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Author Topic: DXO, GH2, Michael?  (Read 3080 times)
John Camp
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« on: December 02, 2010, 12:23:24 AM »
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I've very probably going to buy a GH2 as soon as they come out, and have been gathering views of the camera across the web, and those views generally seem pretty good. When you did your field report, you said you were at a loss to explain the divergence between your observations and the DXO report. I wonder if you have had any further thoughts about the matter, that might explain the differences in observation? Your opinion might be valuable to a large number of people thinking about this camera.

JC   
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michael
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« Reply #1 on: December 02, 2010, 06:00:14 AM »
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All I can say is look at the DxOMark rating for the Leica M9. It does relatively poorly, yet is almost universally regarded as one of the finest digital cameras available, challenging moderate pixel count MF cameras.

The GH2 seems to me to suffer from a similar anomalous rating. I was impressed with it back in October, and continue to be in the few days since getting mine.

I simply prefer to trust my own eyes and experience over DxOMark ratings. There is no way that a single number can summarize all aspects of image quality, let alone something as complex as a modern digital camera.

Let me put this another way. I leave in 10 days to spend the next 3 months in Mexico. I will be bringing my new GH2 and lens set as my sole camera system, since I need to travel light.

I have available a Leica M9 system, a Sony A900 / A55 system, and a Phase P65 system. So why did I choose the GH2? Not because it has the best image quality of the group. Indeed it is likely at the bottom of the list in that regard. But rather, because it is good enough, and the most versatile for the type of shooting that I expect to be doing. For me, that trumps IQ, which judged on its own merits is good enough for even exhibition quality prints up to 16X20".

Michael
« Last Edit: December 02, 2010, 07:52:22 AM by michael » Logged
billh
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« Reply #2 on: December 02, 2010, 07:23:09 AM »
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Are you escaping the Canadian winter?

The versatility is the reason I ordered a GH2. It is a small camera that offers reasonably good quality video and images, and is a heck of a lot easier to tote about than a heavy set of cameras like the EX1r and D3s, which I usually use when taking either stills or video. Hopefully you will stay in touch during your sojourn.

Have you seen the InFocus plug in from Topaz Labs? I tried it on a slightly out of focus 25mm f0.95 image and was impressed. People can get it for $29.99 using the code “Super Sharp”

For more information about the new Topaz InFocus:
   •   Visit the Topaz InFocus webpage
   •   Check out our informative InFocus Overview video.
   •   Check out our Blur Estimation video.

Have fun in Mexico (and stay safe)!
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michael
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« Reply #3 on: December 02, 2010, 07:49:34 AM »
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Escaping the Canadian winter? Now why would I want to do that?  Smiley

I have high speed internet at my house in San Miguel, and intended on being as busy as ever with the site, reviews and articles.

Safety? There were 7 shootings in Toronto last week. I'm going to SMA to escape the violence here.  Wink

Michael
« Last Edit: December 02, 2010, 07:55:53 AM by michael » Logged
Robert-Peter Westphal
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« Reply #4 on: December 03, 2010, 12:24:49 PM »
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Hi,

first I intended to buy a GH1 for my wife, she likes this camera very much because of the light weight and as stated above the versatility.
But now, after reading Michael's reports for the GH2, I changed my mind and decided to take the new GH2.

But, is the praised 14-45mm lens also a good choice for the 16MPx GH2 ?

Best wishes

Robert
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michael
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« Reply #5 on: December 03, 2010, 01:09:20 PM »
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I'd go with the 14-140mm if the extra weight and cost is do-able.

Michael
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ErikKaffehr
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« Reply #6 on: December 03, 2010, 01:55:48 PM »
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Hi,

DxO-mark is about noise and related parameters. There is more to image quality than noise.

Just to mention one parameter, a histogram that allows the photographer to correctly expose to the right can improve DR in practice.

My view in short is that the data makes sense, but the figure of merit does not.

Best regards
Erik


All I can say is look at the DxOMark rating for the Leica M9. It does relatively poorly, yet is almost universally regarded as one of the finest digital cameras available, challenging moderate pixel count MF cameras.

The GH2 seems to me to suffer from a similar anomalous rating. I was impressed with it back in October, and continue to be in the few days since getting mine.

I simply prefer to trust my own eyes and experience over DxOMark ratings. There is no way that a single number can summarize all aspects of image quality, let alone something as complex as a modern digital camera.

Let me put this another way. I leave in 10 days to spend the next 3 months in Mexico. I will be bringing my new GH2 and lens set as my sole camera system, since I need to travel light.

