Panasonic GH2 Review for MR

[RVogie]

Michael, in your review you compare the GH2 to the Sony Nex-5.  Don't you think a more apples to apples comparison would be GH2 vs A55?

[vicfei]

Yes, I would like to know Michael's thoughts on a comparison between the GH2 and the A55 - both in terms of image quality and handling/ergonomics -

Thanks!

Vic

[Rostislav Alexandrovich]

Agreed, Sony targeted the NEX as P&S camera, and SLT A55 as for more advanced photography and is much more GH2 competitor then NEX

[elopezso]

So Michael,

Can you please comment on the question?  Many of us would like your appraisal of the GH2 versus a55?

Thx,
Ed

[Christoph C. Feldhaim]

Michael has answered this in another thread and based his answer on the lens mount.

http://www.luminous-landscape.com/forum/index.php?topic=47892.0

[BJL]

Michael has answered this in another thread and based his answer on the lens mount.
http://www.luminous-landscape.com/forum/index.php?topic=47892.0

Yes, or to put it another way: one of the dominant attractions of systems like Micro Four Thirds is the total size and weight, of a full working camera (body with lens) or of the whole kit (body, several lenses, etc.). And the only close competitors on that basis are Sony's NEX and Samsung's NX (ignoring similarly small or smaller options that are hampered by far smaller sensors or by being limited to a single focal length of a permanently attached prime lens.)

Of course, to those for whom video is a major reason for considering the GH2, comparisons to the video capabilities of alternatives like the A33/A55, D7000, 7D etc. would also be interesting; I look forward to that in full reviews of final production gear.

[Ray]

BJL,
There appears to be a lot of confusion in discussions of the GH2 regarding the 'Extra
Tele Conversion' function.

Here's all that Panasonic have to say about the feature. There's an implication that this feature might only apply to the 14-140 lens which was developed to be exclusively compatible with movie recording.

The Extra Tele Conversion function virtually extends the zoom range up to 2.6x, thus the max. 728mm* in AVCHD Cinema / FSH mode, max. 1,092mm* in AVCHD SH mode and Motion JPEG HD / WVGA mode and max.1,344mm* in Motion JPEG VGA / QVGA mode is available with the LUMIX G VARIO HD 14-140mm / F4.0-5.8 ASPH. / MEGA O.I.S. which is developed to be exclusively compatible with movie recording.
* 35mm camera equivalent.

If it works with all lenses, this would seem to be an even more extraordinary feature. The new 100-300 would then become, in 35mm terms, effectively a 200-1560mm lens, using the 'extra tele conversion' to extend the range.

As I understand, this feature is not simply a digital zoom which crops the HD movie image to a lower resolution, but a 1920x1080 pixel crop consisting of 2mp from the centre of the sensor, which would presumably have the same quality as a 1920x1080 pixel crop of a full-resolution still image done in post processing.

Do you have any information on this feature?

[BJL]

BJL,
There appears to be a lot of confusion in discussions of the GH2 regarding the 'Extra Tele Conversion' function.

Here's all that Panasonic have to say about the feature. ...

Do you have any information on this feature?

Ray, I am not an insider, but if you read on below the words you quote at the page http://panasonic.net/avc/lumix/systemcamera/gms/gh2/movie.html you will find a table illustrating the effect for both the 14-42 as well as the 14-140. Which is to say, for both of the telephoto-capable lenses sold in kits with the GH2.

So it seems mostly likely that this is purely a camera body feature, not at all dependent on which lens is attached.  As you say, it seems simply to give the option of a video image that uses all photosites within a smaller window of the sensor rather than the sub-sampling/line-dumping/binning/down-ressing or whatever that is commonly used for video output from a still/video camera. Which is roughly like having 1/2" 1080p and 1/3" 720p sensor options for any lens usable on the body.

I wonder if this enables a further electronic stabilization option for video, effectively wobbling the "read-out window" around to compensate for camera motion? That could be useful with the many lenses usable on the GH2 that are not stabilized (like my Olympus 50-200.)

[Ray]

I wonder if this enables a further electronic stabilization option for video, effectively wobbling the "read-out window" around to compensate for camera motion? That could be useful with the many lenses usable on the GH2 that are not stabilized (like my Olympus 50-200.)

BJL,
I didn't realise there was any electronic stabilisation in the GH2. If I were to buy this camera, I'd get the zoom lenses with Mega OIS. Does such image stabilisation work on a tripod? I imagine a 1500mm lens on a lightweight tripod, with even the slightest breeze, could be hopless without IS.

Do we know if there is any image quality difference between the selective 2mp across the entire sensor, as opposed to 2mp of adjacent pixels from the centre? There's ultra-confusion about this issue on dpreview.

[BJL]

I didn't realise there was any electronic stabilisation in the GH2.

