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Global Shutter discussion

1bwana1
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p.11 #1 · p.11 #1 · Global Shutter discussion

Alistair1 wrote:
Interesting article from Richard at DPR on the A9III noise performance.

https://www.dpreview.com/articles/6717086661/sony-a9-iii-global-shutter-comes-with-an-image-quality-cost

Interesting read, and in alignment with expectations, and other tests I have seen. I think the salient point is that the A9III noise will be higher than other sensors when those other sensors are shot at a lower ISO than the A9III base of 250. But from ISO 250 and up, the A9III noise and DR is roughly equivalent to non global shutter sensors.

Considering that at those times when high frame rates are important, ISO is almost never below ISO 250 anyway. In fact ISO is usually much much higher than that. Therefore the actual impact on IQ with the A9III should not be significant.

The A9III is not intended to be an all around camera. It is designed to be the fastest sports and wildlife camera available. Which it absolutely sets a new standard for. It is not actually a camera that I would be interested in. In my AF system I want the best possible all around camera, in a small form factor, which the A9III or even A9II is not. But for those with a certain set of needs this first global shutter camera, and those cameras that will follow and refine the technology this will change the game.

Jan 04, 2024 at 01:04 PM

Steve Spencer
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p.11 #2 · p.11 #2 · Global Shutter discussion

1bwana1 wrote:
Interesting read, and in alignment with expectations, and other tests I have seen. I think the salient point is that the A9III noise will be higher than other sensors when those other sensors are shot at a lower ISO than the A9III base of 250. But from ISO 250 and up, the A9III noise and DR is roughly equivalent to non global shutter sensors.

Considering that at those times when high frame rates are important, ISO is almost never below ISO 250 anyway. In fact ISO is usually much much higher than that. Therefore the actual impact on IQ with...Show more →

Hi Steve,

This is not how I read the article. It seems that there will be a penalty for the global shutter at higher ISO too, because at least the current sensor doesn't use the dual gain technology that modern sensors have used for about a decade. That will be about 3/4ths to 1 stop worse high ISO performance at ISOs above 640 or so when the dual gain technology usually kicks in. Note the article talks about equal performance at ISO 250, but that is before the dual gain technology kicks in on modern sensors. Eventually gloabal shutters may be able to use dual gain technology, and have similar performance at the same ISO, but that isn't going to happen with the A9 III.

Edited on Jan 04, 2024 at 05:14 PM · View previous versions

Jan 04, 2024 at 02:48 PM

Vento
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p.11 #3 · p.11 #3 · Global Shutter discussion

That is ultimately the key message of the article.
English is not my native language, but the conclusion seems very clear to me.

"The most immediate difference in capability is that the a9 III has a base ISO of 250.
This means that you can't give it as much light as its peers with base ISOs of 100 or lower.
This is not necessarily an issue for sports photography, where maintaining a high shutter speed is much more important than the need to optimize image quality by staying at a low ISO.

What might be of more concern to sports shooters is that the high ISO performance appears to be as much as one stop noisier than its full-frame rivals, especially as you reach its highest ISO settings.
There's a noticeable softness to the 'grain' pattern in the a9 III's images too, which we suspect is the result of noise reduction being applied in the Raws.
This is in line with what we expected.
Essentially the a9 III's sensor works by having two photodiodes at each pixel: one to capture the light, initially, and the second to act as a holding buffer, that allows all the pixels to be read-out simultaneously.
This design effectively halves each pixel's capacity for light, which explains the elevated base ISO and the decreased noise performance, which brings it closer into line with the performance of APS-C cameras.
In addition, the complexity of the design means we don't get the dual conversion gain circuitry that helps improve high ISO performance on other recent cameras."

