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11-28-2013, 11:18 PM   #16
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QuoteOriginally posted by twitch Quote
Yes, no difference. Every piece of the pie is smaller (or noisier at a pixel level), but the total size of the pie is the same. Pixel size is ~3.9 microns on the K-3 so no where near the 2 microns at which point it becomes a problem..

"The[se] crops are from raw converted 16-bit TIF images converted by Canon Zoombrowser software with the same (default) settings for both cameras. Both cameras recorded the same exposure at the same ISO, and same f/ratio: ISO 400, f/4.5, 1 second exposure. The large pixels of the 1D Mark II produce higher signal-to-noise images than the small pixels of the S70. Both cameras are photon noise limited, as are these images. The signal-to-noise ratio is abut 3.6 times higher for the 1D Mark II image, equal to the ratio of the pixel pitch from each camera." R. Clark.

This difference doesn't magically disappear when pixel pitch reaches a certain size. It is less, to be sure. But the general principle remains the same. One can do all sorts of tricks in the image processor to mitigate this problem. But the physical signal to noise difference between a larger and a smaller photosite will always exist. The engineers at Pentax-Ricoh haven't changed the laws of physics.

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Last edited by Byrd-2020; 11-28-2013 at 11:21 PM. Reason: acknowledging author
11-29-2013, 01:28 AM   #17
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QuoteOriginally posted by Byrd-2020 Quote
"The[se] crops are from raw converted 16-bit TIF images converted by Canon Zoombrowser software with the same (default) settings for both cameras. Both cameras recorded the same exposure at the same ISO, and same f/ratio: ISO 400, f/4.5, 1 second exposure. The large pixels of the 1D Mark II produce higher signal-to-noise images than the small pixels of the S70. Both cameras are photon noise limited, as are these images. The signal-to-noise ratio is abut 3.6 times higher for the 1D Mark II image, equal to the ratio of the pixel pitch from each camera." R. Clark.

This difference doesn't magically disappear when pixel pitch reaches a certain size. It is less, to be sure. But the general principle remains the same. One can do all sorts of tricks in the image processor to mitigate this problem. But the physical signal to noise difference between a larger and a smaller photosite will always exist. The engineers at Pentax-Ricoh haven't changed the laws of physics.
You are comparing a full frame sensor to a tiny P&S sensor for what reason? Like I said, the size of the pie matters, not how small you slice it.
11-29-2013, 04:05 AM   #18
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QuoteOriginally posted by Byrd-2020 Quote
"The[se] crops are from raw converted 16-bit TIF images converted by Canon Zoombrowser software with the same (default) settings for both cameras. Both cameras recorded the same exposure at the same ISO, and same f/ratio: ISO 400, f/4.5, 1 second exposure. The large pixels of the 1D Mark II produce higher signal-to-noise images than the small pixels of the S70. Both cameras are photon noise limited, as are these images. The signal-to-noise ratio is abut 3.6 times higher for the 1D Mark II image, equal to the ratio of the pixel pitch from each camera." R. Clark.

This difference doesn't magically disappear when pixel pitch reaches a certain size. It is less, to be sure. But the general principle remains the same. One can do all sorts of tricks in the image processor to mitigate this problem. But the physical signal to noise difference between a larger and a smaller photosite will always exist. The engineers at Pentax-Ricoh haven't changed the laws of physics.
Try comparing a D600 and D800...
11-29-2013, 05:13 AM - 2 Likes   #19
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QuoteOriginally posted by Byrd-2020 Quote
I quote Roger Clark from Clarkvision.com: "The number of photons a digital camera collects in each pixel is directly related to the size (area that converts photons into electrons) of the pixel and the lens feeding light to those pixels. The more photons collected, the better the signal-to-noise ratio in the image, thus the larger pixel sizes using larger lenses do better in this regard. Larger pixel cameras have better signal-to-noise ratios at all levels, but this becomes more obvious especially at low signal levels compared to cameras with smaller sensors which use correspondingly smaller lenses. In the extremes of current digital cameras with small cameras having pixel sizes near 2-microns, and large pixel cameras (currently found in DSLRs), there is a factor of about 12 to 16 in photons collected. That means the large pixel camera performs at ISO 1200 to 1600 with similar noise and dynamic range performance of a small pixel camera operating at ISO 100." (part 2 of "Digital Cameras: Does Pixel Size Matter")
Clark's conclusions are contentious. I can think of 3 scientists/engineers who disagree with him. Emil Martinec's take on this topic is here:
Noise, Dynamic Range and Bit Depth in Digital SLRs -- page 3

