Global shutter imager

[HiTechBoys]

Hello all,

I see many discussions around freezing license plate like going for higher fps, turning off HDR, etc. I feel the fundamental issue is using rolling shutter imagers.

For fast changing scenes the camera needs a global shutter imager like the Sony Pregius series. Cameras based on this sensor are used in industrial applications for over several years. Given that rolling shutter imagers are cheap but I'm surprised that there are none global shutter dashcam. Note that the ADAS cameras for computer vision use-cases are typically having global shutter imagers.

Any thoughts?

 

[Dashmellow]

Hello all,

I see many discussions around freezing license plate like going for higher fps, turning off HDR, etc. I feel the fundamental issue is using rolling shutter imagers.

For fast changing scenes the camera needs a global shutter imager like the Sony Pregius series. Cameras based on this sensor are used in industrial applications for over several years. Given that rolling shutter imagers are cheap but I'm surprised that there are none global shutter dashcam. Note that the ADAS cameras for computer vision use-cases are typically having global shutter imagers.

Any thoughts?

I absolutely agree with you, but not everyone here is onboard with the concept of global shutters in dash cams.

There is an older thread here you might find interesting where global shutters are discussed.

Imagine if Viofio etc Videos Were This Clear

I can read all the licence plates without issue

dashcamtalk.com

 

[Nigel]

Hello all,

I see many discussions around freezing license plate like going for higher fps, turning off HDR, etc. I feel the fundamental issue is using rolling shutter imagers.

For fast changing scenes the camera needs a global shutter imager like the Sony Pregius series. Cameras based on this sensor are used in industrial applications for over several years. Given that rolling shutter imagers are cheap but I'm surprised that there are none global shutter dashcam. Note that the ADAS cameras for computer vision use-cases are typically having global shutter imagers.

Any thoughts?

You use gobal shutter when you need positional accuracy, because rolling shutter distorts the image. Dashcams don't need distortion free images.

I don't believe you can use our DOL-HDR with a global shutter camera since you can't collect more data while still reading the last lot, so any HDR would show ghost images.

I don't see any significant advantage of global shutter for dashcam use, and all the Pregius sensors are less sensitive than the Starvis 2 sensors since they are designed for industrial use where there can be plenty of light, often coming from a high brightness strobe light which we can't use with a dashcam. To freeze license plates you need high sensitivity, you need Starvis 2.

 

[Dashmellow]

I don't see any significant advantage of global shutter for dashcam use, and all the Pregius sensors are less sensitive than the Starvis 2 sensors since they are designed for industrial use where there can be plenty of light, often coming from a high brightness strobe light which we can't use with a dashcam. To freeze license plates you need high sensitivity, you need Starvis 2.

You are just rehashing the same old tired argument we've had before in the other thread I linked. As I've shown previously, Pregius 2 sensors are NOT just designed for industrial use. They are currently in use in a wide variety of high end professional cinematography cameras and CCTV cameras and their sensitivity is much higher than you are claiming. Eventually, this technology will make its way into consumer products.

 

[Dashmellow]

Here's a good example of a new 5K global shutter cinema camera from Z Cam that has very high dynamic range and sensitivity. It competes directly with the RED Komodo 6K.

Up to 16 stops Dynamic Range, rated at 14

Here's a screen shot example from the global shutter 6K RED Komodo. This is not the Pregius 2 but you can't claim that global shutter video cameras are "Less sensitive than the Starvis 2 sensors".




Another new cinema Global Shutter sensor from Canon

Canon 5.7K 60fps Full-Frame Global Shutter and 4.5K 120fps Super35 Image Sensors Announced | CineD

Canon global shutter full-frame sensor with 5.7K resolution and 60fps readout as well as a 4.5K super35 sensor announced.

www.cined.com

 

[HiTechBoys]

You use gobal shutter when you need positional accuracy, because rolling shutter distorts the image. Dashcams don't need distortion free images.

I don't believe you can use our DOL-HDR with a global shutter camera since you can't collect more data while still reading the last lot, so any HDR would show ghost images.

I don't see any significant advantage of global shutter for dashcam use, and all the Pregius sensors are less sensitive than the Starvis 2 sensors since they are designed for industrial use where there can be plenty of light, often coming from a high brightness strobe light which we can't use with a dashcam. To freeze license plates you need high sensitivity, you need Starvis 2.

I agree that higher sensitivity (shorter exposure time) is essential to reduce motion blur but capturing the entire scene at a single instant also has it's place. I feel we have already reached the limit of sensitivity by detecting single photons (SPAD) but only in ToF imagers. It will trickle down to dashcams in the future.

We have to look at how pitch, roll of car/dashcam (from road vibration), motion of cars impact the pixels as the imager is reading line by line (rolling). If the object motion is in the focal plane of the imager then it is just a simple geometric distortion (square to trapezoid) but in real world we have complex motion and this might smudge the license plate. I will try to simulate in MATLAB and evaluate how big a problem this is.

PS: I saw a video from GoPro at 240fps and still the license plate was unreadable (at low-iso)

 

[Nigel]

I feel we have already reached the limit of sensitivity by detecting single photons (SPAD) but only in ToF imagers. It will trickle down to dashcams in the future.

SPAD sensors currently consume far too much power and generate far too much heat for dashcam use.

We have to look at how pitch, roll of car/dashcam (from road vibration), motion of cars impact the pixels as the imager is reading line by line (rolling). I

I think you will find that for individual pixels there is no difference between rolling shutter and global shutter, the difference is when they are exposed, and that causes temporal distortion in the image as a whole, not in individual pixels. Rolling shutter also has the advantage of DOL-HDR, which reduces distortion on bright objects, and which I don't think can be implemented in Global Shutter sensors.

