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Guess the Read-out speed


Kitae Lee
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Hello!

In modern digital cinema cameras, the distortion caused by rolling shutters is quite annoying in most cases.

As everyone knows, it is natural that the slower the read-out speed of sensor is, the more severe the distortion is, but the read-out speed of high-end cinema cameras is not very public.

At camera new product presentations and seminars, I asked camera product managers directly about the read-out speed,(Sony,  Black Magic,  Arri) But unfortunately, all the managers of the three companies avoided answering the read-out speed.  I wonder why.

Now, the video below is a somewhat unscientific rolling shutter test video of 8 cinema cameras. It's difficult to judge easily with that video, but what do you think is the reading speed of each camera through your eyes and experience?

My simple unscientific 'guessing' is: (At maximum resolution)
Alexa mini 2.8k = 8ms?
Alexa  LF, mini  LF = 11~12ms?
C700 = 12~14ms?
VARICAM35,LT = 14ms?
RED MONSTRO = 16ms?
VENICE = just  under 10ms at 6k, 5ms at 4k crop

And... I haven't tested Alexa 65 on my own, but when I see several feature films, it feels like 16ms.

Please tell me if you have any experiences.

 

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Hello Kitae, thank you for posting your tests!  It's always good to see what the results look like in the real world - we get a much better sense of each camera's performance by watching the video, versus comparing unofficial estimates.

I also find it frustrating that this information is not published by most manufacturers.  Readout speed is a factual, quantifiable number, just like resolution, bit rate, or power draw.  One would think that manufacturers with low rolling shutter numbers would want to promote it. 

There's a long-running thread on DVXuser.com with a list of rolling shutter figures: http://www.dvxuser.com/V6/showthread.php?303559-Measuring-rolling-shutter-put-a-number-on-this-issue! Though those figures might not be entirely accurate, the people involved seem to have done their best to get as close as they can.  

Cinema5D.com has recently changed their method for measuring rolling shutter, filming a 300Hz strobe and counting the number of pulse lines per frame.  This seems like a repeatable method that will be much more accurate than guessing based on panning a camera back and forth.  Unfortunately, they've tested very few cameras with their new method.  

It could be possible to construct a portable 300Hz strobe tester - something like an Expodisc diffuser with an LED strobe behind it, that could cover the front of a lens and be taken to a trade show (whenever we have public trade shows again!), rental house, or retail showroom.  If we have to measure these numbers ourselves, it would be best if we could eliminate the guess work. 

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22 minutes ago, Daniel Klockenkemper said:

Cinema5D.com has recently changed their method for measuring rolling shutter, filming a 300Hz strobe and counting the number of pulse lines per frame.  This seems like a repeatable method that will be much more accurate than guessing based on panning a camera back and forth.  Unfortunately, they've tested very few cameras with their new method.  

It could be possible to construct a portable 300Hz strobe tester - something like an Expodisc diffuser with an LED strobe behind it, that could cover the front of a lens and be taken to a trade show (whenever we have public trade shows again!), rental house, or retail showroom.  If we have to measure these numbers ourselves, it would be best if we could eliminate the guess work. 

Hello Daniel!
Thank you for your kind reply.
I fully agree with your comments.
That video was shot in 2019. The place is a show called KOBA. It would be nice to understand that this is a tiny version of the NAB show in South Korea. And I was planning on retesting with a 300hz LP player test strobe and diffuser at KOBA in May this year(as you mentioned), but the KOBA show was unfortunately canceled because of the coronavirus (like the NAB). I think I should probably wait until next year!

Edited by Kitae Lee
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