Pardon my ambiguous phrasing: nor do I. I was merely speculating that this "windowed" mode could facilitate such an approach. I believe that Olympus m4/3 cameras use some kind of electronic stabilization in video mode, but do not know the details.

Do we know if there is any image quality difference between the selective 2mp across the entire sensor, as opposed to 2mp of adjacent pixels from the centre? There's ultra-confusion about this issue on dpreview.

AFAIK there has not yet been  a thorough, video-oriented review of a final production GH2 that addresses such questions, so ultra-confusion, ultra-disagreement and ultra-strong opinions based on little or no evidence is to be expected at DPReview. In a sense I hope and expect that the "windowed" mode has somewhat lower SNR and such, on the basis that if the normal mode is done well, it gets to use more than 1920x1080 total photosites and so gets to do some downsampling, and thus DR and SNR improvement. beyond what the windowed mode can. No difference would indicate that the GH2 is simply subsampling for video; something like reading only every third row and column of pixels.

[Ray]

In a sense I hope and expect that the "windowed" mode has somewhat lower SNR and such, on the basis that if the normal mode is done well, it gets to use more than 1920x1080 total photosites and so gets to do some downsampling, and thus DR and SNR improvement. beyond what the windowed mode can. No difference would indicate that the GH2 is simply subsampling for video; something like reading only every third row and column of pixels.

I suppose if I had the time I could get a good impression of the potential magnitude of the difference by taking a wide-angle shot with a zoom lens, then zooming into the same scene 2.6x taking another shot of the centre of the same scene, cropping the wide-angle shot to the same FoV as the zoomed shot, downsampling the full-frame zoomed shot to the same file size as the cropped wide-angle shot, save both as jpegs then display on my Panasonic HD plasma.

Whatever image quality differences that are noticeable would be greater than such differences should be in practice with the GH2, because we can be certain that the GH2 does not take video using all available pixels.

Another issue is of course viewing distance. When one starts being critical of image quality on a full-HD screen, one really does have to sit no further away than about 1.5x the diagonal of the screen, a distance which is much closer than the average, or generally preferred, viewing distance for most viewers of TV.

From my own experience, if I want to see image quality differences between a high quality 1080 Blu-ray movie taken with the RED video camera, and an average quality video taken at 1080i, I need to sit no further away than 2 metres from my 65" plasma screen. That's closer than I normaly care to sit.

[Rostislav Alexandrovich]

This is very puzzeling, DXO marks have tested the new GH2 and its sensor got the score of "60" vs the oldie GH1 sensor "64"
Suggesting that the new sensor has lower DR/Color fidelity and worse High ISO performance, what is going on here?
(saw first on 43rumors.com)

[Ray]

This is very puzzeling, DXO marks have tested the new GH2 and its sensor got the score of "60" vs the oldie GH1 sensor "64"
Suggesting that the new sensor has lower DR/Color fidelity and worse High ISO performance, what is going on here?
(saw first on 43rumors.com)

Wow! DXOMark was quick off the mark.

You're right. The new sensor in the GH2 does appear to be marginally worse in all respects of noise, DR, tonal range etc, but so marginally worse that I doubt in practice it means anything.

However, it's odd that Michael, in his 'first look' report on the GH2, got the impression that ISO 1600 was of more acceptable quality than the GH1. The only explanation I can think of is that ISO 1600 on the GH2 really is ISO 1600 (or 1538 to be precise), whereas ISO 1600 on the GH1 is actually ISO 2154, according to DXO. Couple that fact with the other fact that the GH2 has ISO settings up to 12,800, an apparent 2 stops higher than the GH1, it becomes easy to accept and expect that the GH2 really does have better high-ISO performance.

I think this is probably one of the traps that users of MFDB equipment sometimes fall into. They take a few shots with their new Phase back at ISO 1600 and think, 'not bad' compared to 35mm DSLRs, not realising that they are actually comparing the results from their Phase back at a real ISO of 400 with their impressions of past results from a DSLR at a real ISO of 800 to 1600.

[Rostislav Alexandrovich]

Michael, it would be interesting to hear your thoughts on this DXO conclusions, also i'm wondering if JPEG or RAW files were used in your review, i wonder if HIGH iso improvment is due to CPU processing,
Thanx for your review!

[BJL]

First, DXo does an ISO adjustment that is total garbage for th purpose at hand: it "corrects" ISO speeds on the basis of the amount of high-light head-room and then shifts SNR and DR graphs horizontally to "correct". But the compare performance at a given light level, the only normalization that should be applied is using equal shutter speed and equal f-stop to get the data used for a given ISO setting. To correct for that, the dots on the GH1 grpahs should be pushed back left to be vertically aligned with the values for the same exposure index (ISO) settings, and doing that puts the GH2 data above the GH1 data for all four measures: SNR, DR, Tonal Range, and Color Sensitivity. THe GH2 wins across the board when comparing images taken with equal exposure level (exposure time and f-stop.)

