Measuring rolling shutter: put a number on this issue!

[Samuel H]

^ that

I wouldn't have posted that "9.3" number, since we're not sure yet about what the optimal settings are for the GH3
but now that it's online... this is the chart with those settings (in thirds of a stop):

[FrameFarmMedia]

thanks. I would have guessed 1-2 stops more than GH2 by eyeball but have never measured (I'm not that technical minded).

I have found that the GH3 has much more recoverable shadows than the GH2.

[Wesley Byram]

Ok, so there is obviously no way to test this yet, unless John Brawley or another BMD rep decides to submit a sample, but because I'm bored at the moment, I'm going to make a prediction on the performance of the BMC-Pocket. JB has stated a couple of times that the chip in the Pocket is an S16, 1080p version of the ~2.5k chip in the BMC mk1. Knowing that the number of active photosites on the Pocket sensor is about 64% of that of its big brother, and assuming all other things being equal, we would expect a readout time of about 64% of the BMC sensor as well. That would put the Pocket at 15.6 ms, within the ballpark of the GH3 and dedicated video cameras. Not bad at all, really.

Of course, this in only informed speculation. It may not be that simple, and I could be totally wrong. The one sample video we've seen had a decent amount of movement, and no perceptible jello, so I bet it's not that far off. I'm curious to see how close to the truth that 15.6 ms number will be.


Update: Looks like I was off. My estimate falls short by 2.2ms.

[North Utsira]

I joined dvxuser pretty much so that I could say THANK YOU for putting this thread together. Jello has been so much a part of the DSLR video experience, it's incredible in a way that no-one thought to comprehensively measure it before now. I love how people are reverse engineering the cameras to reveal the really important stuff the manufacturers won't tell us. These results show you can't necessarily make assumptions based on sensor size, or the previous implementations of a given manufacturer.

I see a lot of jello in some of my NEX-5N footage. I always thought it was a combination of my crappy technique, use of non-stabilized vintage lenses, refusal to use any kind of stabilization, and copious coffee intake. Now I know it's actually the camera's fault

Seriously though, I'm thinking of getting a D5200, just to have something that's slightly better balanced with Nikkor lenses than using 5N+adaptor. And according to the results here, the D5200 has around a third less rolling shutter than the 5N. I tried putting my lenses on a friend's D5100, and I liked the ergonomics a lot better.

Interesting that jello on the 5N is less at 60fps than at 24fps. Anyone have any guesses as to whether any other settings on the camera could affect the amount of rolling shutter?

[Samuel H]

You're welcome

AFAIK, the only settings that will affect rolling shutter are things like fps and cropped view and such. Basically, read-out speed is a very deep characteristic of the sensor, there's not much you can do to make it faster, except read it in a completely different way.

[john flores]

Good work, gentsM

[Samuel H]

I just added the results for the BlackMagic Pocket Cinema Camera: very impressive, at 17.8ms

Even so, there are lots of complaints around about the awful rolling shutter in that camera. My guess is that this is caused by the size and weight: it is so tiny that it will move around a lot more unless you add weight or treat it very gently.

[Samuel H]

Just added: Sony RX10.
It's the fastest rolling shutter I've measured so far, at 14.8 ms, right in expensive-camera territory. Thanks to Wesley Byram for sending me the clip to measure this.

[aldolega]

Someone please measure the GH4 in 1080, VFR, and 4K modes!

[Samuel H]

I'd definitely be interested in those numbers. The GH4 and the a7s are the hottest cameras right now, and only one of them is in the hands of users. Haven't had luck asking for this in the GH4 subforum, though.

[c3hammer]

Are you guys getting radically different numbers between 24p and 60p on a cam? My G6 is giving 15.15 in 24p but only 5-6 in 60p. I've been through the calculations a dozen times and 60p is always a much lower number. Surely sensor read out has nothing to do with frame rate?

[Samuel H]

The measurements I took are all at 24p. In some cameras (for example my NEX-5N), it does change with frame rate, because a lower portion of the sensor is read at higher fps, and this makes read-out times faster.

[storyteller]

Great work guys! Probably would help to have several independent tests of each camera. Also, any way to have one, consolidated, running list?

[Samuel H]

I'm not sure we would gain anything by having more than one person testing each camera: I designed the test to average out all inconsistencies and give out an objective, quantitative measure. But if you are not convinced and you have any of the cameras we have already tested, you can send me a new file and we can see if it actually changes or if it doesn't (my guess: it will fall within 2ms of the number we already have).

[blazer003]

Hey, so I made some clips for you this morning with the GH4. Did it in all pertinent modes and framerates (doh, I forgot to do variable frame rate 96fps, I'll try to upload that later).
http://www.ecf.org/wp-content/upload...s/103_PANA.zip
C4K 24p
UHD 24p, 23.97, 29.97
1080p 24p, 23.93, 29.97, 59.94

*Edit* So I should have read your directions more carfully. Is there a reason to do a 180 degree (1/50 sec) shutter? It seems that sensor readout speed shouldn't be affected by this, and less motion blur, the more accurate, right? I can reshoot again if need be.

Assuming shutter speed isn't an issue, I ran the numbers on a couple frames.
Cinema 4K 4096x2160 @ 24p I came out with .0203 seconds or 20.3 milliseconds.
1080p @ 24p I came out with .0133 seconds or about 13.3 milliseconds.

We'll see how Samuel's numbers come out.