and figure on throwing 30 of them in the trash. This would leave you with the same 4 hours worth of “data”.
Once you align (register) the images, software calculates an average value for each pixel. The noise (random error) averages away leaving more of the true image being noticeable. But because it’s a two minute exposure instead of a 4 hour exposure, it’s still pretty dark. Further processing is needed to increase brightness, contrast, sharpness etc, same as any other photo. If you did this without stacking, you would be brightening all the noise too.
Latest Answers