A stacked image shows 42 lightning photos combined into a single image with the brightest pixels from each photo moved to the top of the stack.  The resulting image shows all of the of the lightning bolts together.  The photos were taken Monday evening between 9:15 pm and 9:55 pm. (Kevin Ambrose)

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.

This is a single exposure that became one layer in the lightning stack. This was a six second exposure with ISO 50 and F/5.6.  Some of the less bright portions of the lightning in this photo washed out in the composite stacked image. (Kevin Ambrose)

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.


Photos: Lightning crawlers crisscross Washington, D.C. skyline

Stacking lightning bolts over Washington, D.C.

A stacked image shows 34 lightning photos stacked into a single image with the brightest pixels from each photo moved to the top of the stack. The photos in this composite image were taken July 11, 2011. (Kevin Ambrose)