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Author Topic: DXOmark ranks DB image quality well below DSLR!  (Read 33584 times)
photolinia
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« on: April 25, 2009, 01:13:55 AM »
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Reading through a photo magazine I saw an ad for DXO mark - http://www.dxomark.com/ -
a company that claims to test raw image quality of most cameras and backs based on
color deapth, dynamic range, and low light ISO.

Looking through their database, they rate D3X the highest, and it was quite shocking to see H3DII-39 and P45+ come in well behind
many prosumer grade DSLR's...  
I did not expect medium format to do well in low light ISO, but they rank behind many DSLR's even in color deapth and dynamic range...
Is there any sense in what these guys are doing?  I'm curious if anyone is familiar with their test methods.

thanks!
-ilya
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Nick_T
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« Reply #1 on: April 25, 2009, 01:39:19 AM »
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Quote from: photolinia
Reading through a photo magazine I saw an ad for DXO mark - http://www.dxomark.com/ -
a company that claims to test raw image quality of most cameras and backs based on
color deapth, dynamic range, and low light ISO.

Looking through their database, they rate D3X the highest, and it was quite shocking to see H3DII-39 and P45+ come in well behind
many prosumer grade DSLR's...  
I did not expect medium format to do well in low light ISO, but they rank behind many DSLR's even in color deapth and dynamic range...
Is there any sense in what these guys are doing?  I'm curious if anyone is familiar with their test methods.

thanks!
-ilya
This was discussed maybe a month ago.. I think DXO have their own agenda, I have (and love) a D3 as well as an H3D31 (love it too), each have their place just as the equivalents did in the film days. I'm no scientist and frankly cannot be bothered to examine the science behind DxO's claims.
 I do know for a fact that certain gear works better than other gear for certain jobs..
Nick-T
« Last Edit: April 25, 2009, 01:43:03 AM by Nick_T » Logged

photolinia
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« Reply #2 on: April 25, 2009, 01:44:47 AM »
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Quote from: Nick_T
This was discussed maybe a month ago.. I think DXO have their own agenda, I have and love a D3 as well as an H3D31 each have their place just as the equivalents did in the film days. I'm no scientist and frankly cannot be bothered to examine the science behind DxO's claims. I do know for a fact that certain gear works better than other gear for certain jobs..
Nick-T


I agree with you, and I missed the original discussion...  from personal experience, I know that D3 is a LOT better at low light and fast action photography than an H3D-39, but when it comes to image quality, D3 can not really compare.  That's why it seems so shocking that DXO found D3 to produce better
image quality...

oh well - I was only curious.
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elf
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« Reply #3 on: April 25, 2009, 03:08:22 AM »
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Quote from: photolinia
I agree with you, and I missed the original discussion...  from personal experience, I know that D3 is a LOT better at low light and fast action photography than an H3D-39, but when it comes to image quality, D3 can not really compare.  That's why it seems so shocking that DXO found D3 to produce better
image quality...

oh well - I was only curious.

If I were buying a camera today, I certainly wouldn't base my decision on Dxo (or even consider using Dxo in the decision process).
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rethmeier
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« Reply #4 on: April 25, 2009, 03:15:31 AM »
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Well,
I'm getting better results in the shadows(less noise) with my D3x,compared with my Hy6/75LV.
I certainly don't believe that a MFDB has more DR than my D3x.
Also,I sold my MFDB kit,so I don't really care anyway.
I don't make big prints and I'm not a landscape shooter.
All I want is an easy camera to work with.
Best,
Willem.
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Willem Rethmeier
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ErikKaffehr
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« Reply #5 on: April 25, 2009, 10:03:19 AM »
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Hi,

DxO essentially looks at noise related parameters and also low light ISO. They put no weight on resolution just take it into account regarding noise measurements. The measurements are probably correct. Their only agenda is probably to sell their DxO product, which is probably quite good as Alan Briot obviously likes it.

One area that may be of significance here is that MFDB use sensors from Kodak and Dalsa which need more calibration data than the Canon and Sony sensors employed by most of the DSLRs. According to PhaseOne each "raw" image from a Phase One DB contains something like one Megabyte of proprietary info about the individual sensor chip. This info can be utilized by the PhaseOne software but probably not by DxO.