I have available a Leica M9 system, a Sony A900 / A55 system, and a Phase P65 system. So why did I choose the GH2? Not because it has the best image quality of the group. Indeed it is likely at the bottom of the list in that regard. But rather, because it is good enough, and the most versatile for the type of shooting that I expect to be doing. For me, that trumps IQ, which judged on its own merits is good enough for even exhibition quality prints up to 16X20".

Michael
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Ray
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« Reply #7 on: December 03, 2010, 06:03:33 PM »
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Hi,

DxO-mark is about noise and related parameters. There is more to image quality than noise.

Just to mention one parameter, a histogram that allows the photographer to correctly expose to the right can improve DR in practice.

My view in short is that the data makes sense, but the figure of merit does not.

Best regards
Erik


Exactly so, Erik. And Michael made the same point. There's no way that a single number can summarize all aspects of image quality.

A single-number rating must unavoidably be weighted or biased. However, if one takes the trouble to examine the DXO graphs, paying particular attention to the results at the normalised print size, I think one can come to some accurate conclusions about the relative image quality from different cameras at a size which is no larger than than the file size produced by the camera with the lowest pixel count. And that last point is important. Interpolating small files to match the larger file of another camera will produce different results which DXOMark do not address.

One should also be aware of the significance in practical terms of small advantages that may appear in the graphs when comparing two cameras.

For example, an increase in '1 bit' in color sensitivity is barely noticeable, according to DXO. Therfore one may deduce that any differences of 'less than 1 bit' are of no practical consequence, yet a graph that might indicate a 0.6 bit increase in color sensitivity at a particular ISO for a particular camera, might appear persuasive. All data has to be interpreted.




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ErikKaffehr
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« Reply #8 on: December 03, 2010, 11:35:44 PM »
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Ray,

Lets not kidnap this thread!

That said, what Michael says is that the DXO-Mark doesn't correspond with his experience. He finds the GH2 have at least as good image quality as the GH1.

I was looking at the DxO data for explanation and it seems that the GH2 is slightly worse in most aspects, even at print size. The reason is probably that the GH2 has more pixels, which degrades per pixel measurements a bit. DR is somewhat reduced with decreasing pixel size even when normalized to a given print size.

In my view DR is not the most important parameter regarding image quality.

Another factor is that DxO-mark is about what is coming out of the sensor or more exactly the raw file. Michael is probably interested in what is coming out of Lightroom. Lightroom has had a special treatment for Panasonic cameras a long time, as they did lens corrections for Panasonic lenses long before LR 3.0. The 14-140 zoom on the GH1 needed it! It's entirely feasible that the processing pipeline for the GH2 is further improved over the GH1.

Finally, as said before, DxO-mark is essentially about noise and tries to be an objective measurement. On the other hand, perception of noise is not objective. Some noice is more obtrusive than other. A fine but distinct noise pattern may be ok but a more grainy look may be awful.

In the black and white days many photographers used Tri-X which was quite grainy, myself always hated grain and used low ISO films like Panatomic X or T-max 100. Anyway Tri-X had probably not very god image quality but had characteristics that were liked by many.

Best regards
Erik

Exactly so, Erik. And Michael made the same point. There's no way that a single number can summarize all aspects of image quality.

A single-number rating must unavoidably be weighted or biased. However, if one takes the trouble to examine the DXO graphs, paying particular attention to the results at the normalised print size, I think one can come to some accurate conclusions about the relative image quality from different cameras at a size which is no larger than than the file size produced by the camera with the lowest pixel count. And that last point is important. Interpolating small files to match the larger file of another camera will produce different results which DXOMark do not address.

One should also be aware of the significance in practical terms of small advantages that may appear in the graphs when comparing two cameras.

For example, an increase in '1 bit' in color sensitivity is barely noticeable, according to DXO. Therfore one may deduce that any differences of 'less than 1 bit' are of no practical consequence, yet a graph that might indicate a 0.6 bit increase in color sensitivity at a particular ISO for a particular camera, might appear persuasive. All data has to be interpreted.





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Thomas Achermann
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« Reply #9 on: December 04, 2010, 01:50:21 AM »
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sorry about another kidnap of this thread  Wink
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...to spend the next 3 months in Mexico.
so can we expect to see a new tutorial where Michael and Jeff are working on their tan?  Grin
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Ray
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« Reply #10 on: December 04, 2010, 04:21:57 AM »
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Ray,

Lets not kidnap this thread!


Erik, we're bang on topic, aren't we?

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That said, what Michael says is that the DXO-Mark doesn't correspond with his experience. He finds the GH2 have at least as good image quality as the GH1.


