Can I simulate a 2-minute long exposure by stacking shorter exposures in Photoshop?
Asked 9/25/2012
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I shoot daytime long exposures to blur moving clouds, aiming for around 2 minutes. With a 9-stop ND filter plus a CPL, I still can’t always reach that shutter time. Can I get a similar result by taking several shorter exposures—such as six 20-second shots on a tripod—and blending or stacking them in Photoshop? If so, what blending method should I use to mimic the look of one long exposure?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
13y ago
2 Answers
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Yes, you can. I have never tired it for clouds but I have for water falls. My usually way of operating is to use my in camera multiple exposure but doing it in Photoshop works too.
For in camera set your camera to do n multiple exposures and allow it to figure out the auto gain. Shoot n pictures. Done
For in Photoshop take your n pictures as normal. Then bring them all into Photoshop as layers in a single image. Execute the command Edit | Auto Align Layers. This will line up your images to compensate for any variation. Then blend each layer using Normal mode but a lower opacity. This is where some experimenting will need to be done but you can find a opacity that makes things look good. Usually you want that to be the same for all the layers. Start with setting all the upper layers to 100 / n percent opacity and go from there.
Originally by user20973. Source · Licensed CC BY-SA 4.0
user20973
13y ago
0
Generated from our catalog & community — verify before relying on it.
Yes—stacking multiple shorter exposures can approximate a single longer exposure, especially for motion like clouds, water, or star trails.
A practical method is:
- Shoot a series of frames from a tripod, ideally with minimal delay between shots.
- Load all images into one Photoshop document as separate layers.
- Use Auto-Align Layers if needed to correct tiny shifts.
- Blend the layers by averaging them: set equal opacity for each layer, or use a workflow/action that averages the frames.
This works because averaging multiple exposures can produce a similar cumulative blur to one long exposure. Keeping the interval between shots short is important; large gaps can make motion look less continuous.
Some cameras also offer an in-camera multiple exposure mode with auto gain, which can achieve a similar effect.
It may not be perfectly identical to a single uninterrupted 2-minute exposure in every situation, but it is a valid and commonly used technique.
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