The fact that MFDBs do not perform well at high ISO indicates that they have some form of weakness regarding noise. I never did fully understand this, if DR is high it should be possible to utilize it as a high ISO.

It's quite obvious that people who own but MFDBs and DSLRs seem to agree that the MFDBs deliver better image quality, but it's probably not in the area that DxO measures. For instance there is some discussion of "microcontrast" a term that is not very well defined but seems to be related to MTF for fine details and this may also relate to quaility of optics and presence/absence of optical low pass filter (AA-filter). Without the AA-filter thee image will have higher MTF but also contain false detail which may improve perception of sharpness but still is an artifact.

Best regards
Erik

Quote from: photolinia
Reading through a photo magazine I saw an ad for DXO mark - http://www.dxomark.com/ -
a company that claims to test raw image quality of most cameras and backs based on
color deapth, dynamic range, and low light ISO.

Looking through their database, they rate D3X the highest, and it was quite shocking to see H3DII-39 and P45+ come in well behind
many prosumer grade DSLR's...  
I did not expect medium format to do well in low light ISO, but they rank behind many DSLR's even in color deapth and dynamic range...
Is there any sense in what these guys are doing?  I'm curious if anyone is familiar with their test methods.

thanks!
-ilya
« Last Edit: April 25, 2009, 10:03:47 AM by ErikKaffehr » Logged

jimgolden
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« Reply #6 on: April 25, 2009, 12:46:20 PM »
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we've been down this road...keep dreaming...
« Last Edit: April 25, 2009, 12:47:36 PM by jimgolden » Logged
Graham Mitchell
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« Reply #7 on: April 25, 2009, 01:08:48 PM »
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Quote from: ErikKaffehr
They put no weight on resolution just take it into account regarding noise measurements.

It seems to be a very common mistake to disregard resolution when comparing noise samples. People tend to view both images at 100% to look at the noise, which is understandable, but they forget that each pixel of noise on a 39MP camera is only going to be one quarter the area on the final print compared to a pixel of noise from a 10 MP camera. Big difference, and this means that on a per-pixel basis, the 39MP camera can afford to be a lot more noisy. It also means that noise reduction can be applied more aggressively and you will still be left with more detail.
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photolinia
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« Reply #8 on: April 25, 2009, 01:30:27 PM »
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Quote from: foto-z
It seems to be a very common mistake to disregard resolution when comparing noise samples. People tend to view both images at 100% to look at the noise, which is understandable, but they forget that each pixel of noise on a 39MP camera is only going to be one quarter the area on the final print compared to a pixel of noise from a 10 MP camera. Big difference, and this means that on a per-pixel basis, the 39MP camera can afford to be a lot more noisy. It also means that noise reduction can be applied more aggressively and you will still be left with more detail.
I thought that too, but then d3x came in ahead of d3. How can that be?
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yaya
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« Reply #9 on: April 25, 2009, 01:56:35 PM »
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Quote from: photolinia
I thought that too, but then d3x came in ahead of d3. How can that be?

Sony sensor and a newer processor
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ErikKaffehr
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« Reply #10 on: April 25, 2009, 02:11:21 PM »
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Hi,

They actually take resolution into account by normalizing to 8 MPixel size. Problem is that most of us regard a high resolution picture to be better than a low resolution one if the noise level is the same. I guess that very few would spend more than 2000 USD on any camera (except a golden Leica) if they would not print larger than 8x10". Cooking everything into a single figure of merit is more that dubious IMHO.

The DxO-site has good information on this: http://www.dxomark.com/index.php/eng/Insig...s-offsets-noise!

Best regards
Erik

Quote from: foto-z
It seems to be a very common mistake to disregard resolution when comparing noise samples. People tend to view both images at 100% to look at the noise, which is understandable, but they forget that each pixel of noise on a 39MP camera is only going to be one quarter the area on the final print compared to a pixel of noise from a 10 MP camera. Big difference, and this means that on a per-pixel basis, the 39MP camera can afford to be a lot more noisy. It also means that noise reduction can be applied more aggressively and you will still be left with more detail.
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ErikKaffehr
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« Reply #11 on: April 25, 2009, 02:20:36 PM »
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Hi,

There are a couple of questions about the Nikon 3Dx. It has a 14 bit capture mode which is much slower than 12-bit mode. It is not very clear how this is achieved, as it seems that it uses on chip converters whether 12 bits or 14 bits are used as ADC components seem to absent from the circuit boards in the camera.

