How does a long exposure still differ from stacking frames from a video?
Asked 6/22/2013
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If a camera sensor receives light for the same total amount of time, what is the practical difference between one long-exposure still photo and a video recording made over that same duration? Can you create a similar night long-exposure effect by stacking the video frames afterward?
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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The biggest difference is that a single, long exposure, photo is a single read off the sensor and the video stacking isn't, it's a sequence of frames, probably taken 25 or 30 times in a second.
In terms of single versus stack, well, I can think of a few things to bear in mind with video:
- Video frames are usually smaller in size (length/width) so level of detail for same field of view will be sadly lacking.
- You may need hundreds, or more, video frames to get the same exposure time.
- You may need to boost the ISO to get a reasonable amount of data in the short sequence of time between reads on the sensor.
All in all, I'd suggest you'll get much better results with a single shot. Stacking, by the way, is common in astrophotography, though, as @jrista notes in the comments, you can't get the long exposure effects of light blur with the source removed as a result of speed of movement.
Originally by user472. Source · Licensed CC BY-SA 4.0
user472
13y ago
0
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A long-exposure photo and a video of the same total duration are not equivalent in practice.
A long exposure is one continuous capture with a single sensor readout. Video is many short exposures, each read from the sensor separately. That repeated readout adds limitations and usually more noise than one single long still exposure.
Other practical differences:
- Video frames are usually much lower resolution than still photos.
- To equal a long exposure, you may need hundreds of frames.
- Each video frame is exposed for only a short time, so the camera may need higher ISO/gain, which reduces image quality.
So yes, you can theoretically stack video frames to simulate a longer exposure, and stacking is a real technique used in areas like astrophotography. But it usually won’t match the quality of a true long-exposure still, especially with a webcam or typical video mode.
In short: same total light time does not mean same result, because capture method, readout, resolution, and noise are different.
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