Definitive A900/D3X noise/ISO samples

[David Kilpatrick]

Let me explain. The Nikon is underexposing the sensor, which means less highlight detail gets clipped. It can then apply a tone curve which lifts the bulk of the data slightly higher up the scale then usual, and apply a more gentle roll off in the highlights. This would explain neatly the D300's superior highlight dynamic range measured in our review compared to the A100 (4.1 EV vs 3.3 EV).
--
Andy Westlake

This is fairly old now and probably does relate to the D300/A100, but the strategy with the D3X is to do this and then restore the normal exposure! Really, the D3X is underexposing an ISO 200 native setting (ISO 160) or would be if the camera was set to 200/160. Instead, they set it to 100. I can not compare the D300 and A100 now, the present situation is not identical, but the methods are the same - Nikon is manipulating sensor gain, ISO ratings, and post-processing curves to maximum effect. The trade-off in the D3X is a loss of highlight roll-off, no matter what the D300 had. Sony is now using an in-camera curve which lifts the data values. I don't actually think Andy got it right because unlike RAW Developer, the converters he was using did not give access to the tone curve used when converting the raw. So he was not seeing some hidden processing during raw conversion (out of the camera).

David

[stevecim]

With my totally untrained eye, the biggest differance I see is all the tiny red pixels in the black areas.
Yellows, green,blue, red and light gray look OK, but blacks, dark grays, dark greens get blown away with all the red dots, the a350 gets the red dots in black areas and black dots in red areas

But that's just my newbie view

Stephen

[j_p_p]

check this RAW comparison :

http://www.imaging-resource.com/PRODS/E5D2/E5D2RAW.HTM" onclick="window.open(this.href);return false;

[mdcromer]

Don,

What David is claiming is that you should be able to get similar results from the Sony by turning down the ISO and then underexposing 1, 2, 3 or more stops, and then bring them up in post processing.

He is claiming that this is the strategy that Nikon is using (less on-chip amplification and more tone curve RAW conversion amplification).

Makes perfect sense if the on-chip amplification is the source of the noise issues.

Maybe reshoot one of the prior tests at ISO 800 on the Alpha 900 and underexpose 3 stops, then lift in post? That will mean a lot less on-chip amplification and a lot more RAW convertor amplification.

I think Emil was recommending this with the Alpha 900, although he went as far as to recommend shooting at the base ISO, and getting all your ISO boosting in post.

[douglasf13]

David K, this is a very, very pertinent finding that should be explored. It echoes Iliah Borgs findings. I can't wait to see some samples of the a900 win the D3x curve. Good work.

Sonolta, your machine gun posting hasn't shown that you understand the concept David is trying to explain. He is essentially saying that Nikon uses less amplification in the camera than the A900 and boosts with a tone curve in the RAW processing. Like I said in an earlier post, this is a trade off with the nice a900 highlight roll off.

[David Kilpatrick]

Don,
What David is claiming is that you should be able to get similar results from the Sony by turning down the ISO and then underexposing 1, 2, 3 or more stops, and then bring them up in post processing.
He is claiming that this is the strategy that Nikon is using (less on-chip amplification and more tone curve RAW conversion amplification).

To underexpose the Sony, with the internal camera workings as they are now, might produce more noise. There is some argument for just using the Sony at ISO 800 max, and underexposing if you want 1600 or 3200, then pulling the result back in raw conversion. I know that underexposing ISO 400 by -1 or -2 works well but that only gets you to 1600 max.

Nikon's approach is turn the 'read' values down by 2/3rds of a stop (presumably by clipping the shadows, discarding low values), flatten the midtone/shadow boost given later in the pre-raw processing, and allow 1 stop more exposure by assigning a lower ISO rating for metering purposes. Nikon ISO 100 = Sony ISO 200 when both are compared for highlight exposure not shadows. This results in very clean noise-free data to which a raw conversion curve can be applied safely. They may also be doing some NR to the pre-raw data.

