Global shutter sensors, the next "revolution" in photo technology?

[Bob123]

Is there any sensor specialist out there who can answer my questions/thoughts about global shutter:
1/ When we will finally get sensors with real global shutter?
2/ Did this means that we can get rid of the mechanical shutter, or will there still be reasons to keep a mechanical shutter? (My understanding of global shutter means no more mechanical shutter.)
3/ When will it be possible to synchronise flash with electronic shutter? (Not yet possible with Sony's A9 almost global shutter!)
4/ This should mean that we will not need HSS anymore, right? How much less power will need our outdoor flashes?

Thanks

Edited August 28, 2018 by Bob123

[Sly]

Hi Bob123, 

I am not a detector technolog, but I use and characterise detector for science application. So my comments are just reflection and gesses, not coming from a global shutter cmos expert. 

1/ Apparently the technologie is there already https://news.panasonic.com/global/press/data/2018/02/en180214-2/en180214-2.html . 

However the fact it is still not in current mirrorless camera means that the technology is not completely ready. When ? I have no idea. But it is getting more and more concrete. 

2/ My guess is that it will depend on how good will work the global shutter. If it is working good enough so there is no light leek in any photographic condition, mechanical shutter should disappear. It is only a guess. 

3/ The idea of using flash is that, the flash light is making the exposure on the subject, not the shutter speed. With mechanical shutter you have to flash after the shutter is fully open and before the shutter start to close otherwise you will see the shutter shadow on your image. The more you shorten your exposure, the more significant become the shutter time (the shutter-time/exposure-tim ratio increase).  The global shutter promise that this electronic shutter time is near zero so no more lag, but still your burst of light has to be synchronise to the exposure and as to be shorter or same time than the exposure if you want the photo subject to be expose by your flash only (and not shutter speed). It will still be a limiting factor. How fast they synchronise ? I have no idea :) 

4/ c.f. limiting factor expose in 3/. I doubt they can synchronise flash and exposure at 1/8000th of a second (even with global shutter), so still HSS will be necessary in these cases. In HSS the photo subject exposure will be set by the flash burst and the exposure time  (and not flash burst only).

 

I reached the limit of my knowledge to add concrete numbers to it. 

Sly

[Bob123]

Reply From "akkual" https://disqus.com/by/akkual/  09.09.2018
https://www.fujirumors.com/sony-brings-global-shutter-technology-to-aps-c-sensors/
 

Quote

 

1/ when we have a technology that can read/reset the whole sensor at once
2/ yes, it means exactly that
3/ It would be already possible in lower shutter speeds than the sensor readout speed is, e.g Sony A9 should be able to sync to flash with ES at speeds like 1/60s. It has not probably been implemented as quite useless feature?
4/ yes

The problem is that ES works as follows:
1) the pixels need to be resetted for the new exposure to begin. The resetting starts from top/bottom of the sensor
2) from the resetting of a pixel, the pixel needs to be read after the shutter speed time has passed (e.g. 1/32000s later)

So the exposure time is in between resetting and reading. Typically, these are done a row at a time with electronic shutter. Hence, if the readout (or resetting) speed is slow, moving objects will get rolling shutter effect.

Currently, A9 has something like 1/125s of readout/reset speed (typically, reset speed may be faster, but as we want the same exposure time for all rows, the reset speed will be limited to the same speed as readout).

This means that it takes 1/125s for the ES to reset whole sensor, and once it has resetted the 1st line, it will at fastest 1/32000s later start reading the 1st line.

For us to get true global shutter for photography that would eliminate mechanical shutter, we would need at least 1/4000s - 1/8000s or faster reset/readout speed - or some new technology that allows us to reset, record, and locally store the readout to the sensor via global trigger (so that we do not need to swipe through the whole sensor).

I am actually pretty sure that this sensor does not have enough fast operation for photography yet, but it very well can have enough fast for most of video use. Hence, it will get non-distorted frame of fast moving objects.

 

 

Edited September 9, 2018 by Bob123

[Bob123]

From "Phanter" https://disqus.com/by/disqus_9vPPegs5Cx/ 09.09.2018
in reply to "akkual" on https://www.fujirumors.com/sony-brings-global-shutter-technology-to-aps-c-sensors/
 

Quote

 

You are correct on many things. But global shutters work differently. They don't just have fast readout, they have "storage pixels".
The camera starts readout all at once, by a global reset. The "capture pixels" are connected to the "storage pixels". Then at the end of the exposure the connection between capture and storage pixels is cut off. And the storage pixels are read out normally.

This way the shutter is truly global. But you can also easily see why this technology has DR disadvantages, since the "storage pixels" will never be as large, as a combined storage capture pixel