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Simultaneous dual gain sensors


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I’m curious why simultaneous dual gain sensor architectures a la the Alexa Alev III aren’t more common in smaller cameras.  This allows a low and high ISO signal to be combined for one HDR image. It seems that in ten years most cameras still can’t match the Alexa for sheer video dynamic range, yet CMOS sensor technology has obviously evolved in many ways.

Is there a limiting factor like size/heat, a patent, or maybe otherwise?  Perhaps it’s just that the average consumer is more interested in increased resolution? We now are seeing the switchable dual gain architecture used more, but I’m not aware of lower end cameras using simultaneous dual gain. 

Related info:

https://www.arri.com/en/learn-help/technology/alev-sensors

 

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I think I read that the Ursa mini 4.6/pro/G2 use the same approach but with two 11 bits signals rather than 14 from the Alexa, but I m no expert.

I would not be surprised if the power consumption/heat is greater, or if the cost of the sensor is not higher.

 

But modern Dual gain architecture is something different if I understand it properly, it was developed by a third party company, and they licence the technology to sensor manufacturer and I think it s both a software and a hardware thing, it I think it map the dynamic range in a different way, you loose in the highlight but gain in the shadows. I think the sensor only do a single readout with this technology.

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3 hours ago, Patrick B. said:

I’m curious why simultaneous dual gain sensor architectures a la the Alexa Alev III aren’t more common in smaller cameras.  This allows a low and high ISO signal to be combined for one HDR image. It seems that in ten years most cameras still can’t match the Alexa for sheer video dynamic range, yet CMOS sensor technology has obviously evolved in many ways.

Is there a limiting factor like size/heat, a patent, or maybe otherwise?  Perhaps it’s just that the average consumer is more interested in increased resolution? We now are seeing the switchable dual gain architecture used more, but I’m not aware of lower end cameras using simultaneous dual gain. 

Related info:

https://www.arri.com/en/learn-help/technology/alev-sensors

 

The Sigma fp will have simultaneous dual gain sensor for HDR. I believe the Z-Cam also offers this feature,  though it does not work well because of a slow sensor readout. 

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3 hours ago, Patrick B. said:

I’m curious why simultaneous dual gain sensor architectures a la the Alexa Alev III aren’t more common in smaller cameras.  This allows a low and high ISO signal to be combined for one HDR image. It seems that in ten years most cameras still can’t match the Alexa for sheer video dynamic range, yet CMOS sensor technology has obviously evolved in many ways.

Is there a limiting factor like size/heat, a patent, or maybe otherwise?  Perhaps it’s just that the average consumer is more interested in increased resolution? We now are seeing the switchable dual gain architecture used more, but I’m not aware of lower end cameras using simultaneous dual gain. 

Related info:

https://www.arri.com/en/learn-help/technology/alev-sensors

 

Certainly in the audio world then the dual A/D converter patent by Zaxcom has been a real roadblock 

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33 minutes ago, DBounce said:

The Sigma fp will have simultaneous dual gain sensor for HDR. I believe the Z-Cam also offers this feature,  though it does not work well because of a slow sensor readout. 

I think the z cam WDR mode uses two shutter speeds, instead of two gains. Thats why you get strange motion artifacts. It also has dual native ISOs in additionb but no simultaneous dual gain.

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1 hour ago, IronFilm said:

Certainly in the audio world then the dual A/D converter patent by Zaxcom has been a real roadblock 

Interesting. I’m mainly an audio guy but wasn’t aware of that. 

1 hour ago, KnightsFan said:

I think the z cam WDR mode uses two shutter speeds, instead of two gains. Thats why you get strange motion artifacts. It also has dual native ISOs in additionb but no simultaneous dual gain.

That was my understanding too. It just takes two different exposures in quick succession thus the worse rolling shutter performance.  Doesn’t RED do this too in their special WDR modes?

As opposed to Arri where it seems that both exposures happen together. 

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35 minutes ago, Patrick B. said:

Interesting. I’m mainly an audio guy but wasn’t aware of that.

That is why the standard version of the Sonosax SX-R4+ can't be sold in the USA! And they had to make a special (read: crippled) version for the USA.

 

Zaxcom patents/lawyers have meddled in lots of other ways too, such as with the Tascam DR10, Audio Ltd A10, or the Lectrosonics PDR, or harassing Newsshooter.com

And we're holding our breath to see if Zaxcom responds legally against the new MixPre Gen 2 or the Zoom F6

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38 minutes ago, Patrick B. said:

That was my understanding too. It just takes two different exposures in quick succession thus the worse rolling shutter performance.  Doesn’t RED do this too in their special WDR modes?

It's a nitpick, but it's not exactly worse rolling shutter. It's that two shutter speeds are measured simultaneously, so the motion blur isn't natural. It's just like overlaying a shot with 1/48 shutter with a 1/200 shutter; the motion blur is like a "half frame" compared to the rest of the image, because you only get a blur from the 1/48 version.

There is also a Low Noise mode, which uses a longer readout time to get more precision and thus improve noise at the cost of rolling shutter, which doesn't have the motion blur artifact, but does have increased rolling shutter.

13 minutes ago, IronFilm said:

And we're holding our breath to see if Zaxcom responds legally against the new MixPre Gen 2 or the Zoom F6

I was just going to ask how the F6 related to Zaxcom's patents. I wonder if Zoom and/or Sound Devices plans to challenge the patent, like some other companies we talk about a lot here.

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22 minutes ago, KnightsFan said:

I was just going to ask how the F6 related to Zaxcom's patents. I wonder if Zoom and/or Sound Devices plans to challenge the patent, like some other companies we talk about a lot here.

One of the (many) problems with the patent system is that the patent holder has the full power of the government behind them to enforce it, and if you think their patent is based on bullsh*t then you have a very tough, very expensive, uphill battle to be free of their patent.