Best regards
Erik


Quote from: yaya
Sony sensor and a newer processor
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Guillermo Luijk
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« Reply #12 on: April 25, 2009, 02:21:52 PM »
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Quote from: foto-z
It seems to be a very common mistake to disregard resolution when comparing noise samples. People tend to view both images at 100% to look at the noise, which is understandable, but they forget that each pixel of noise on a 39MP camera is only going to be one quarter the area on the final print compared to a pixel of noise from a 10 MP camera. Big difference, and this means that on a per-pixel basis, the 39MP camera can afford to be a lot more noisy. It also means that noise reduction can be applied more aggressively and you will still be left with more detail.
DxOMark put the different resolution into the equation with the 'Print' option in the DR and SNR18% tests:
- SNR18% represents well the amount of noise in correctly exposed areas of the RAW file. Both Nikon D3X and H3DII 39 perform the same here.
- DR represents well the amount of noise in the deep shadows of the RAW file. The Nikon D3X is a clear winner over H3DII 39 here.


I was a bit surprised when I saw the ISO plot for the back:



My interpretation is that the H3DII 39 has just one real ISO: ISO50. All over values are fake ISOs obtained from ISO50.

BR
« Last Edit: April 25, 2009, 02:23:24 PM by GLuijk » Logged

Graham Mitchell
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« Reply #13 on: April 25, 2009, 02:25:32 PM »
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Quote from: GLuijk
My interpretation is that the H3DII 39 has just one real ISO: ISO50. All over values are fake ISOs obtained from ISO50.

I think that's true for all MFDBs
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Guillermo Luijk
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« Reply #14 on: April 25, 2009, 03:16:14 PM »
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Quote from: foto-z
I think that's true for all MFDBs
It seems the Phase One has ISO50 and 100, and the Leaf ISO50, 100, 200, 400 and 800. Only the Hasselblad has a unique real ISO, of 50.
Probably this does not mean anything, just that users should avoid fake ISOs if there is a risk of losing highlights information.

« Last Edit: April 25, 2009, 03:18:06 PM by GLuijk » Logged

BernardLanguillier
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« Reply #15 on: April 25, 2009, 03:45:05 PM »
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Quote from: foto-z
It seems to be a very common mistake to disregard resolution when comparing noise samples. People tend to view both images at 100% to look at the noise, which is understandable, but they forget that each pixel of noise on a 39MP camera is only going to be one quarter the area on the final print compared to a pixel of noise from a 10 MP camera. Big difference, and this means that on a per-pixel basis, the 39MP camera can afford to be a lot more noisy. It also means that noise reduction can be applied more aggressively and you will still be left with more detail.

True, on the other hand if you do the same computation between a 39MP back and a D3x, you will realize that a the same DPI, the linear size of the print you can achieve is only 1.25 times larger, meaning that you can go from an A4 print (29.7 cm long) to one that is 37cm long.

It can of course be argued that the 39MP AAfilter less back has higher pixel quality, which is true to some extend.

Now, these 39MP back are old technology, and it would be interesting to see what companies like Kodak and Dalsa could do with 39MP if they tried today, but it seems that they have been stucked in the MP race like everybody else and will not develop any new sensor with that kind of resolution.

Cheers,
Bernard
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A few images online here!
photolinia
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« Reply #16 on: April 25, 2009, 04:38:11 PM »
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Quote from: foto-z
I think that's true for all MFDBs

Hmmm...  Could somebody explain this real ISO vs fake ISO issue?
I thought that all cameras had one base ISO  (50 for most MFDB, 100 for D3X, 200 for D3), but then
used amps to simulate the effect of higher ISOs - is that not the case?

what is the difference between the way D3X and H3D-39 derive higher ISO's?

