Sony A900 noise, dynamic range and noise reduction

[Panopeeper]

I saw some surprizing results of comparisons between the Sony A900 and other cameras, like the A900's DR being a full stop greater than the D3X' and the 5DMkII's.

I set out to measure the noise and DR myself, and I soon ran into a problem: the measurement results were iconsistent, in some cases plainly contradicting each other; for example the noise measured on the raw channels separatedly is different between the channels.

It appeared that I needed better, i.e. for measurement more suitable raw files. Erik Kaffehr, a fellow poster here and a A900 owner volunteered to create the images; after some fine tuning, he delivered excellent bases for measurements.

(Btw, Erik's contribution was much greater than it is usual when I am asking someone and receiving specific raw files. In the span of several weeks he shot again and again, all together about 100 images. Those, who appretiate this report should say or think a big "thanks" to him.)

Then the surprize came: the measurement results were strange even with the best images. I had to dig deeper in the analysis (thank to Rawnalyze, this was not a problem). Some of the findings were astonishing.

I will create a much bigger essay with painfully pixel-peeping documentation of the background (I created hundreds of screen captures for this purpose), but that is a tiresome business, it will take some more time, and anyway many photographers are allergic to proofs, which are too factual; this is particularly true on these forums.

Here are the findings in condensed form:

1. Noise reduction Off, Low, Normal and High are identical from ISO 100 to 800, ON THE RAW DATA. They correspond something like NR Low @ ISO 1600.

In other words: all reviews used pre-NRed samples.

However, NR Off means almost Off with ISO 1600 (this explains the "sudden" increase of noisiness at ISO 1600).

2. The noise reduction affects mainly the red and the blue channels, much less the green. This is a very primitive noise reduction; it simply eliminates some pixel levels in the affected areas.

3. Due to the nature of this noise reduction, the very dark, noise reduced areas become darker. The consequence is, that not only the visual appearance but the noise measurement too indicates not only lower noise that it would be without NR, but that in deeper shadow, suggesting a greater dynamic range.

The magnitude of this shift is about 0.6-0.7 EV between the red/blue and the green channel. As the green channel itself is not virgin either, the shift must be even greater.

I estimate that in end effect the noise gets shifted and the DR "enhanced" by at least one full stop.

A side effect of the above is the non-linearity of the pixel values, and a WB shift in the low ranges: if the WB is correct in the "normal" ranges, it is certainly incorrect in the very dark range.

The nature of this noise reduction explaines the blotchiness as well. This will be appearant from the coming demonstrations.

Anyway, after dozens of hours squeezing these images I still can not put reliable numbers on the noise of the A900. However, I can say, that  the noise is considerable higher and the DR is considerable lower than some reviews have suggested.

[JamesA]

Anyway, after dozens of hours squeezing these images I still can not put reliable numbers on the noise of the A900. However, I can say, that  the noise is considerable higher and the DR is considerable lower than some reviews have suggested.

It's a choice.  You can buy the A900 for $3000, get the highest resolution possible in a current 24 megapixel DSLR and use post-processing noise reduction, or, you can spend $8000 for the D3x, have no choice in whether noise reduction is applied because it is in-camera and you can't turn it off.  Sony cameras, since their inception have had the highest noise but also in their class, the highest resolution. That goes back to the A100.

[ErikKaffehr]

Gabor,

Thanks for sharing information! Are you aware of any forum where users are more open to proof?

Erik

I saw some surprizing results of comparisons between the Sony A900 and other cameras, like the A900's DR being a full stop greater than the D3X' and the 5DMkII's.

I set out to measure the noise and DR myself, and I soon ran into a problem: the measurement results were iconsistent, in some cases plainly contradicting each other; for example the noise measured on the raw channels separatedly is different between the channels.

It appeared that I needed better, i.e. for measurement more suitable raw files. Erik Kaffehr, a fellow poster here and a A900 owner volunteered to create the images; after some fine tuning, he delivered excellent bases for measurements.

(Btw, Erik's contribution was much greater than it is usual when I am asking someone and receiving specific raw files. In the span of several weeks he shot again and again, all together about 100 images. Those, who appretiate this report should say or think a big "thanks" to him.)

Then the surprize came: the measurement results were strange even with the best images. I had to dig deeper in the analysis (thank to Rawnalyze, this was not a problem). Some of the findings were astonishing.

I will create a much bigger essay with painfully pixel-peeping documentation of the background (I created hundreds of screen captures for this purpose), but that is a tiresome business, it will take some more time, and anyway many photographers are allergic to proofs, which are too factual; this is particularly true on these forums.

Here are the findings in condensed form:

1. Noise reduction Off, Low, Normal and High are identical from ISO 100 to 800, ON THE RAW DATA. They correspond something like NR Low @ ISO 1600.

In other words: all reviews used pre-NRed samples.

However, NR Off means almost Off with ISO 1600 (this explains the "sudden" increase of noisiness at ISO 1600).

2. The noise reduction affects mainly the red and the blue channels, much less the green. This is a very primitive noise reduction; it simply eliminates some pixel levels in the affected areas.

