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More fun with long exposure stacking of photos

A few months ago I experimented with Imagemagick by using it to merge very similar photos of flowing water to give the impression of a longer exposure.

Here are a few more examples.

By merging a series of thirty photos taken two seconds apart I created a pleasing image that looks like a sixty second exposure. The day I took these photo was overcast and dull, but not dark enough to do an actual long exposure like that without the help of some fairly dark filters. I used the intervalometer in Magic Lantern to shoot this so I didn’t even need a remote release. My camera did all the work! This was created using the following Imagemagick command line:

convert *.jpg -average average.jpg




I combined 60 long exposure shots of the night sky in the mountains of Utah (during the Automattic Grand Meetup a few weeks ago) to create a single long exposure of the stars moving through the sky. Thanks mkaz for publishing this post on interval shooting where I got this command line:

convert *.jpg -evaluate-sequence max combined.jpg




Finally, another series of sixty shots taken in Utah. The same convert command line was used to process these.




In the image above I should have cloned out the wires in the bottom left of the image. Lightroom makes it easy to make the same modifications to every image. Work on one image, then select all the ones you need and click “Sync Settings”.

It can be frustrating taking these types of photos as your camera is shooting a long series of very ordinary shots, and the final result can’t be seen until the images are processed correctly but it’s certainly worth it.

Update on December 1st: here’s one that didn’t work out so well. It was so windy the camera shook the whole time.

combined photo

Aperture ƒ/4
Camera Canon EOS 6D
Focal length 17mm
ISO 1600
Shutter speed 30s

By Donncha

Donncha Ó Caoimh is a software developer at Automattic and WordPress plugin developer. He posts photos at In Photos and can also be found on Twitter.

One reply on “More fun with long exposure stacking of photos”

Pretty cool —
I’ve long wondered how some of my friends do long exposure photos with hundreds of $Adobe software but being a linux geek,
I’ve always thought there has to be a better way and by better I mean open source 🙂

I’m working off some public domain videos I’m downloading from pixabay –

So I used this video as a basis …

I run them through ffmpeg to extract X number of png files and then these convert commands are working out great –
just has good as loading all of the pictures as layers in gimp and then using GMIC to process.

# ffmpeg -i Milky\ Way\ -\ 10339.mp4 -q:v 1 -r 23 milky_%04d.png
This makes 321 frames
and then
# time convert milky_0* -evaluate-sequence max milky_final2.png

Some of my other water fall conversions (using gimp) but processed with ffmpeg the same way

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