Having just had another look at the DXOMark comparisons between these two cameras, I see that, at the same print size, with no interpolation of the GH1 file, the image quality differences are negligible in practice, according to the DXO graphs, but the GH2 has the advantage of higher resolution.

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In my view DR is not the most important parameter regarding image quality.

Who mentioned DR in this thread, Erik? Only you so far.  Grin

I would say that the DR differences between the GH1 and GH2 are again negligible at equal print sizes, although the GH1 appears to have a sweet spot at ISO 800. However, because the ISO sensitivities of these two cameras are different, it might be difficult to gauge such DR differences in practice. What would likely happen, comparing both cameras at ISO 800, is that the GH1 would require a slightly faster shutter speed for an ETTR exposure, about 1/3rd of a stop faster than the GH2. This is a very minor advantage for the GH1.

Quote
Another factor is that DxO-mark is about what is coming out of the sensor or more exactly the raw file. Michael is probably interested in what is coming out of Lightroom. Lightroom has had a special treatment for Panasonic cameras a long time, as they did lens corrections for Panasonic lenses long before LR 3.0. The 14-140 zoom on the GH1 needed it! It's entirely feasible that the processing pipeline for the GH2 is further improved over the GH1.

That's quite possible, but comparing the performance of different converters is another ball game. One can draw no conclusion about such matters from the DXO tests.

Quote
Finally, as said before, DxO-mark is essentially about noise and tries to be an objective measurement.

DXO provide measurements for SNR only at 18% grey. The other parameters are ISO sensitivity, DR, tonal range, and color sensitivity. Some cameras excel in the DR department but have worse (or no better) color sensitivity, tonal range and SNR at 18% grey. All factors should be taken into consideration, including those that DXO do not address, such as the better video performance of the GH2.

 
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On the other hand, perception of noise is not objective. Some noice is more obtrusive than other. A fine but distinct noise pattern may be ok but a more grainy look may be awful.

Noise can be reduced with programs like Topaz DeNoise, but detail that never existed cannot be created. The GH2 has a slight resolution advantage. It may well also be the case that Lightroom is better optimised for the conversion of GH2 files, but that's speculation at this stage.

Cheers!


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bjanes
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« Reply #11 on: December 04, 2010, 12:35:46 PM »
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DXO provide measurements for SNR only at 18% grey. The other parameters are ISO sensitivity, DR, tonal range, and color sensitivity. Some cameras excel in the DR department but have worse (or no better) color sensitivity, tonal range and SNR at 18% grey. All factors should be taken into consideration, including those that DXO do not address, such as the better video performance of the GH2.

Ray, that is not correct. You have to look at the full SNR graphs. They have a wealth of data if you know how to read them. Emil gives a good introduction. I think I have posted on this before.

Regards,

Bill





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Ray
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« Reply #12 on: December 04, 2010, 06:41:18 PM »
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Ray, that is not correct. You have to look at the full SNR graphs. They have a wealth of data if you know how to read them. Emil gives a good introduction. I think I have posted on this before.

Regards,

Bill

Ah! I see! You are quite right Bill. There is another heading for more detail, including the color sensitivity rating of each individual primary.

But as far as I can tell, there's no easy method of comparing different sensors when viewing the more detailed information in that lower heading.

Not being as technically minded as you, I'm more concerned with the relative performance of cameras, so the 'Compare Sensors' page, with the headings as I described, provides sufficient information to help me to make a decision. I'm not sure I need to know that the additional color sensitivity of a particular camera applies more to the blue channel than the red channel, especially if the over all differences in color sensitivity are in the order of 1 bit and less.

Most of us experienced guys know what the performance parameters are that matter the most to us. For me, the main concerns are lens quality, sensor resolution, high ISO performance, and dynamic range (within a reasonable price range that represents good value). SNR, tonal range & color sensitivity are generally so close that they are not an issue, comparing models of similar format.

I consider DXOMark a valuable tool only after one has sorted out the type of camera one would like, of the size and weight with which one is comfortable, in the price range which is acecptable, after considering the range of lenses and features one finds, or is likely to find, most useful.

Sometimes a purchasing decision can be difficult because competing camera models are often so close in performance. A slight advantage in one area is so often offset by a slight disadvantage in another area. But occasionally, a particular model of camera stands out from its competitors in one particular performance parameter that one might value.

Such was the case with Nikon D7000 for me. At its base ISO of 100, this camera has even better performance than the full frame D700 at its base ISO of 200. Not better in every parameter, of course, but at least as good in every parameter and significantly better in one parameter, namely DR which is 1 & 2/3rds EV better at equal print sizes. What a remarkable achievement!

However, at ISOs higher than 200, the D700 begins to show an advantage over the cropped-format D7000; and that's useful to know.

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