Long exposure time lapse

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chrisconway

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  • Joined: Mon Aug 31, 2015 11:48 am

Long exposure time lapse

PostSun Aug 13, 2017 7:01 am

Is it at all possible by BMD to allow the shutter to open for longer when set up for time lapse. E.g 180 degree or 1/2 second on a 1 second interval time lapse. I have a Ursa Mini 4k, but think this applies to all. It's just a lens and sensor with a gate between. Is there a technical barrier here that I am missing, or has it just not been considered to implement. I can only imagine what great time lapse could be created.
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Anatoly Mashanov

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Re: Long exposure time lapse

PostSun Aug 13, 2017 8:22 am

I've tried to somehow sum the BMPCC footage in order to make it appear as a single 1-2 seconds exposure. Results are quite discouraging: the vertical stripes that are almost invisible in separate frames become clearly visible.
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chrisconway

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Re: Long exposure time lapse

PostSun Aug 13, 2017 9:57 am

Hi Anatoly,

Thanks for replying but I am not looking to fudge anything, I am just enquiring if the Blackmagic cameras can open their shutters for longer periods when the time lapse feature is engaged. Is it a mechanical issue or software issue.

Chris
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Robert Niessner

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Re: Long exposure time lapse

PostSun Aug 13, 2017 6:56 pm

Chris, I too have requested this feature then for the BMCC - years ago.

But I think there is a good reason why this won't be implemented with the current hardware and firmware. With longer exposures beyond 360° you quickly start to get into all kinds of sensor noise issues where the implemented calibration won't work as expected anymore. And stuck or hot pixels and so on.
Like Anatoly wrote with averaging frames and getting vertical stripes this would also show up with those much longer exposure modes. Blackmagic would need a different approach for sensor calibration and in-camera noise reduction which is likely not happening anytime soon or maybe even impossible.

So your best bet would do what Anatoly did. Average out and fuse several frames into one. And you would need somehow to create a reference frame for subtraction to cancel the vertical stripes out in post.

https://wiki.apertus.org/index.php/Black_Calibration
https://wiki.apertus.org/index.php/Pattern_Noise
Robert Niessner
LAUFBILDkommission
Graz / Austria
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chrisconway

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Re: Long exposure time lapse

PostSun Aug 13, 2017 8:38 pm

Hi Robert

Thanks for clearing that up. I will stick to my mirror less camera for those types of shots then.

Cheers
Chris

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