Measuring rolling shutter: put a number on this issue!

With an additional 1.7x crop over APS-C, if it's the same sensor and it works at the same MHz, it should be somewhere around 20ms, which would be the fastest RS in 4K mode on a cheap camera. The test looks good, I'll see if I can pull the numbers out of it, in a day or two...
 
^ That came out just under 32ms, which means RS is not improved (previous measurements 30.6-31.6-31.4-30.7-30.2).

The new 1080p mode (with more of the sensor being read) may be slower, but apart from that I really don't expect a firmware update to change rolling shutter.
 
So the NX1 @1080 is king, but it you shoot it at UHD and downrez to 1080 (for that quality bump) it is not, am I reading this right?
 
Exactly. Use UHD in general (adjusting framing in post is really useful), switch to 1080p for shots where RS may be an issue.
 
I added the numbers for the a7R II, using this test

a7R II 4K FF ---- 19.9 ms (19.3-19.6-19.4-21.2)
a7R II 4K S35 --- 34.0 ms (35.6-32.2-32.8-35.3)

there's some discussion about it here
 
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Samuel H said:
I still have no proper test for the NX1, a7II, or 7DII. I'd love to get them, particularly for the NX1. I have no interest on the 7DII, and same for the a7II unless the IBIS is useful for video (which seemed not to be the case with the original firmware, but may be with the recent update).
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You may like the 7DII for face tracking for interviews. It is VERY GOOD. I bought two + Sigma 18-35 for this very reason. No more focus hunting for head shots!
 
Not even close to Dual Pixel AF. In fact, pretty unusable for professional environments on the NX1.

Thanks for the RS tests Samuel. The A7rII 34ms is shocking. The D90 was in the unusable territory for me, you really couldn't move the camera at all.
 
Shouldn't the film RS be the same as the shutter duration? This would be 1/48 second at 180 degree shutter which works out to 0.02083333 seconds???

I know it is old and unwanted, but would numbers from a gh2 be of any value?
 
No, it's the time the edge of the disc takes to go from the top of the frame to the bottom of the frame, and it depends on the size of the rotating disc. With a disc that is three feet wide it would be basically zero but the camera would be unwieldly; the smaller the disc, the longer this takes. The disc would be always rotating at the same angular speed, but linear speed at the point it crosses the frame varies with the diameter. No idea which camera that measurement refers to.
 
So for film it is the time it takes for the leading edge of the disk to travel from top of frame to bottom of frame, plus the time for trailing edge to travel from top of frame to bottom of frame? I guess that makes sense because everything that happens during full open shutter is just blur. Or is it only the trailing edge that really defines the RS properties? Anyway, now I have a better understanding of why a film camera is different.

Makes me think we are nearing a time where putting mechanical round shutters back on digital cameras might be useful. Any imager that can read out 48fps should be able to handle a 180 degree disk shutter and only read out during the dark cycle (at 24fps), this should offer a similar RS value to film. Bosch (BTS) did something similar in their TV cameras years ago to produce FT (frame transfer) CCD based images.
 
Another user has posted this video with an attempt to minimize the problem:


How would you measure it after post?
 
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Greg_E said:
So for film it is the time it takes for the leading edge of the disk to travel from top of frame to bottom of frame, plus the time for trailing edge to travel from top of frame to bottom of frame? I guess that makes sense because everything that happens during full open shutter is just blur. Or is it only the trailing edge that really defines the RS properties? Anyway, now I have a better understanding of why a film camera is different.

Makes me think we are nearing a time where putting mechanical round shutters back on digital cameras might be useful. Any imager that can read out 48fps should be able to handle a 180 degree disk shutter and only read out during the dark cycle (at 24fps), this should offer a similar RS value to film. Bosch (BTS) did something similar in their TV cameras years ago to produce FT (frame transfer) CCD based images.
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Yes it's completely possible technically to use a real, mechanical rotary film shutter on digital cameras to get the same rolling shutter performance of film (almost none) but not economically possible. To get an idea, take a look at the digital cameras that do use this, most recent and current example is the Sony F65. It uses state-of-the-art most technologically recent mechanical shutter, yet it's still a gigantic beast, produces sound, and costs in the thousands of dollars. So it's not anytime soon we'll be using mechanical shutters on our digital video cameras since the development has stopped on that concept and is now completely focused on the other ways of eliminating rolling shutter (Faster rolling shutter sensor readouts and Global shutter sensor technology). In the future, when Global Shutter sensor technology is mature enough, it will potentially replace all types of shutters including mechanical stills shutters on photographic cameras and of course eliminate rolling shutter artefacts entirely. It's the best option but is currently limited by the fact that global shutter sensors are inferior to rolling shutter sensors in Lowlight performance and Dynamic range and cost of production, someday it might get there but not as of yet.
 
Yeah, I guess making a mechanical shutter disk for a 2/3 inch sensor is much smaller than for a super 35 sensor, I wasn't thinking about the size. Even at that I think the disk was around 1.5 inches in diameter. The LDK cameras that I've worked with had a very quiet hum from them, and every once in a while something would not down the data stream and we would see one slow down and stop.

With the following fans in most modern cameras, I wouldn't think a large shutter disk would make much noise above the fan noise, but I've never worked with an f65 and probably never will.
 
I think anything "mechanical" is on its way out. Making a mechanical shutter work perfectly in sync with the sensor's electronic shutter is not easy, and firms don't have a big incentive to research that area because electronic rolling shutter will get better and global shutter will eventually arrive.
 
Samuel H said:
I think anything "mechanical" is on its way out. Making a mechanical shutter work perfectly in sync with the sensor's electronic shutter is not easy, and firms don't have a big incentive to research that area because electronic rolling shutter will get better and global shutter will eventually arrive.
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ok, but what is the right measure for that video after being post corrected with software, in accordance with your standards?
 
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