If you overexpose the Sony by one stop, then pull in the result in raw processing, you might get some of the benefits but you can never imitate the total removal of low value shadow data which is responsible for so much noise.

It is easy to see why this works well at low ISOs and rather harder to see how it is benefiting high ISOs. Tests already show that Sony is overstating high ISO values in the A900, and practical results show that treating 6400 as if was really 3200 can transform the result. That would be fine if the Nikon implementation did not go up to 6400 as well, but it does. Nikon is doing more useful processing somewhere along the line, or their speed range would be 50 to 3200 with no boost to 6400.

David

[01af]

What David is claiming is that you should be able to get similar results from the Sony by turning down the ISO and then underexposing [...] He is claiming that this is the strategy that Nikon is using ...

No, just to the contrary! David said, Nikon's strategy is to deliberately over-expose by approx. 2/3 of an f-stop. This naturally will reduce noise in the dark tones and midtones but will also cause more clipping in the highlights.

Furthermore, raw data always needs a gamma curve to be applied, or the midtones will look way too dull and dark (no matter whether you're under- or over-exposing a bit). Nikon's strategy is to cut away the noisy darkest tones (which they can afford due to the over-exposure) and then to leave lifting the midtones to the software after demosaicing (which will distribute the remaining noise, similar to a dithering algorithm).

Sony's strategy, if I understand correctly, is to give less exposure, to do no shadow clipping, and then to apply some of the midtone lifting on-chip, before demosaicing. The benefit is finer tones across the tonal range, a wider dynamic range, and a film-like highlight roll-off, at the expense of more noise.

We can also put it this way: the analog value of what ends up in the final RGB image as a midtone gray, i. e. RGB (128/128/128), is lower in the Sony sensels and higer in the Nikon sensels, before A-to-D conversion. Both approaches do make sense; both have their strengths and weaknesses. The problem (for Sony) is this: to fully appreciate the strengths of Sony's approach, it takes looking at prints, not pixels. However, pixel-peepers prevail these days, so most people don't understand how sensible Sony's approach really is.

-- Olaf

[Greg Beetham]

I'm afraid I still don't get it, if Nikon is over-exposing by 2/3ish- stop....how come they are using faster shutter speeds?? with the same settings everywhere else??
Greg

[Greg Beetham]

I'm just thinking out loud here..... what's the chances of Nikon being able too vary the gain selectively across the sensor?? such as potentially overexposed areas receiving less amp gain??
Greg
ps. It's Christmas morning here, now, so season's greetings everyone.

[Greg Beetham]

There is also the auto darkening pixels in a welders helmet visor (the impact of photons causes the darkening, the more powerful the photons the darker), if there was maybe a way of using that technology..or a variation of it in the microlenses....
Greg

[j_p_p]

But now the question, since the machine is out already for a couple of months ...is what Sony is thinking about this and when (1 year ???) / if they will do something Firmware wise to improve this ...

[j_p_p]

yeah....but they improved the a700...so they can take the "know how" they adquired, and apply it on the a900 i think...that considering that the a900 sensor is kinda similar in "architecture terms" to the a700 ... wich may be or not...

The a900 is already out for a couple of months, and Sony must be aware that the 2 main complaints about it is the first of all the noise and the tendency to underexpose pictures.

Of course many complain of the lack of liveview but that is not fixable in firmware

[j_p_p]

What's a bit funny about this is the fact that Sony claimed that a700 V4 was a result of a900 development. It's does seem just a wee bit peculiar, eh?

-Sonolta

not "peculiar" but really more "definetly weird" than anything else

I wonder if some people "with Connections" already contacted Sony about this and / or have any idea on what they may be working in... I'd expect that with the release of the Canon 5d mk II and now of the D3x , Sony might have already come forward with some anouncement, but...till now, nothing

[alphaomega]

I refer to the exchange of views above between J-P-P- and Sonolta on the A900 noise and underexposure issues and the fact that as j-p-p- wrote:

What's a bit funny about this is the fact that Sony claimed that a700 V4 was a result of a900 development. It's does seem just a wee bit peculiar, eh?