Jan 04, 2024 at 03:51 PM

1bwana1
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p.11 #4 · p.11 #4 · Global Shutter discussion

Steve Spencer wrote:
Hi Steve,

This is not how I read the article. It seems that there will be a penalty for the global shutter at higher ISO too, because at least the current sensor don't use the dual gain technology that modern sensor have used for about a decade. That will be about 3/4ths to 1 stop worse high ISO performance at ISOs about 640 or so when the dual gain technology usually kicks in. Note the article talks about equal performance a ISO 250, but that is before the dual gain technology kicks in on modern sensors. Eventually gloabal shutters may...Show more →

Could be, I realize that it doesn't have dual gain capabilities. I will wait for detailed testing with release hardware and software before solidifying my understanding of this. As I have said currently this is not a camera I would be interested in. I am more curious about what it brings to the table in the future. Right now, except for some huge unexpected gain in DR and noise to improve IQ I am not sure there are any features that would cause me to upgrade my current systems. But one never knows...

Jan 04, 2024 at 04:52 PM

Alistair1
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p.11 #5 · p.11 #5 · Global Shutter discussion

Steve Spencer wrote:
Hi Steve,

This is not how I read the article. It seems that there will be a penalty for the global shutter at higher ISO too, because at least the current sensor don't use the dual gain technology that modern sensor have used for about a decade. That will be about 3/4ths to 1 stop worse high ISO performance at ISOs about 640 or so when the dual gain technology usually kicks in. Note the article talks about equal performance a ISO 250, but that is before the dual gain technology kicks in on modern sensors. Eventually gloabal shutters may...Show more →

The main reason is explained in this sentence: "Essentially the a9 III's sensor works by having two photodiodes at each pixel: one to capture the light, initially, and the second to act as a holding buffer, that allows all the pixels to be read-out simultaneously. This design effectively halves each pixel's capacity for light, which explains the elevated base ISO and the decreased noise performance, which brings it closer into line with the performance of APS-C cameras."

Further explanation here: https://amateurphotographer.com/latest/opinion/how-does-the-sony-a9-iii-global-shutter-work/

It confirms that this technology is niche rather than universal in its application. Certainly this approach to achieving GS by splitting the available light between buffer and capture.

Jan 04, 2024 at 05:13 PM

Steve Spencer
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p.11 #6 · p.11 #6 · Global Shutter discussion

Alistair1 wrote:
The main reason is explained in this sentence: "Essentially the a9 III's sensor works by having two photodiodes at each pixel: one to capture the light, initially, and the second to act as a holding buffer, that allows all the pixels to be read-out simultaneously. This design effectively halves each pixel's capacity for light, which explains the elevated base ISO and the decreased noise performance, which brings it closer into line with the performance of APS-C cameras."

Further explanation here: https://amateurphotographer.com/latest/opinion/how-does-the-sony-a9-iii-global-shutter-work/

It confirms that this technology is niche rather than universal in its application. Certainly this approach to achieving GS by splitting...Show more →

If I understand the article correctly what you quote here is why the base ISO is 250. The reason for worse high ISO performance is the lack of dual gain conversion. They are separate effects but basically the camera will fall behind most modern cameras in noise performance both at base ISO and at ISOs above 640 or so.

Jan 04, 2024 at 05:17 PM

CanadaMark
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p.11 #7 · p.11 #7 · Global Shutter discussion

I'll read the article when I have time later, but going off the summary above, everything appears exactly as expected. The A9III will be a very expensive, extreme niche camera aimed at folks who deal with challenging LED lighting (or similar) that cannot be tamed with the tools already available to us in existing cameras, or for those needing very high RAW frame rates. Aside from those things, most people are likely going to be much better served by a different body.

The lack of dual gain is interesting to me, I hadn't considered that it might not have that as it's been a staple of Sony sensors for a long time (ever since Sony acquired the patent from Aptina) - that's too bad.

I also find it funny that at launch, Sony's Sr. Manager of Product Management claimed the IQ was even better than the A1, and not only that, he doubled down and said that there were specifically no compromises with regards to DR or ISO with the addition of the global shutter as they were able to "overcome" that challenge. At the time, those comments raised some eyebrows, and now we can see that was really a quite a blatant lie that likely got Sony more pre-orders than they would have had otherwise, so there may be some disappointed folks out there who made decisions based on those comments. It's one thing to rely on technicalities for Marketing purposes by saying something like "the best IQ of any FF global shutter camera" (knowing that they are the only one), but I'm surprised the comments made were so specific when surely he knew they were totally false.