3. Due to the nature of this noise reduction, the very dark, noise reduced areas become darker. The consequence is, that not only the visual appearance but the noise measurement too indicates not only lower noise that it would be without NR, but that in deeper shadow, suggesting a greater dynamic range.

The magnitude of this shift is about 0.6-0.7 EV between the red/blue and the green channel. As the green channel itself is not virgin either, the shift must be even greater.

I estimate that in end effect the noise gets shifted and the DR "enhanced" by at least one full stop.

A side effect of the above is the non-linearity of the pixel values, and a WB shift in the low ranges: if the WB is correct in the "normal" ranges, it is certainly incorrect in the very dark range.

The nature of this noise reduction explaines the blotchiness as well. This will be appearant from the coming demonstrations.

Anyway, after dozens of hours squeezing these images I still can not put reliable numbers on the noise of the A900. However, I can say, that  the noise is considerable higher and the DR is considerable lower than some reviews have suggested.

[Panopeeper]

you can spend $8000 for the D3x, have no choice in whether noise reduction is applied because it is in-camera and you can't turn it off

I'm afraid you are mixing up some issues. Although the raw data of Nikon cameras is not as raw as the Canon raw, and the difference contributes to a lower apparent noise, that is not comparable to the noise reduction carried out by the A900 on the raw data, and even less to the costomary noise reduction.

[Panopeeper]

Are you aware of any forum where users are more open to proof?

I am working on that anyway. I guess there are more posters on DPReview, who are not afraid of pixel peeping and are interested on such details.

[lattiboy]

I am working on that anyway. I guess there are more posters on DPReview, who are not afraid of pixel peeping and are interested on such details.

May I HIGHLY suggest www.dyxum.com. It's a Sony/Minolta site, but the people there are wildly open-minded and exceedingly friendly. The founder of the site has repeatedly knocked the A900 for this kind of behavior and is a D700 shooter. Seriously, I know they'd appreciate it. (not to mention a LOT of them have extensive sensor and software knowledge).

DpReview is okay.... I guess, but there are a lot of spaz/troll posters.

[BernardLanguillier]

Gabor,

Thks for the info and extended tests.

By the way, I had forgotten about that, but do you still need d3x raw files?

Cheers,
Bernard

[Panopeeper]

May I HIGHLY suggest www.dyxum.com. It's a Sony/Minolta site, but the people there are wildly open-minded and exceedingly friendly

All right, I'll give it a try; let's see how they digest the news :-)

I am not particularly interested on the Sony issues, but I am interested on all raw processing related issues. I am certainly not interested on bashing or pushing any camera or system, as I have no allegiance of any kind. My present work is a critique, not of the camera but of the professinal evaluations.

[Panopeeper]

I had forgotten about that, but do you still need d3x raw files?

Bernard, my collection of raw files contains about 4000 files (beside those tens of thousands of my own cameras, of course) - and this is still not enough to answer some questions.

I don't have *any* raw files, which are suitable for reliable measurements of the D3X noise characteristics. I do need black frames (this is the cheepo request), and special shots for measuring the noise.

I need to say at this point, that I do not think there is any big surprize in the published findings re the D3X, like re the A900. However, if I get suitable raw files, I can document my findings, i.e. publish the raw files and the evaluations. I see this as an "open review", others are free not only to criticize but to counter-evaluate the findings.

[BernardLanguillier]

I am not particularly interested on the Sony issues, but I am interested on all raw processing related issues. I am certainly not interested on bashing or pushing any camera or system, as I have no allegiance of any kind. My present work is a critique, not of the camera but of the professinal evaluations.

I agree with you on the importance of suitable camera evaluations and double checks never hurt.

Now, the fact that Sony does raw level noise reduction is not by itself a problem, and DxOMark measuring this is also not a problem. What the problem is is the fact that the impact this raw level noise reduction has on micro detail is de facto not taken into account in DxOMark results. So Sony ends up getting to good mark on DR, but not the blame on poor micro detail (or at least poorer than it could have been).

From a user point of view cleaner shadows with a bit less detail might not be a problem in itself, but they should be aware that this choice is being made for them by Sony.

Cheers,
Bernard

[lattiboy]

This is very interesting to me. I for one have been flabbergasted by the DR range of the A900. I can't imagine it being "faked" too much. I totally lack the requisite knowledge to be very helpful in this thread, all I can say is that these two shots the convinced me of the astounding DR to be had:



and



Click for larger version.

[Panopeeper]

From a user point of view cleaner shadows with a bit less detail might not be a problem in itself, but they should be aware that this choice is being made for them by Sony

From the point of this user, i.e. me, the best is to leave the decision to my discretion. I hate patronization, I can't stand when an asshole decides what the best is for me - even if that costs $5000 less tha if two assholes together would make the decision. The sad fact is, that *all* Japanese cameras show the lack of intellect in the design, and attitudes like this of Sony show, how bad this can get.

