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Author Topic: How are dynamic range and sensor size related?  (Read 4109 times)

dilbert

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Re: How are dynamic range and sensor size related?
« Reply #15 on: May 08, 2012, 06:26:26 AM »
DR has more to do with the design of the sensor circuitry away from the pixel. The analogue to digital converters, for example. Interference in the circuit from other circuits or the camera. DR is all about quality.

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Re: How are dynamic range and sensor size related?
« Reply #15 on: May 08, 2012, 06:26:26 AM »

Canon-F1

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Re: How are dynamic range and sensor size related?
« Reply #16 on: May 08, 2012, 06:35:24 AM »
DR has more to do with the design of the sensor circuitry away from the pixel. The analogue to digital converters, for example. Interference in the circuit from other circuits or the camera. DR is all about quality.

nice platitude ... ;)...

if everything at the sensor/photosite level works optimal then the ADC is the factor that determines the achievable DR.

but i guess there is room for improvement on the sensor level.
for example the filters can be improved, the substrate can be improved, coatings can be improved, the fill factor can be improved, gate structure can be improved.

all things that affect quantum efficiency, well capacity. 
« Last Edit: May 08, 2012, 06:45:52 AM by Canon-F1 »
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KarstenReis

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Re: How are dynamic range and sensor size related?
« Reply #17 on: May 08, 2012, 06:43:58 AM »
Roger from lensrentals wrote an article explaining some of this stuff.

http://www.lensrentals.com/blog/2012/02/sensor-size-matters-part-2

jrista

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Re: How are dynamic range and sensor size related?
« Reply #18 on: May 08, 2012, 12:39:31 PM »
Aye, the 7D's read noise is quite a bit lower (although not nearly as low as an Exmor sensor, which ranks in at 2-4e-). I think the 7D has around 17-18e- read noise at ISO 100, which is roughly HALF that of the 5D III. I am honestly rather baffled by the read noise of the 5D III sensor. For all the progress that is apparently possible in the area of read noise, and how important it is to maximum DR, it really surprised me to see it JUMP from the 5D II's 27-28e- to over 33e-.

Another elementary question: Can there possibly be any benefit of increased read noise? I assume not, but it is very odd that it would increase on the 5DIII over the 5DII. Also, is read noise the same as visible noise in an image? If so, how does the 5DIII manage to do well at high ISO in terms of noise visible in the image when read noise is so high?

Its more than just "read" noise...that is why I tried to use the term "electronic noise". There are a whole variety of forms of noise in an electronic system, including read noise, but also dark current noise, thermal noise, differential noise (due to inconsistencies in the efficiencies of individual transistors for each photosite), etc. There are ways of mitigating each of these forms of noise. Canon sensors only seem to do a basic form of CDS, or correlated double-sampling, which mitigates a certain amount of dark current noise. Sony sensors, on the other hand, have a variety of ways of mitigating most types of electronic noise, which is why their sensors perform better.

As for high ISO, I am not sure of the exact mechanics, but I believe the black point rises as you increase ISO (thanks to Canon's use of a bias offset of 2048, signal actually starts at -2048 and rises from there). You effectively lose DR on both ends, shadows and highlights, as ISO is increased. By ISO 400 or so, it seems the black point is high enough that it starts above the electronic noise floor, meaning the only really significant form of noise left is photon shot noise (a matter of physics and therefor beyond our control.) Sony sensors, it seems, don't have a bias offset, so they are pretty much always starting from the same point (zero, effectively), and they lose DR on the highlight end of the scale as you increase ISO. Their shadow DR seems to be pretty static. 

Quote
Anyway, back to the bind. My landscape, macro, and astrophotography could really benefit from lower noise and better shadow recovery. Particularly my landscape work, which I haven't done much of over the last 8 months, and none of whatsoever this year so far. I always find myself needing to push shadows around, and they have never really looked all that good, on any of the Canon cameras I've used (450D, 7D, 5D II). My options are either to add Nikon to my overall kit, deal with a menu system which irks me and body ergonomics that don't fit my hands right...deal with what I've got...or deal with what Canon has to offer. None of those options really solve my problem well, and the only one that solves it at all will also cost thousands of dollars for a new body (D800) and a couple lenses to cover the bases...such as a 14-24 and maybe a 24-70. Thats about $7000 worth of gear...something I can't afford at all right now (I can't even afford a 5D III, which I expected to list for around $3000, some $200 over budget already.)

Have you considered a D5100 or D7000? They'll get almost as much DR as a D800 for a fraction of the cost.

Well, for landscapes, I really want that extra resolution. A low resolution of 12mp really doesn't interest me much, and I was hoping the 5D III would land with 28-32mp. The D800E with 36.3mp and its incredible DR is about as close to the holy grail of landscape photography as I think it can get these days. I'd much prefer if Canon could reciprocate with their own megapixel/DR monster, though.
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jrista

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Re: How are dynamic range and sensor size related?
« Reply #19 on: May 08, 2012, 12:43:54 PM »
Hi,
    I believe the sensor technology gap between Sony/Nikon and Canon is not that big. IMHO,
the Canon sensor are just as good as Sony/Nikon sensor... the different is how they handle the signal and noise.