At any rate, I'm still glad Sony brought one to market, as this will hopefully encourage more R&D into mass market global shutter sensors that can eventually perform as well as existing flagship sensors in other areas as well.

Jan 04, 2024 at 05:22 PM

Alistair1
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p.11 #8 · p.11 #8 · Global Shutter discussion

Steve Spencer wrote:
If I understand the article correctly what you quote here is why the base ISO is 250. The reason for worse high ISO performance is the lack of dual gain conversion. They are separate effects but basically the camera will fall behind most modern cameras in noise performance both at base ISO and at ISOs above 640 or so.

Not quite, the overriding reason is that half the light gets used for buffering effectively halving the SNR from the get go. The lack of dual gain exacerbates the issue at higher ISO's.

Jan 04, 2024 at 05:34 PM

RoamingScott
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p.11 #9 · p.11 #9 · Global Shutter discussion

This article was posted 8 hours ago on the Sony forum with no responses…curious 🙃

Jan 04, 2024 at 06:00 PM

Steve Spencer
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p.11 #10 · p.11 #10 · Global Shutter discussion

Alistair1 wrote:
Not quite, the overriding reason is that half the light gets used for buffering effectively halving the SNR from the get go. The lack of dual gain exacerbates the issue at higher ISO's.

Yes, that halving of the light is the reason for the higher base ISO and the resulting lower SNR at base ISO. We are saying the same thing. I just don't think you realize it.

Jan 04, 2024 at 06:00 PM

suteetat
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p.11 #11 · p.11 #11 · Global Shutter discussion

I don't know enough about engineering to understand why the second photodiode need to be on top of the sensor halving the light gathering capacity when it is only there to store charge for readout.
In stack sensor design, why can't that second photodiode be underneath the main photodiode?
My cynical side would say that Sony intentionally crippled the first global sensor generation just
so the next one already has a clear improvement path. But then again, may be there is a legitimate
explanation why they need this arrangement.

I was going to say that no big deal if the base iso is 250 as when I am shooting birds, I rarely am ever in that iso range but
the lack of dual gain is a pain.
If I am a Sony shooter, I think for my personal use, I would prefer non global shutter version of A9 iii with all the FPS it provides
as that would be more useful for me, I think.

Jan 04, 2024 at 07:19 PM

bernardl
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p.11 #12 · p.11 #12 · Global Shutter discussion

One easy way to assess the image quality of the a9IIi is to think of it as an APS-C sensor.

I have one order but may decide to cancel as the dance project for which I was considering using it will probably not happen.

Cheers,
Bernard

Jan 05, 2024 at 07:14 AM

duncang
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p.11 #13 · p.11 #13 · Global Shutter discussion

Rather than speculating one could process the A9iii RAW files and compare them with files from the R3 and A9ii or your favourite camera.

These (iso6400) were all processed in DXO PL7 with the default settings. My usual working iso range is 640-6400 so anything outside of that is not really of too much interest.

RAW files courtesy of DPReview

Interestingly the R3 appears to show more noise than the A9ii but I think the final R3 images show just a tiny bit more sharpness - is that a lens thing perhaps.

Base on these results there isn't enough difference to be noticeable unless you're pixel peeping.

I don't believe DPReview do any slightly under/over exposed studio images to be able to compare the shadow/highlight recovery on the RAW files though.

Jan 05, 2024 at 04:39 PM

snapsy
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p.11 #14 · p.11 #14 · Global Shutter discussion

duncang wrote:
Rather than speculating one could process the A9iii RAW files and compare them with files from the R3 and A9ii or your favourite camera.

These (iso6400) were all processed in DXO PL7 with the default settings. My usual working iso range is 640-6400 so anything outside of that is not really of too much interest.

