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Dynamic range test between GH2 and 7D
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  • nomadnomad
    We all know this is quite subjective, given that the amount of noise you want to tolerate counts here.

    I did a test with the new Xyla-21 by DSC Labs (even better than Stouffer) and tested quite a few cameras under identical conditions. Judging conservatively the Alexa won with 14 stops. The 7D was 10, and the GH2 9.5 stops. If some say the Alexa has 14.5, the GH2 will have 10.
  • rozrozrozroz
    Thanks nomad.
    Good to know.
  • brianlucebrianluce
    I agree with Nomad. I've looked at DR tests and res tests. there's such a a thing as "Usable" or real DR.

  • magnificomagnifico
    @cowpunk52 is the "backlit stoufer chart" the same device with little holes giving more (twice) and more light, the same as zacuto test?

    @nomad:thx for information :-)
    How do you measure information of luminance of your chart? From a still grab of your footage do you?
    Then from a software (maybe photoshop?) you take measure of luminance from each point of light, looking for non clipped data? How?
    What I dont understand is that each spot of light is double lighted from the last. So considering the grey scale of your photo, have you got enough information do measure 14 stops!?
  • danyyyeldanyyyel
    No thay are not the same, it is more like this http://provideocoalition.com/index.php/aadams/story/canon_5d_how_much_dynamic_range_does_it_have_really/ can't find the link where someone was using one.
  • danyyyeldanyyyel
    Yes, the usable DR is another thing. Two things that chart have a lot of problem dealing with are at the highlight level channel clipping and in the shadows not only the noise level but its characteristic. Like in my test the shadow noise of the hacked gh2 is much finer and looking more like grain, that it is much more acceptable/usable to dig into them than in the Canons ones.
  • nomadnomad
    Here is the Xyla: http://dsclabs.com/Xyla

    And I check the waveform in Resolve.
  • taktak
    One thing to remember when doing thee test is how the GH2 MTS file is converted.
    It makes a huge difference.
    For example using my favourite method with 5DtoRGB you can get a lot of range using the 1.8 gamma flagging. I'm not sure it was used in the Philip Bloom shootout and that might be why the GH2 screen shot was so contrasty.
    Unfortunately 5DtoRGB has left out the 1.8 Gamma option on the new paid for "batch" app.
    They offer a way to do it using using GLSL Fragment Shaders, but I have not been ably to figure that out.
    Anyway, dont forget when comparing cameras to export the flattest image possible if you want to see the range.
  • magnificomagnifico
    @all
    I dont know how is built a grey chart for testing DR.

    From one grey to his neighbour do we double the amount of light? (1 stop difference, as we do when we are in manual mode and just divide by 2 the shutter speed)

    What is ths calculation of the RGB coordinates beetween 2 neihbours in the grey chart?
  • cbrandincbrandin
    It's not really practical to print out a DR chart. The problem is that the dynamic range printers can produce is too limited. Printers can produce a maximum density of around 2.4 - which most cameras can easily reproduce. Also, most printers produce grays by dithering - which means the grays aren't really gray. People who do DR tests procure special film plates and back-light them. Gradations and grays are surprisingly difficult to produce on charts - which is why the good ones are so expensive.
  • magnificomagnifico
    I think gamma correction affects DR of an 8 bits signal increasing it.
    I made a test with my gh2, took 2 photos :
    1/ speed 1/50
    2/ speed 1/100
    then in LR I did comparison of RGB levels on one spot in each photo.
    The ratio was 0.86 that is because of gamma correction so you can increase DR in image because of gamma.
    What about 1.8 or 2.2 gamma correction? Wich is better for DR?
  • magnificomagnifico
    @cbrandin
    I get that :-)
  • danyyyeldanyyyel
    From my test, the 1.8 gama was more just like raising the black level, than truly extending the DR, a bit what the Technicolor Cinestyle does to the Canon. It is more about perception than reality. But the reality is that there is a ton of detail in the shadows but at first sight we don't see it.
  • cowpunk52cowpunk52
    @danyyyel - this echoes my experience as well with 5DtoRGB
  • magnificomagnifico
    @danyyyel
    in a flat 8 bit image (i.e. w/ gamma) DR is 8 max :
    http://www.cambridgeincolour.com/tutorials/dynamic-range.htm
    gamma function allows the image to raise DR to 18 stops !! Because when you double luminance you don't double RGB coordinate values :-)
    My conclusion from zacuto tests and from what you are saying is that DSLR and we can say gh2 have a DR beginning in the shadows as almost the same level as top cameras (alexa, etc.) but with clipped highlight (DR =10 compared to DRs >12). The test in zacuto part 1 is done with average exposure etc.
    http://www.zacuto.com/the-great-camera-shootout-2011/episode-one
    See in video the chart at 21mn-28 s
    So if you shoot high DR image (dark parts AND lighted parts together) you will have "problems" in hight lights with gh2 because it will be clipped.
    What I want to say is that you can have a low DR camera AND good details in shadows. It depend of lot of factors, the way of binning, etc. While acquisition, you can have hardware : 14 bits processor or 10, 12 bits processor and various software dealing with it.
    High (quantity)DR doesn't mean high IQ (Quality):-)
  • nomadnomad
    Right – kind of, but what everybody is aiming for is high DR with high IQ, or it's useless…