Quoting:
Bottom line: Among the important measures of image quality are signal-to-noise ratio of the capture process, and resolution. It was shown that for fixed sensor format, the light collection efficiency per unit area is essentially independent of pixel size, over a huge range of pixel sizes from 2 microns to over 8 microns, and is therefore independent of the number of megapixels. Noise performance per unit area was seen to be only weakly dependent on pixel size. The S/N ratio per unit area is much the same over a wide range of pixel sizes. There is an advantage to big pixels in low light (high ISO) applications, where read noise is an important detractor from image quality, and big pixels currently have lower read noise than aggregations of small pixels of equal area. For low ISO applications, the situation is reversed in current implementations -- if anything, smaller pixels perform somewhat better in terms of S/N ratio (while offering more resolution). A further exploration of these issues can be found on the supplemental page. Rather than having strong dependence on the pixel size, the noise performance instead depends quite strongly on sensor size -- bigger sensors yield higher quality images, by capturing more signal (photons).
The other main measure of image quality is the resolution in line pairs/picture height; it is by definition independent of the sensor size, and depends only on the megapixel count. The more megapixels, the more resolution, up to the limits imposed by the system's optics.

Martinec's article mainly dates from 2008 and uses the 20D as the example. Since then, fill-factors have doubled and ADC noise has been reduced greatly in some brands of cameras. So his conclusion would be even more affirmed today. Check it out for yourself:

Side by side - DxOMark


Notice how the DR is similar for the D7100 (3.9Ám sensel pitch) vs the K5IIs (4.75Ám sensel pitch - both cameras are APS-C) when you look at similar sized final output sizes (the "Print" tab). If you "pixel peep" (the "Screen" tab) instead (look at individual sensel performance) you'll see a difference in DR. The reason the "Print" performance is so good these days is that the fill-factor is now very high. So the overall result is similar, because little light is being lost any more in the "cracks" between sensels.

Let's compare against some FF cameras now: K5IIs (4.75Ám, APS-C) vs D800 (4.75Ám, FF) vs D600 (5.9Ám, FF):

Side by side - DxOMark

First off, look at the SNR (18%) ("Print" tab). This is a proxy for Quantum Efficiency & Fill Factor. As you can see, both FF cameras are about 4db (1.3 stops) better than the APS-C when the overall sensor output is considered. This is due the the 2.34x larger FF sensor compared to APS-C. If we switch to the "Screen" tab, where the effect of sensel size is considered, rather than the total output performance, we see that both 4.75Ám sensels perform much the same, while the bigger 5.9Ám performs better.

Now, consider the DR. With the "Print" tab (the overall output when considered at the same display/printout size), both FF cameras are similar, with the APS-C sensor, about 0.6-0.7 stops worse. When comparing sensel performance ("Screen" tab), we again see the smaller sensels grouping together, with the bigger sensel performing better.

What about higher ISO/low light performance? I think the best indicator of this is the DxOMark Sports score. This is the highest ISO setting for a camera that allows it to achieve an SNR of 30dB while keeping a good dynamic range of at least 9 EVs and a color depth of at least 18bits. While any of the three (SNR, DR, Colour Depth) can be the criterion performance limit which is reached first and which thus determines the score, usually it's the SNR. Let's compare 3 recent high-performing MFT vs APS-C v FF cameras. I've used the K-3 as the reference:

Side by side - DxOMark

Camera Sensel Pitch ISO/Score Score Ratio Sensor Area Ratio
D800 4.7Ám 2853 2.34 2.34
K-3 3.9Ám 121611
OM-DE-M53.7Ám 8260.610.68

As you can see, the ratio of the sensor areas is a good indicator of the LL performance. It's not the sensel size that's making a significant performance difference here, since the overall sensor performance is being considered.

So, I consider it a waste of time fretting that the trend to smaller sensels is ruining sensor performance. (It's true that more sensels/mm2 increase storage & buffer size and need more processing power for the same speed.) It's better to look at the overall sensor performance, rather than looking at the size of the shrinking sensels. I see the role of more sensels per mm2 being not to enable larger printouts, but to provide more resolution (a significant factor in perceived quality), finer grained shot noise (intrinsic to light) and less visible demosaicing artifacts, at the same printout/display size.