-ilya
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Guillermo Luijk
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« Reply #17 on: April 25, 2009, 05:28:39 PM »
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Quote from: photolinia
what is the difference between the way D3X and H3D-39 derive higher ISO's?
Real ISOs refer to the gain of the amplifier that feeds the captured information from the sensor into the AD converter.
Fake ISOs are shots obtained at a different (usually lower) real ISO value and then overexposed by the camera software.

A camera usually has some real ISOs, and also several fake ISOs. For example on a Canon 5D, ISO3200 is fake ISO. The shot is actually taken at ISO1600 and then overexposed by 1 stop (all levels are multiplied by 2) before saving the RAW data.

A fake ISO like the ISO3200 on the Canon 5D has no noise advantage when shooting RAW over shooting at the same aperture/shutter using the lower real ISO (ISO1600 in the example), because it's actually a ISO1600 shot. But the fake ISO can make us loose up to 1 stop of highlights information because of the overexposure.
So fake ISOs should always be avoided when shooting in RAW mode or we can loose DR in the highlights when comparing to shooting at the same aperture/shutter with the highest real ISO.

In JPEG mode all ISOs are fine, as long they help us to achieve the correct exposure in the final image, since this will be hardly corrected.

Looking at the plot, it seems the Hasselblad has only one real ISO (ISO50). When setting ISO100, 200 or 400 on that camera, the shot will be internally done at ISO50 and then respectively overexposed by 1, 2 or 3 stops in software. So shotting at any ISO over 50 in the Hassy is useless and can make the user loose highlights information with respect to using the same aperture/shutter and ISO50.

BR
« Last Edit: April 25, 2009, 05:33:30 PM by GLuijk » Logged

Panopeeper
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« Reply #18 on: April 25, 2009, 08:00:56 PM »
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Quote from: foto-z
I think that's true for all MFDBs
This is not so straightforward. I can make definitive statements only relating to a few models and a few ISO steps:

Phase One P25 Plus: no difference from 100 to 800, i.e. fake latest from ISO 200

Phase One P30 Plus: real up to 200; 400, 800 and 1600 are fake

Phase One P45 Plus: real at least up to 800

Sinar e54: already ISO 100 is fake

Hasselblade announced a short while ago ISO 1600 for whatever back. They (the users on this forum at least) have not noticed, that this happens without any hardware upgrading. I saw only a small side-note stating, that the ISO increase is due to the better noise reduction of the raw processor. I would have loved to have such  digitally challenged customers as Hasselblade's are.

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Gabor
photolinia
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« Reply #19 on: April 25, 2009, 08:09:16 PM »
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Quote from: GLuijk
Real ISOs refer to the gain of the amplifier that feeds the captured information from the sensor into the AD converter.
Fake ISOs are shots obtained at a different (usually lower) real ISO value and then overexposed by the camera software.

A camera usually has some real ISOs, and also several fake ISOs. For example on a Canon 5D, ISO3200 is fake ISO. The shot is actually taken at ISO1600 and then overexposed by 1 stop (all levels are multiplied by 2) before saving the RAW data.

A fake ISO like the ISO3200 on the Canon 5D has no noise advantage when shooting RAW over shooting at the same aperture/shutter using the lower real ISO (ISO1600 in the example), because it's actually a ISO1600 shot. But the fake ISO can make us loose up to 1 stop of highlights information because of the overexposure.
So fake ISOs should always be avoided when shooting in RAW mode or we can loose DR in the highlights when comparing to shooting at the same aperture/shutter with the highest real ISO.

In JPEG mode all ISOs are fine, as long they help us to achieve the correct exposure in the final image, since this will be hardly corrected.

Looking at the plot, it seems the Hasselblad has only one real ISO (ISO50). When setting ISO100, 200 or 400 on that camera, the shot will be internally done at ISO50 and then respectively overexposed by 1, 2 or 3 stops in software. So shotting at any ISO over 50 in the Hassy is useless and can make the user loose highlights information with respect to using the same aperture/shutter and ISO50.

BR

Oh - very interesting - thanks!

So, does that mean that in Nikons all the"Hi" and "Low" settings are the fake software ISO's and the ones designated with actual numbers are real internal amp setting ISO's?

-ilya
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