[Panopeeper]

all I can say is that these two shots the convinced me of the astounding DR to be had

While I find these shots very good, I think it is important to note, that your (or mine or anyone else's) judgement on the dynamic range of a scenery is of secondary relevance compared to the actual measurement. Normally I would ask you to please post the raw files and then we talk about the facts - but the issue is, that I could not tell the facts in case of the A900!

Anyway, my experience taught me not to rely on such subjective "DR measurement" (I for myself ceased to make such judgements). But if you want to get into a contest: my dog looks much better at ISO 800 under a 40W lamp in the kitchen than your cat under your reading lamp (I mean this is often the level of proof presented on forums).

[lattiboy]

Good point! I think I understand your original post now. How do you explain the fact that users seem to have similar experiences to me, even coming from the A700 w/ v4 firmware (which I thought had no noise control at all)? An honest question.....


PS I've noticed the A900 data has flummoxed a few different people when the RAW files are analyzed. I believe David Kilpatrick of PhotoclubAlpha was astounded that it produces images as well as it does because, "the red channel is a mess!!!".

[Bill Caulfeild-Browne]

Thanks, Gabor, for all your work and very interesting information. I enjoy reading it, though I'm really more into subjective impressions (in prints) than scientific measurements. And on that subject, I've just finished processing (with a lot of winnowing!) about 3000 a900 frames from a recent trip. What struck me most was how few shots, compared to my former equipment of another famous manufacturer, needed any highlight or shadow recovery in C1.

Please keep up the good work!

Bill

[BernardLanguillier]

From the point of this user, i.e. me, the best is to leave the decision to my discretion. I hate patronization, I can't stand when an asshole decides what the best is for me - even if that costs $5000 less tha if two assholes together would make the decision. The sad fact is, that *all* Japanese cameras show the lack of intellect in the design, and attitudes like this of Sony show, how bad this can get.

Hum... aren't you a bit over-reacting here? How many % of image quality are we talking about?

Many folks around here have been super happy about the A900 lower ISOs, even people having worked with both the A900 and D3x.

Doesn't it show that the compromise chosen by Sony is pretty good, even if not as close to best in class as some like to think?

Cheers,
Bernard

[Panopeeper]

aren't you a bit over-reacting here? How many % of image quality are we talking about?

Partonization is a mild form of terror; one can not over-react to it.

As to the % of image quality: do you mean that one should rescind a percentage of the hardware capabilities for .. for... WHAT in exchange? Perhaps it is an intentional degradation in exchange for the low price? Perhaps an A910 will be released for $200 more, the same camera but without forced NR?

Many folks around here have been super happy about the A900 lower ISOs, even people having worked with both the A900 and D3x

They should read carefully what I wrote in the initial post.

Doesn't it show that the compromise chosen by Sony is pretty good, even if not as close to best in class as some like to think?

Now, this is the point. A compromise between WHAT? A compromise presumes two or more sides of an issue; something for something. What exactly is the advantage of doing a premature noise reduction without my asking, when doing that later, at my discretion is *at least* as good? What other consideration is here beside image quality? Do Sony collect the stolen pixel levels and sell them someone?

The sensor has certain capabilities, which can NOT be enhanced, only degraded the way Sony chose to go. I am not complaining about the sensor not being good enough, but about the firmware intervening (trespassing) in the process of developing the image. What is happening is cheeting with the appearance on the cost of real quality.

There is absolutely no compromise here, only sacrifice, due to some misguided decision, just like with the A700. I wonder if Sony will do this with every new model, waiting until some customer groups are yelling loud enough.

[ErikKaffehr]

Well, yes, indeed...

My experience is that I see clearly these effects at high ISO and/or specific test targets. I never shoot really high ISO and if I do it's not in really bad light. My experience is that a lot of shadow detail can be retrieved from the KM 7D, the Alpha 700 and Alpha 900 but less so from the Alpha 100. I cannot compare with other cameras.

One of the issues I have that there is a Sony blotchiness which is very hard to eliminate. I have never seen it in other than test images, but I do these tests to find out the limitations and avoid trying to go beyond what the camera can do.

Best regards
Erik

Hum... aren't you a bit over-reacting here? How many % of image quality are we talking about?

Many folks around here have been super happy about the A900 lower ISOs, even people having worked with both the A900 and D3x.

Doesn't it show that the compromise chosen by Sony is pretty good, even if not as close to best in class as some like to think?

Cheers,
Bernard

[Panopeeper]

Following captures do NOT demonstrate the unwanted NR at lower ISOs; these are NR Off, Low, Normal and High with ISO 1600. These show, how brutal evel the lowest level of NR is, performed this way, shown on the red channel on Erik's coffee bucket.

[ErikKaffehr]

Hi,

This test image was intended to be brutal. The issue that Gabor (Panopeeper) illustrates so well is that the image with NR "off" can probably handled quite well by a late version DPP (a very good but quite different raw-converter) or by noise Ninja. The image with the high NR is beyond rescue.

Best regards
Erik

Following captures do NOT demonstrate the unwanted NR at lower ISOs; these are NR Off, Low, Normal and High with ISO 1600. These show, how brutal evel the lowest level of NR is, performed this way, shown on the red channel on Erik's coffee bucket.