     Here is what I think:
   Canon RAW file include the bias signal which mean all the noise (positive and negative) are include in the
data, but Nikon RAW files somehow do not record the bias signal... I think may be Nikon filter out all those data, so only those information (signal and noise) that are above bias level are recorded in the image.

    As a result, Nikon sensor perform better at lower ISO as noise below the bias level are not recorded in the image. But as ISO increase, those noise lower than the bias level are now above the bias level, so they are recorded in the image. So at higher ISO, performance of Nikon sensor are now on par with Canon sensor.

   Now if you take the above and look at all the review on Nikon D800 and Canon 5D3, it does seem to be the case: at low ISO Nikon D800 perform better than Canon 5D3, but at high ISO, Canon 5D3 perform better due to a larger pixel size (higher signal) compare to smaller Nikon D800 pixel size (lower signal).

   Just my $0.02.

   Have a nice day.

Nikon cameras do not include a bias offset for the simple reason that the sensors they use now do not have enough noise to warrant it. Sony sensors produce excessively low noise around the 3e- level. Its pretty difficult to get much lower than that. SoNikon simply doesn't need a bias offset because there effectively isn't any noise to interfere with the image signal. The reason noise at higher ISO is on par with Canon is because the very vast majority of that noise is photon shot noise, resulting from the physical nature of photons, something we have no control over in the first place. Once shot noise dominates, there really isn't any difference between one brand or another...its all just physics.
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jrista

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Re: How are dynamic range and sensor size related?
« Reply #20 on: May 08, 2012, 12:47:17 PM »
i wrote it in another thread.

photographic dynamic range = full well capacity / read noise.

that´s it in short.
i also wrote that canon imo has to work on it´s analog digital conversion to get better DR.
the cleaner D800 signal and the higher DR seem to affirm that.

increasing the full well capacity while having smaller pixel is a hard task so i guess sony has managed to reduce the read noise siginficantly and increased the quantum efficiency.

i have not read the whole amout of writing above so i guess it was said already. :)


so... that said i read from various sources that most of the noise today (in low iso images) from digital SLR cameras is not read noise but photon statistic noise. you can influence photon statistic noise only one way... collecting more photons.
and that would mean higher full well capacity and better quantum efficiency.

but im not sure if its correct that read noise can´t be much improved these days.

Sony definitely has better ADC. The difference between Sony ADC and Canon ADC is that Sony's is on the sensor die in Exmor sensors, using CP-ADC or column-parallel ADC. This gives them a lot of power to control the read noise on a per-column basis, helping eliminate forms of fixed pattern noise. Canon's ADC is off-die in the image processor (Digic). It is also parallelized, I believe there are 8 read channels per DIGIC in the 1D X and 5D III, and 1 ADC per channel. Canon's ADC's have to work at a higher frequency since each one is processing more pixels than Sony's on-die CP-ADC, which introduces more noise. They also don't have the ability to filter out column-level noise like Sony does, so their ADC's convert FPN into each ADU as well.
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NormanBates

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Re: How are dynamic range and sensor size related?
« Reply #21 on: May 08, 2012, 03:03:28 PM »
Because of the plateau at low ISO, I think the problem with the DR on the 5D3 comes because of the ADC

http://www.clarkvision.com/articles/digital.sensor.performance.summary/
"The dynamic range is often limited by the A/D converter and other electronics in the system, illustrated by the measured data falling below the model at lower ISOs."

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Re: How are dynamic range and sensor size related?
« Reply #21 on: May 08, 2012, 03:03:28 PM »

jrista

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Re: How are dynamic range and sensor size related?
« Reply #22 on: May 08, 2012, 03:25:43 PM »
Because of the plateau at low ISO, I think the problem with the DR on the 5D3 comes because of the ADC

http://www.clarkvision.com/articles/digital.sensor.performance.summary/
"The dynamic range is often limited by the A/D converter and other electronics in the system, illustrated by the measured data falling below the model at lower ISOs."


He explicitly called out "other electronics" as well. The A/D converter is not always an integrated part of the sensor, however the sensor contains a significant amount of complex electronic elements that can create noise on a variety of levels. An off-die ADC must usually process more pixels than say an on-die CP-ADC, so it requires a higher clock, which has a greater potential to introduce its own electronic noise into output units. Once the ADC has actually converted an electron charge into an ADU, you lose the ability to eliminate those forms of nose...they are now essentially "baked into" the output units. Sony Exmor sensors eliminate several forms of ELECTRONIC noise in the sensor before they send the charge that represents any given pixel to the ADC (which, in the case of Exmor, is also on the sensor die). Sony has two advantages...they eliminate as much electronic noise as possible before ADC, and they have one ACD per pixel column, which gives then the added advantage of eliminating vertical FPN (which is actually apparent...the D800 only seems to exhibit horizontal FPN unless it is pushed by 10 stops or more, at which point it might finally start exhibiting full cross-hatch FPN).
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Re: How are dynamic range and sensor size related?
« Reply #22 on: May 08, 2012, 03:25:43 PM »