Dan.


Last edited by dosdan; 02-05-2014 at 02:11 AM.
11-29-2013, 04:48 PM   #20
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Noise is the backgound electrical interference which become apparent when the signal level becomes weak,
The signal level is dependant on the size of the photosite combined with the efficiency of the photon collection.
Signal gains have come from multiple areas such as microlenses, less wasted space on the chip surface and more efficient photon receptors,
At the same time noise has been reduced over time in the electronic circuitry/better processing.
The K3 represents a significant improvement in noise performance to the K5 because it has nearly maintained the same signal to noise ratio as the K5 despite the smaller collection sites that result in greater resolution.
Now imagine a 16mp FF camera with the same tiny noise signal as the K3
11-30-2013, 06:05 AM   #21
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Those who believe that pixel size matters (for image quality rather than single pixel quality) are mistaken.

More pixels offset noise! - DxOMark!
11-30-2013, 03:48 PM   #22
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QuoteOriginally posted by Class A Quote
Those who believe that pixel size matters (for image quality rather than single pixel quality) are mistaken.

More pixels offset noise! - DxOMark!
Just a word for those who take DxOMark as authoritative. DxOMark's methods and results are highly contentious! So much so that they are routinely criticized by a number of user groups. (Canon groups being the most numerous.) DxOMark has, it is my understanding, only narrowly averted legal claims against them (by Leica and Canon). I do not know the precise nature of the claims against DxOMark. But there are many photographers (and engineers) who treat what they say with disdain.

Here's an image that has been circulating amongst Canon users.
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Last edited by Byrd-2020; 11-30-2013 at 03:58 PM. Reason: spelling correction
11-30-2013, 05:43 PM   #23
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QuoteOriginally posted by Byrd-2020 Quote
Just a word for those who take DxOMark as authoritative.
As falconeye writes:
"DxO tests are not w/o flaws but as of today, are still the most accurate source for the kind of properties they measure (sensor efficiency)."
The irrelevance of pixel size for image quality (which is different to pixel quality) follows from a simple logical argument. No need to believe in DxOMark procedures.

QuoteOriginally posted by Byrd-2020 Quote
DxOMark's methods and results are highly contentious!
In what way?
Can you please elaborate?

You reference unhappy user groups but user groups can be unhappy for all sorts of reasons (e.g., about the truth), so I don't find that to be a compelling argument on its own.

11-30-2013, 07:01 PM - 1 Like   #24
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QuoteOriginally posted by Byrd-2020 Quote
they are routinely criticized by a number of user groups. (Canon groups being the most numerous.)
Shooting the messenger.

If DxOMark found Canon cameras were wonderful and amazing and consistently scored their cameras better than Nikon, Canon users would no doubt be DxOMark's staunchest defenders.
11-30-2013, 07:15 PM   #25
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QuoteOriginally posted by Byrd-2020 Quote
Just a word for those who take DxOMark as authoritative. DxOMark's methods and results are highly contentious! So much so that they are routinely criticized by a number of user groups. (Canon groups being the most numerous.) DxOMark has, it is my understanding, only narrowly averted legal claims against them (by Leica and Canon). I do not know the precise nature of the claims against DxOMark. But there are many photographers (and engineers) who treat what they say with disdain.

Here's an image that has been circulating amongst Canon users.
I can understand how Canon users would not be happy with the results that DXO Mark comes up with, but they certainly are pretty consistent with real world results. DXO Mark gave the K7 a pretty lousy score when it tested it and truthfully, that was what it deserved from a sensor standpoint. I am sure that camera companies do what they can to get their sensors to score better, but there is no doubt that Canon is lagging right now from a sensor standpoint.
11-30-2013, 08:16 PM   #26
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QuoteOriginally posted by rawr Quote
Shooting the messenger.