So if you're an extremely small and niche company such as Sonosax then it makes no sense at all to even try to fight Zaxcom just to be able to sell your product in one particular market, even if you feel their patent was granted on the most flimsy of reasons. 

Even Tascam, who is a much much much bigger company than Zaxcom, still saw no point in trying to fight it out with Zaxcom because their patent only impact just one product that Tascam makes, which represents but the tiniest fraction of the overall company. Is much easier for them to just tweak the design so the patent can be ignored than to fight the legal case. 

Seems though that one company has finally said enough is enough, and is going to battle it out, when Zaxcom picked a fight with Lectrosonics. Am sure all the other companies are just holding their breath to see how this turns out, if Lectrosonics wins, expect heaps of firmware updates overnight for all the various recording/transmitting products to be fully enabled such as from Audio Ltd and Deity. 

 

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1 hour ago, KnightsFan said:

It's a nitpick, but it's not exactly worse rolling shutter. It's that two shutter speeds are measured simultaneously, so the motion blur isn't natural. It's just like overlaying a shot with 1/48 shutter with a 1/200 shutter; the motion blur is like a "half frame" compared to the rest of the image, because you only get a blur from the 1/48 version.

Ahh ok that makes sense. 

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  • 7 months later...
On 9/16/2019 at 12:12 PM, KnightsFan said:

It's a nitpick, but it's not exactly worse rolling shutter. It's that two shutter speeds are measured simultaneously, so the motion blur isn't natural. It's just like overlaying a shot with 1/48 shutter with a 1/200 shutter; the motion blur is like a "half frame" compared to the rest of the image, because you only get a blur from the 1/48 version.

Which is why they suggest you use 1/200 shutter speed or higher, so these effects aren't noticed. If you use a high shutter speed it's actually a pretty good feature.

Magic Lantern also has a Dual ISO feature also. It reads out alternating lines at different ISOs and combines them into one image.

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8 hours ago, Patrick B. said:

I’m really curious to see if Canon’s new DGO (Dual Gain Output) technology in the C300 mark III will finally crack the DR monopoly that Arri’s ALEV III dual gain architecture has had.

Hasn't Blackmagic tried the dual gain approach as well?
 

1 hour ago, ntblowz said:

with DGO it outperform the C500 II on DR


I bet there are a few C500mk2 owners who wish they'd got the cheaper C300mk3 instead!

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15 minutes ago, IronFilm said:

Hasn't Blackmagic tried the dual gain approach as well?

Yeah good point. I believe that’s true for their Fairchild sensor cameras. Makes me wonder why those didn’t quite reach Alexa level DR (although the UMP is pretty high). I always thought the dual gain approach was the sole reason Arri had some of the best DR.

 

2 hours ago, tweak said:

Which is why they suggest you use 1/200 shutter speed or higher, so these effects aren't noticed. If you use a high shutter speed it's actually a pretty good feature.

Magic Lantern also has a Dual ISO feature also. It reads out alternating lines at different ISOs and combines them into one image.

I picked up a used E2 so I need to compare WDR mode. I saw someone post a dark interior shot in the Z Cam FB group using that mode where the window was able to be kept from blowing out. It seemed impressive. 

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7 hours ago, Patrick B. said:

I picked up a used E2 so I need to compare WDR mode. I saw someone post a dark interior shot in the Z Cam FB group using that mode where the window was able to be kept from blowing out. It seemed impressive. 

If 180shutter isn't needed (or you don't have fast moving camera of subject then you can actually use 180shutter), it's a really good tool, the extra DR is noticable, but too be honest most of the time I just shoot in regular Prores 48fps Zlog2 which still has great DR if you ETTR properly. I've also gone back to using my EOSm for MLraw, which mixes great with the Zcam colour science. I have a GH5 as well which is still a very good camera, but I find it much harder to match it to the other two.

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20 hours ago, Patrick B. said:

I’m really curious to see if Canon’s new DGO (Dual Gain Output) technology in the C300 mark III will finally crack the DR monopoly that Arri’s ALEV III dual gain architecture has had.

C300 MK III DGO only scored 12.8 stops using ARRI standard.

https://***URL not allowed***/canon-c300-mark-iii-lab-test-pre-production-dynamic-range-rolling-shutter-and-latitude/

For reference:

C300 MK II: 12.3 stops

C500 MK II: 13.1 stops

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45 minutes ago, androidlad said:

C300 MK III DGO only scored 12.8 stops using ARRI standard.

https://***URL not allowed***/canon-c300-mark-iii-lab-test-pre-production-dynamic-range-rolling-shutter-and-latitude/

For reference:

C300 MK II: 12.3 stops

C500 MK II: 13.1 stops

Yeah, just read that!  I’d be lying if I said I wasn’t disappointed.  Not that I’m gonna pick up a C300 MK III.. but I’d just like to think after 10 years someone else can match an ARRI for DR ha ha.  I guess at this point everybody is pretty close though.

So I guess ARRI’s implementation in the ALEV III is very special.. not to say they are the same approach since they don’t have the split, dual-pixel design.  But I thought surely that using two separate exposures would yield even greater DR.  Puzzling...

5 hours ago, tweak said:

If 180shutter isn't needed (or you don't have fast moving camera of subject then you can actually use 180shutter), it's a really good tool, the extra DR is noticable, but too be honest most of the time I just shoot in regular Prores 48fps Zlog2 which still has great DR if you ETTR properly. I've also gone back to using my EOSm for MLraw, which mixes great with the Zcam colour science. I have a GH5 as well which is still a very good camera, but I find it much harder to match it to the other two.

good to know.  yeah I can see where it would be a special use feature that I might not even want all the time.

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