The "correct ISO" difference is simply saying that the GH2 has more high-light headroom at a given ISO setting than the GH1. And yet for improving headroom, the GH2 scores are effectively lowered. Or should I say the GH1, by having less than average highlight headroom in its A/D conversion, is perversely rewarded by having its ISO rating increased and its graphs pushed to the right.


Second, the conversion for raw measurements to the three component scores ("sports" for high ISO, etc.) and then to a single aggregate DXo score strikes me as dubious. Looking at the SNR graphs in "print" mode (which I believe is what DXo uses to compute its scores and which I agree is the best choice, being a better measure of how images will look when viewed at equal size from equal distance) there is very little difference:
http://dxomark.com/index.php/en/Camera-Sensor/Compare-sensors/(appareil1)/630|0/(appareil2)/677|0/(onglet)/0/(brand)/Panasonic/(brand2)/Panasonic
but the "high ISO scores" are differ by a substantial 20%: 772 vs 655. (And for the reasons noted above, the score should actually be higher for the GH2, not lower.)

My advice: look at the actual values at equal exposure level, probably meaning lining up the dots for a given ISO setting vertically for the cameras being compared, and pay little heed to data converted to mysterious scores on a rather arbitrary basis.

[michael]

Subjectively the GH2's IQ is far superior to that of the GH1. I am at a loss to understand DxO's numbers. They fly in the face of my own experience with these two cameras.

Michael'

[Ray]

First, DXo does an ISO adjustment that is total garbage for th purpose at hand: it "corrects" ISO speeds on the basis of the amount of high-light head-room and then shifts SNR and DR graphs horizontally to "correct".

BJL,
I can't believe you are so aggressive towards DXOMark. I hope this is not because you are a 'fanboy' of the micro-4/3rds system and cannot tolerate any criticism.

Is correcting ISO sensitivity on the basis of the amount of high-light headroom available not consistent with the principle of ETTR? If there's been one topic that has cropped up on this forum almost ad nauseum in the past, it's the principle of 'expose to the right'. If one doesn't fully utilise the highlight headroom, by using a shutter speed that is sufficiently slow, but not so slow that highlights are blown, then image quality will suffer, whether it be shadows that are slightly noisier than they otherwise would be, or mid-tones that are not quite a smooth as they otherwise would be.

But to compare performance at a given light level, the only normalization that should be applied is using equal shutter speed and equal f-stop to get the data used for a given ISO setting.

If the ISO sensitivities of two cameras are different, it's not possible to compare ETTR exposures from both cameras at equal shutter speed, equal f-stop and equal manufacturer-nominated ISOs. Either a different ISO setting has to be made to one of the cameras, or one of the cameras will over-expose or underexpose the image.

Now it's true that the DXO figures for the qualities of DR, noise at 18% grey, tonal range etc at the manufacturer-specified ISOs for these two cameras are actually better for the GH2 (with the exception of ISO 800 where DR still has the edge for the GH1).

If one were to align the red dots vertically as you suggest, according to manufacturer-specified ISO, the dots for the GH2 would mostly appear slightly above the dots for the GH1, indicating marginally better performance at the incorrect manufacturer-specified ISOs.

However, in my view, the purpose of such graphs is to describe performance at the correct ISO values, not the incorrect values. If one wishes to compare image quality at equal shutter speed and F-stop, then the GH2 should be set at a higher ISO, either 1/3rd stop or 1/2 stop higher. Alternatively the GH1 should be set at a lower ISO, either 1/3rd or 1/2 stop lower.

What the ISO increments actually are on the GH1 & GH2 is another issue. Most cameras allow ISO settings in increments of 1/3rd EV, but not all cameras allow for real 'intermediate' ISO settings. My 5D apparently allows for real ISO settings of ISO 1000 & 1250 etc, but some cameras have real ISO settings only in increments of 1 EV. The 1/3rd stop increments in between may be merely sofware extrapolations at the end of the in-camera processing chain.

If this is the case with the GH1 and GH2 models, ie. no real intermediate ISO settings, then in situations where one reduces the ISO of the GH1 to get equal ETTR shots with the GH2, at the same shutter speed and aperture, one will in effect be comparing (for example) an underexposed image at ISO 800 on the GH1, which is extrapolated in software to ETTR status simulating ISO 1250, with a correctly exposed ETTR image on the GH2 at a true ISO of 1600.

Likewise, if I'm comparing a shot taken with the GH1 at ISO 1600 with the same scene taken with the GH2 at equal shutter speed and F-stop for an ETTR exposure, I will have to increase the ISO of the GH2 to the intermediate ISO of 2000 (or perhaps higher if 1/2 stop increments are available). I will in effect be comparing a slightly underexposed image from the GH2 with a correctly exposed image from the GH1.