It is nice to be able to film a helicopter with the rotors turning and have the rotor blades nice and straight instead of highly curved, but for dashcam use this isn't actually a problem, so you have to overcome all the disadvantages of a global shutter sensor before they will get used.

 

[Dashmellow]

Rolling shutter also has the advantage of DOL-HDR, which reduces distortion on bright objects, and which I don't think can be implemented in Global Shutter sensors.

As I mentioned, the new global shutter sensor in the Z-Cam E2-F6 Pro has been shown to deliver up to 16 stops of dynamic range. It is conservatively rated at 15 stops (apparently not 14 stops as I said earlier). It doesn't need DOL-HDR which by comparison is a flawed band-aide gimmick technique in current dash cam implementations.

 

[Nigel]

As I mentioned, the new global shutter sensor in the Z-Cam E2-F6 Pro has been shown to deliver up to 16 stops of dynamic range. It is conservatively rated at 15 stops (apparently not 14 stops as I said earlier). It doesn't need DOL-HDR which by comparison is a flawed band-aide gimmick technique in current dash cam implementations.

You do know that the largest dashcam sensor in use today is only 3.6% the size of that camera's sensor?
So of course it is going to have huge dynamic range in comparison and doesn't need multi-exposure HDR for most purposes.

 

[Dashmellow]

You do know that the largest dashcam sensor in use today is only 3.6% the size of that camera's sensor?
So of course it is going to have huge dynamic range in comparison and doesn't need multi-exposure HDR for most purposes.

Firstly, I wasn't suggesting the we are going to see 15 stop dynamic range in dash cams any time soon but global shutter sensor technology is evolving rapidly and prices have come way down since even a year ago. Performance in high end cinematography cameras that cost tens of thousands of dollars has now been exceeded by cameras that cost only $4000 to $6000 dollars. Eventually, we will likely see global shutters replace rolling shutters in all digital cameras along with dramatic performance improvements. Sensors in cinema cameras are indeed much larger but the technology will evolve and miniaturize just the way other CCD and CMOS technology has. Also, there is finally a welcome trend toward using somewhat larger sensors in dash cams as evidenced by the A229 Pro which has a 1/1.8" sensor that measures 7.75mm x 4.36 mm at a 16:9 aspect ratio compared to the older 1/3" sensors used in older dash cams that are 5.23mm x 2.94 mm at a 16:9 aspect ratio. Eventually, we will be seeing even larger sensors used in dash cams. I believe this is inevitable.

 

[Nigel]

Firstly, I wasn't suggesting the we are going to see 15 stop dynamic range in dash cams any time soon

Based purely on the size, that big sensor should have nearly 5 stops extra dynamic range, so it doesn't seem all that good.

Eventually, we will be seeing even larger sensors used in dash cams. I believe this is inevitable

You will be arguing with the laws of physics if you try that! Definitely not inevitable.

 

[Vortex Radar]

I’m not sure if a global shutter is the best route to solve the issue. I mean sure there can be a little smudging from rolling shutters leading to plate digits that look a bit angled, but I’m not sure that makes them significantly less legible.

Usually the issues I’ve seen are tied more to things like too much motion blur due to shorter shutter speeds, blown highlights due to limited dynamic range, or simply reduced clarity farther away from insufficient resolution or perhaps lower quality lenses.

Given the choice I’m all for a global shutter, but I don’t think it would provide a dramatic improvement in terms of detail capture for dashcams.

 

[Dashmellow]

Based purely on the size, that big sensor should have nearly 5 stops extra dynamic range, so it doesn't seem all that good.

There are many other factors than size that determine dynamic range capabilities of a sensor. The Starvis 2 sensor family is certainly evidence of that even without the use of HDR.

Eventually, we will be seeing even larger sensors used in dash cams. I believe this is inevitable.

You will be arguing with the laws of physics if you try that! Definitely not inevitable

Nonsense!

There is no reason that dash cams need to be built with M12 lenses and even use the types of housings we are accustomed to. There are many other design possibilities including the potential use of C-mount pancake lenses or their equivalent. This would open up a whole realm of possibilities regarding what sized sensor could be used. Indeed there have been tiny larger sensor cameras on the market for years already such as the Sony RXO II which has a 1 inch sensor as does the Insta360 1 RS or the RS which has two and shoots 6K video.

Large sensors would be a game changer for dash cam performance.

It is always a marvel Nigel to witness the nature of the arguments you engage in. More than a year ago, in July 2022 when I suggested the possibility that one day we may see global shutter dash cams you claimed that global shutters are only used in industrial settings for machine vision where powerful strobe lights are used for illumination because such sensors are not sensitive enough . Somehow, despite all the evidence I provided back then and now about how global shutters from several manufacturers including Sony Pregius 2 are rapidly moving into the realm of CCTV surveillance cameras and high end cinematography video you are still sticking with the same misinformation.

all the Pregius sensors are less sensitive than the Starvis 2 sensors since they are designed for industrial use where there can be plenty of light, often coming from a high brightness strobe light

 

[Dashmellow]

Given the choice I’m all for a global shutter, but I don’t think it would provide a dramatic improvement in terms of detail capture for dashcams.

If we ever do see global shutters in dash cams it will be quite a few years from now when prices come down and the technology continues to evolve into the consumer space. As it is, prices are dropping rapidly and smaller sensor sizes are already available. When I first got into dash cams 13 years ago it would have been hard to imagine the performance we are seeing now both with sensors as well as chipset technology. Back then it was hard to imagine 4K, Starvis 2, wifi, parking modes, multi-channels, HDR, voice activation, cloud, and other features and capabilities in dash cams. So, personally, I wouldn't dismiss global shutters for dash cams quite just yet. It just may require some patience.

 

[DT MI]

...It just may require some patience.

Give me patience and give it to me NOW!