On Monday evening, I took 42 lightning photos without moving the tripod. When all 42 exposures are stacked together using a brightest pixel to the top of the stack algorithm, the above image is produced. As you can see, lightning filled the sky over Washington during my photo shoot which began at 9:15 p.m and ended at 9:55 p.m.
Stacking lightning photos is a popular technique for weather photographers. Lightning stacks can be easily created with Adobe Photoshop and other imaging software, provided that the camera’s settings and the tripod position remain fixed during the photo shoot.
Each individual lightning photo becomes a layer within a stack of lightning images and the brightest pixels from each layer are moved to the top of the stack. This process forms a composite image that displays all of the lightning bolts and the brightest areas of the sky together into a single view. The resulting image is always brighter and more vibrant than any of the contributing photos.
One of the side effects of stacking lightning photos, however, is that some of the brighter bolts tend to wash out some of the less bright bolts. Thus, the composite image will lose the delicate branching of lightning that is visible in a single exposure. Only the biggest and brightest bolts will make it into the final composite stacked image.
Below is a lightning stack produced from a photo shoot at the same location about four years ago. The composite image shows the nature of the thunderstorm was different than the storm Monday evening. Most of the visible lightning bolts were cloud-to-ground. There were not many visible anvil crawlers on that stormy night in July.