RAW files courtesy of DPReview

Interestingly the R3 appears to show more noise than the A9ii but I think the final R3 images show just a tiny bit more sharpness - is that a lens thing perhaps.

Base on these results there isn't enough difference to be...Show more →

There's a low-light version of each photo. The differences are more obvious there. Here's a link I generated:

http://tinyurl.com/5n7ffahr

Jan 05, 2024 at 07:42 PM

bernardl
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p.11 #15 · p.11 #15 · Global Shutter discussion

Even the Northup, the ultimate Sony fan boys, admit that there is a 1 1/3stop gap vs competition…

Cheers,
Bernard

Edited on Jan 06, 2024 at 02:51 AM · View previous versions

Jan 05, 2024 at 09:50 PM

Alistair1
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p.11 #16 · p.11 #16 · Global Shutter discussion

bernardl wrote:
Even thé Northup, the ultimate Sony fan boys, admit that there is a 1 1/3stop gap vs competition…

Cheers,
Bernard

Exactly, whatever way the fanboys spin it, Sony's implementation of GS uses half the sensor area for buffer and the price is a halving of SNR. Further, it precludes the Aptina dual gain technology that Sony uses in all its other sensor designs. That said, for certain applications the price is worth it as it will capture images unattainable using other cameras. But the future of all photography, it is not.

Jan 05, 2024 at 11:19 PM

suteetat
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p.11 #17 · p.11 #17 · Global Shutter discussion

https://www.dpreview.com/articles/6717086661/sony-a9-iii-image-quality-dynamic-range-analysis

Looking at studio scene published on dpreview with production unit of A9 iii, what I see is that
A9 ii at iso 400 has less noise thatn A9 iii at iso 250 (more obvious on the blue square, and less difference on the grey/black square).
A9 iii noise level is in the same ball park as Z9 and a bit better than Sony A6600 at around iso 200-400 range.
At iso 6400-12800, A9ii is still ahead by a bit. Z9 is about the same and A6600 is a bit worse.

For me, the benefit from global shutter, faster FPS with raw file vs 45 vs 45MP and superior base iso performance, Z9 is still my choice for my personal use but in certain scenario, I could see A9 iii be very desirable.

PS I am a bit confused, on dpreview did they reduce the size of Z9 file to match A9 24mp resolution?
If that is the case, at least for bird and wildlife, A9 iii would be better than I expected.

Jan 05, 2024 at 11:44 PM

ilkka_nissila
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p.11 #18 · p.11 #18 · Global Shutter discussion

The widget offers different scales (see icons in the top right corner) so you can for example see the actual image pixels ("full") for each camera or compare at equal final display sizes ("comp" or "print").

Jan 06, 2024 at 01:28 AM

suteetat
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p.11 #19 · p.11 #19 · Global Shutter discussion

ilkka_nissila wrote:
The widget offers different scales (see icons in the top right corner) so you can for example see the actual image pixels ("full") for each camera or compare at equal final display sizes ("comp" or "print").

Thanks.. I did not notice widget there

Looking at actual original size, I would lump A9 iii, Z9, A6600 into the same ballpark and A9 ii ahead of the pack by quite a bit.

Jan 06, 2024 at 01:35 AM

tntcorp1
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p.11 #20 · p.11 #20 · Global Shutter discussion

imho, w/holding access to supply provides a competitive advantage, which vanished with the release of the z9.

jwolfe wrote:
This is correct. No matter how much the brain trust online seems to think they know insider stuff, there’s only two major camera sensor manufacturers (not smartphones). And it’s Canon and Sony.

You’re not gonna see a global Sony sensor in a Nikon camera for a good while. When they come up with new tech like this they keep it for themselves for awhile. But in my opinion it’s not so much about selling cameras as it is to build demand in the market. Realistically they aren’t gonna sell very many a9IIIs. But in ten years they will be selling...Show more →

Jan 06, 2024 at 01:07 PM

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