I must admit that I was bemused when the noise patterns in the A900 as compared with the D3X were revealed in this important thread. I was interested to read a reply by A1000 to an insert I made in the "What would be the next logical innovation for Sony DSLRs?" thread. Here is the reply and my original insert:

A700 replacement will not use back iluminated CMOS. The manufacturing process is very complex, so it will appear in the small sensors first. Sony will not be able to improve the larger CMOS sensitivity for a while, except by making the spaces between the photosites smaller. Back illumination and high speed shutter as a part of the CMOS will be the new major innovations.

Sony needs to devote more software resources to the JPEG engine, etc. It seems tahat their software people were all concentrating on the Blu-Ray technology, Playstation live, content downloads, etc. and the DSLR firmware problems were totally ignored. Sony certainly has superb resources in this area, but unfortunately has other priorities; that is why Canon and Nikon beat them in this area.

It's only matter of time and Sony will catch up. It however takes too long. A700 V4 took so long to implement; A900 JPEG engine is so poor, etc. Hope they start cooperating in this area with Nikon. Sony's software resources were apparently allocated to where they see more profits. They get their market share via proper marketing and some advanced technology, but they don't have the resources allocated to solve simpler tasks like proper JPEG engine.

alphaomega wrote:
I am coming back to my contributions above (earlier today) to re-state my case for an updated A700. This is the oldest DSLR in Sony's current line-up and surely due for an upgrade in 2009.

A1000 wrote above Back iluminated sensors will come first with smaller sensor sizes.Maybe that will start in the A700 upgrade.

I would hope that the rumoured Sony 16 Mp sensor will display a stronger signal to noise ratio than the current 12 Mp Exmoor APS-C sensor thus enabling Sony to produce a sensor that will blow the 50D out of the water at lower ISOs (up to and including ISO800). That will do me for starters, particularly if LV is incorporated without reducing the A700 OVF size or quality.

For the benefit of FF supporters I believe Sony will then double up and produce a successor to the A900 with 32 Mp and even better IQ, resolution and low noise. Nikon will follow and maybe leave Canon with a problem unless they are themselves preparing to join in this continued Mp race without an obvious end.

I am not a professional photographer and is far behind the likes of DK & Sonolta (to mention just two contributors) in photographic knowledge and experience, but I do belive in the A900 concept of a superior photographic tool optimised for a particular purpose as all tools are a compromise between competing demands and constraints. My hope is that the A700 replacement will be optimised for the same segment as the A900 is trying to cover FF (but with LV - thanks).

Now I am not a privy to the "inner workings" of Sony and their allocation of software expertise. I do not know to what extent A1000 is on the inside either, but it is disturbing if the DSLR division is so depending on "outside" software writing capabilities that they may be forced to release products well knowing that they will be found wanting against major competitors such as Nikon and Canon as demonstrated throughout this thread and perhaps not knowing when they will be put in a position to issue the necessary upgrades.

[tbcass]

Pako,

The sony files are underexposed, it is not surprising that the noise is "painful".

Also, a touch of color NR will do wonders. I prefer to leave the luminance noise in place though.

Got the A900 last weekend (I borrowed from the Adorama Rentals) and used it for a couple of small gigs and I went to the Brooklyn Botanical Garden (the greenhouse is my favorite place during winter time...)
JPGs @ 400 ASA are really bad, reminds me to the A100 JPGs -since I only needed 6MP for those gigs, noise wasn't that notorious.

Painful, yes...

Funny, I use the A100 and find the noise at iso400 more than acceptable. They make fantastic prints. Maybe you suffer from Pixelpeekitus. My iso400 available light shots at a recent wedding got rave reviews.