If the intermediate ISO settings are actually real settings derived from appropriate amounts of analog gain of the signal in the early stages of signal processing, then the line on the DXO graphs joining the dots should give one a fair indication of performance at the intermediate ISO settings.

In all situations for still images, the GH1 appears to have the image-quality edge, according to DXOMark results. But that edge appears so slight in my view, that I think for all practical purposes image quality will be about the same. If there is any noticeable difference, I would expect it to be a slight increase in resolution and detail from GH2 at large print sizes. However, the full HD video of 1080p at 24fps, and faster processing are amongst the main improvements that make the GH2 a worthwhile upgrade.

I hope all this is at least clearer than mud, although I expect for many it won't be.

I see that Michael is a bit mystified as to why the DXOMark results indicate the GH2 has no fundamental image quality improvement over the GH1.

Perhaps this could be a test case to explore the reasons for any discrepancies between rigorously tested results and visual impressions that appear to be in conflict with such results.

It might be worth noting some explanations from the DXOMark website on their results.

All Sensor Scores reflect only the RAW sensor performance of a camera body. All measurements are performed on the RAW image file BEFORE demosaicing or other processing prior to final image delivery. DxOMark does not address such other important criteria as image signal processing, mechanical robustness, ease of use, flexibility, optics quality, value for money, etc. While RAW sensor performance is critically important, it is not the only factor that should be taken into consideration when choosing a digital camera

Sensor Overall Score is logarithmic and a 5-point difference on the scale corresponds to a gain or loss of sensitivity of 1/3 of a stop.

Sensor Overall Score is normalized for a defined printing scenario—8Mpix printed on 8”x12” (20cmx30cm) at 300dpi resolution. Any other normalization, even with higher resolution, would lead to the same ranking, given that any camera that could not deliver the chosen resolution would be eliminated from the comparison.

This last point clarifies something that I was not sure about. An 8mp image seems a rather small size for normalisation of a 60mp MFDB image and a 24mp D3X image, but the message here is that the ranking would be the same for any normalised size (in respect of the P65+ and D3X) as long as it were not larger than 24mp.

[Jorginho]

Michael,

Did you do any tests with both cams in RAW? Because from what I have seen mostly, it is the JPEG that looks much better. The bandings seems othave gone at least till ISO 6400 where it is evident in some pics in the shade. I wonder what your experience was in RAW. I have read you review a week ago and I think it was mostly JPEG (?)
I liked the review very much BTW, as always.

But, I remember I have seen some RAW pictures too and they looked better to my eye also. Have you ever experienced a large discrepancy in either RAW or JPEG between your tests and DXO's tests?

I personally know that no test is 100% correct, but I find the way they test rather logical and I think DXO is highly regarded. I would not be surprised if it turns out that Panasonic has not doen a commendable job on the hardware, but they have done such a thing with their software (VEnus engine) nad thus JPEGs. Of course, if you test subjectively it is difficult to see that their ISO ratings have changed. I have alway sheld back on a more final judgment of this cam/sensor until DxO mark precisely for that reason. I tend to think that DxO just shows us what we can expect in RAW.

In the end, ISO and DR are important but the improvements in the GH2 are clear in other areas. Like the EVF, like the AF and moviemode. More MXPixel allows for better copping and more detail. As mentioned, the banding is gone. And if you like it: the well thought out touchscreen. A good JPEG engine by Panasonic with better colours was badly needed. At least many felt it was subpar. So the Gh2 as a camera seems much better than the GH1 even in the IQ department if you ask me. A slightly worse ISO performance is just a part of total IQ. The disappointment I have seen on many fora discussing this cam can be explained by high expectations. First because it is a new sensor, so you do expect it automatically. Second, because APS sensors by Sony have become much much better in the last generation in the DR and ISO department (look at the K-5). And of course the reviews we have seen by some people, showing us what we hoped for.

[michael]

All my shooting was done in raw.

I did no direct comparisons with the GH1 or any other camera, not any rigorous testing for IQ. The camera I used was preproduction and there's not much point in doing IQ tests until V1 of the software is ready, which I understand it now is.

I expect to do some serious shooting and testing with the GH2 once the one that I have on order arrives, hopefully toward the end of this month.

Michael

Ps: But, I did enough shooting with the GH2 and made enough prints to know where its IQ fits into the scheme of things, and what I see has it a visible notch above the GH1 and in the same ballpark as the NEX 5.

Michael

[Rostislav Alexandrovich]

Michael, I am eagerly waiting for review of the final production GH2, i would like to ask one thing if its possible, i see it as the most important (in the HIGH iso debate anyway)

Could you please make direct high ISO comparison with GH1 using the same Aperture&Shutter speed (leaving the ISO on auto) because there are strong evidence that GH1 and GH2's ISO values Do Not Match!

Thanx again! waiting for your further analysis