pindiza
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What is the Rolling Shutter Speed?

Sat Aug 16, 2014 1:14 pm

Does anyone know what the Rolling Shutter Frequency is for the camera module? ... and is it fixed or does it vary depending on exposure parameters?

Say for example I record video using a fixed shutter speed (exposure time) of 1/1000 sec. per frame at 30 fps ... how long does it take the rolling shutter process to complete each scan of all the sensor rows?

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mahjongg
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Re: What is the Rolling Shutter Frequency?

Sat Aug 16, 2014 1:22 pm

you mean speed, not frequency.

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Re: What is the Rolling Shutter Frequency?

Sat Aug 16, 2014 1:34 pm

It varies depending on the sensor mode and exposure time.

Think of the sensor readout as having a "start exposure" line pointer and and "readout" line pointer. The time to read out a line is dictated by the mode but is otherwise fixed. Setting the exposure time controls the number of rows apart that the two pointers are. If you want an exposure that is longer than (line time)x(frame height) then extra dummy lines are added to the end of the frame (and the framerate drops accordingly).
I don't have the line times for each mode to hand, but we do quote the maximum framerate for each mode and that corresponds to reading out the frame with no extra dummy lines on the end. You should be able to work backwards from that to get the line readout time.
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pindiza
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Re: What is the Rolling Shutter Frequency?

Sat Aug 16, 2014 4:55 pm

Great info, thanks!

Just to check ... Is "sensor mode" the same as the modes listed here? : http://picamera.readthedocs.org/en/rele ... mera-modes

Also, one Product Brief for the OV5647 sensor claims it has both Rolling and Global Shutter features. Cameras with this capability are typically much more expensive so is this just a mistake? (http://www.ovt.com/uploads/parts/OV5647.pdf)

Having a Global Shutter option enabled on this camera would be fantastic because I need to measure the relative distance an object moved between subsequent frames, from video recorded at slow FPS but fast shutter speeds. Rolling shutter distortion will obviously play a role, which is why I'm trying to quantify it.

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Re: What is the Rolling Shutter Speed?

Sat Aug 16, 2014 6:53 pm

The sensor we use doesn't have a global shutter. Soz.
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Re: What is the Rolling Shutter Speed?

Sun Aug 17, 2014 10:49 am

jamesh wrote:The sensor we use doesn't have a global shutter. Soz.
Yet that ovt e-flier clearly states
global-shutter1.png
global-shutter1.png (32.83 KiB) Viewed 5530 times
rolling shutter/global shutter!

I've never really believed anything I read on the web.
Last edited by Burngate on Sun Aug 17, 2014 3:56 pm, edited 1 time in total.

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Re: What is the Rolling Shutter Speed?

Sun Aug 17, 2014 12:39 pm

You may look for Point Grey Firefly camera - a lot of them were sold on ebay very cheaply (and maybe they are still there ) - for a webcam price while being USB2 basic mono machine vision camera with a global shutter CMOS. PGR has FlyCap for ARM Linux so it ought to work.

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Re: What is the Rolling Shutter Speed?

Sun Aug 17, 2014 3:08 pm

Burngate wrote:
jamesh wrote:The sensor we use doesn't have a global shutter. Soz.
Yet that ovt e-flier clearly states[attachment=0]global-shutter1.png[/attachment]rolling shutter/global shutter!

I've never really believed anything I read on the web.
I think it might depend on the package the sensor is built in to. Ours doesn't have rolling shutter.
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Re: What is the Rolling Shutter Speed?

Sun Aug 17, 2014 3:59 pm

jamesh wrote:
Burngate wrote:[attachment=0]global-shutter1.png[/attachment].
Sorry for the bellowing - I've toned it down now.I'm not sure how the size tag crept in.

Thanks for the clarification; it makes sense.

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Re: What is the Rolling Shutter Speed?

Sun Aug 17, 2014 4:08 pm

I'm guilty of that, Tried to make the picture bigger, but it doesn't work well with posted attachment pictures as the text below it also blows up. Shan't do it again.... :oops:

Works great with [img] tag pictures though .

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Re: What is the Rolling Shutter Speed?

Sun Aug 17, 2014 4:19 pm

jamesh wrote:
Burngate wrote:
jamesh wrote:The sensor we use doesn't have a global shutter. Soz.
Yet that ovt e-flier clearly states[attachment=0]global-shutter1.png[/attachment]rolling shutter/global shutter!

I've never really believed anything I read on the web.
I think it might depend on the package the sensor is built in to. Ours doesn't have rolling shutter.

In your earlier reply you said it doesn't have global shutter and now it doesn't have rolling shutter so what does it have?

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Re: What is the Rolling Shutter Speed?

Sun Aug 17, 2014 4:22 pm

In your earlier reply you said it doesn't have global shutter and now it doesn't have rolling shutter so what does it have?
I think jamesh made a typo the Pi Camera is 100% rolling shutter from some of the video samples I've seen so far.

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Re: What is the Rolling Shutter Speed?

Mon Aug 18, 2014 7:10 pm

redhawk wrote:
In your earlier reply you said it doesn't have global shutter and now it doesn't have rolling shutter so what does it have?
I think jamesh made a typo the Pi Camera is 100% rolling shutter from some of the video samples I've seen so far.

Richard S.
My understanding is that the OV5647 has both rolling shutter and global shutter capabilities. The rolling shutter is what has been used to date. The global shutter is accessible using the FREX (frame exposure) modes. One of those modes relies on the use of the FREX pin which is not available on the Pi camera connector. Another FREX mode can be triggered through the I2C bus. I expect this second FREX mode could be exploited to provide a global shutter that is usable in the standard hardware configuration.

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