If DxOMark found Canon cameras were wonderful and amazing and consistently scored their cameras better than Nikon, Canon users would no doubt be DxOMark's staunchest defenders.
Yes, you are probably right about this. Most Canon users who attack DxOMark likely do not understand the real issues. But can we not say the same about those Pentax users who defend DxOMark?
11-30-2013, 09:29 PM - 2 Likes   #27
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QuoteOriginally posted by Byrd-2020 Quote
Yes, you are probably right about this. Most Canon users who attack DxOMark likely do not understand the real issues. But can we not say the same about those Pentax users who defend DxOMark?
Have you read how DxOMark's data is measured?
What is DxOMark? - DxOMark

The data's primary purpose is not to say than Camera A is better than Camera B, or that Brand X is better than Brand Y. The data exists because DxO needs to carefully measure it to use it in their camera and lens correction software. The DxOMark is a secondary use of it. Because the data is measured under strict laboratory conditions, which are more tightly controlled than what is available in normal camera magazine and website testing set ups, it is a treasure trove to technically interested users. I take the composite DxOMark score with a grain of salt, but individual scores and measurements are quite useful.

Its processing by Prof Bob Newman to separate out the FWC and input-referenced total read noise has also been invaluable: Sensorgen - digital camera sensor data

Some technically-inclined users have performed their own measurements. They tend to correspond with the DxoMark data. For example:

Google Translate

Here, the Spanish telecommunications engineer (and Canon user), Guillermo Luijk, compared the SNR & DR performance of the 5DII, D700 & K5. He was very impressed with the performance achieved by the Sony IMX071 sensor in the K-5, D7000, A580 and others.

Please ensure that you move your mouse over his Fig. 3 so you can see the over-layed curve showing the improvement in S/N in the deep shadows, if a constant shutter speed and aperture are maintained, as ISO is increased. This is very interesting indeed.

With the 5DII (and other cameras with relatively high read noise), the SNR improves significantly (2.1 EV) as the ISO is raised 4 stops (ISO100 -> ISO1600).
With the D700 (and other cameras with relatively good read noise performance), the improvement is less (hence the need to raise ISO is also reduced), with SNR improving 1 EV as ISO is raised 2 stops (ISO200 -> ISO800).

The K5 (and other cameras using this Sony low read noise "wonder" sensor) have an almost flat SNR improvement curve, with SNR improving only 0.3 EV as the ISO is raised 4 stops (ISO100 -> ISO1600). Actually, since the K5 goes down to ISO80, that's 4.3 stops.

As regards DR (Fig. 5), the FF models (5DII & D700) are better at ISO800 & ISO1600. But, by ISO400 the K5 matches, and at lower ISO surpasses the FF cameras with an amazing straight-line performance to ISO80.

See also: http://translate.google.com/translate?u=http%3A%2F%2Fwww.guillermoluijk.com%2Farticle%2Fperfect%2Findex.htm&langpair=es|en&hl=EN&ie=UTF-8

Guillermo uses a different criterion to DxoMark's for his lower limit when he measures DR, so his DR figures are less than DxOmark's, but consistent. Guillermo uses a SNR of 12dB as his acceptable floor, whereas DxOMark use a floor level were the signal level = the noise level (i.e. a SNR of 0dB). So Guillermo's DR figures tend to be about 2 stops less than what DxOMark reports.
http://translate.google.com/translate?u=http%3A%2F%2Fwww.guillermoluijk.com%...hl=EN&ie=UTF-8

Choosing a DSLR is a lot more than just the imaging system. But the imaging system is the heart of it.


Dan.

Last edited by dosdan; 12-01-2013 at 04:27 AM.
12-01-2013, 02:04 AM   #28
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QuoteOriginally posted by Byrd-2020 Quote
But can we not say the same about those Pentax users who defend DxOMark?
Pentax users are all high-minded, fair and objective. A model for other brand fanboys

They don't all love and defend DxO. They can criticise DxO heartily too. Pentax users, for example, are generally are not fond of the way DxO tests Pentax lenses.
12-01-2013, 04:22 AM   #29
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QuoteOriginally posted by Byrd-2020 Quote
Yes, you are probably right about this. Most Canon users who attack DxOMark likely do not understand the real issues. But can we not say the same about those Pentax users who defend DxOMark?
Well, DXO Mark recently looked at the K3 sensor and it performed slightly worse than the D7100 sensor. And it's dynamic range at base iso was less than the K5 and K5 II. Someone started a thread afterward asking the question whether people really trust DxO Mark. The answer is that you take the good with the bad (or not so good).

I think looking at the dynamic range, SNR and sports iso gives you an idea of real world performance. Resolution is not measured by them...
02-05-2014, 01:08 AM   #30
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Is there real life difference in AF and Metering btw K3 and K5IIs?
To my specs less noise in high iso would be more value than more pixels which would make K5IIs more interesting frame. Depending on if AF and AE metering match the K3 performance.
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