    Plus, it's all about noise, since clipping can't be helped much. Saturation of the sensor cells is like a brick wall you're running into. Even an Alexa or a RED is saturating with hard clipping at the upper end of exposure. But reducing noise is increasing DR, since you can pull-up the shadows. Everybody is fighting for quality at the physical limits of todays sensor technology. One example: the Alexa is better in low-light, but has less resolution than the EPIC. Reason is very simple: the EPIC has more photocells on the same area (S35), so the single cell is receiving less energy.

    Compression comes into play too, since it's lumping noise information together into larger areas (and over time with GOPs), making it more obvious (and harder to cure in post). So, within the limits of 8 bit (which introduces it's own kind of noise, called quantization error) Vitaliy's hack is increasing DR of the GH2.
  • magnificomagnifico
    @nomad
    i agree: high DR, high IQ :-)

    About noise : did you see the chart :
    http://www.zacuto.com/the-great-camera-shootout-2011/episode-one
    See in video the chart at 21mn-28 s

    That means DSLR are at least on par with high end gear concerning DR on the left...
    It is a pitty since gh2 didnt do the test for shadows. But we all know that the war against noise in still photography is a huge fight. So DSLR sensors are sort of winners concerning noise (see d7000 sensor). Gh2, especially with average definition 16M sensor and a good binning for video is not so bad.

    I have seen a lot of video comparisons gh2 vs 7D, gh2 vs nex5n, nex7, 5D, 60D etc.
    Always I preferred gh2 footage. I am not a pro, it is subjective. Always I have seen crispy footage on gh2. Sort of 3D effect :-) Due to compression quality as you said :-)

    DR on the left (shadows) as you say is about noise and quality of compression for details. I think here next generation of sensors will give us some surprises. Even with small photosites ...
    DR in the right is just about A/D processor technology : just looking for more bits because highlights have so much informations.

    Give gh2, hmmm a 14bits processor for A/D conversion, give gh2 a better sensor of new generation, and you will have some gear with DR of 12-13 stops with high IQ (if highest bitrate) : just a good 2k cinema device.
  • nomadnomad
    Well, let's add one thing: 10 bits (or even 12) in recording, or you won't profit much from 12-13 stops.
  • magnificomagnifico
    :-) dreams...
  • magnificomagnifico
    I think we have to separate concepts here :
    DR is the way shadows and highlights are clipped: thats all.The tests done in zacuto test #1 show that.
    Noise/compression etc, comes in second telling the usable range plus IQ and there we have to take in account some subjective feelings.

    May be OP should change the title of post...
  • WhiteRabbitWhiteRabbit
    Zacuto's "Revenge" section (already shot?) as a follow up to their 2011 Shootout, a GH2 was said to be part of the mix of cams they wanted to be included. If GH2 shot with PTool installed and a good patch, interesting!
  • troyjasontroyjason

    As far as "useable" dynamic range goes - GH2 now tops all Canon DSLRs buy a huge margin imo (not a flame - just my opinion). I had the 7D and 5DMK2 and while people "claim" 10-11 stops - it is all mush and waxy pixels. The results are even worse when shooting at higher ISO's where things turn to soup. And don't get me started on moire and aliasing. uhhhg

    I can't prove charts and graphs to everyone here because I sold my Canon cameras - plus there is no point because the GH2 evolves every month.

    I can make my point with a video however. Download - don't stream - this guys clip shot at ISO 800 - 2000. The tones are VERY well preserved. Noise is everywhere but he didn't clean the file with his editor - it is a raw file and he was just shooting a test. Look at the extreme highlights and shadows. Remember this is after compression / export. His origial files are many gigs in size.

    He has talent and will be freaky when he gets used to his GH2's.

    The limitations of the GH2 are its 4:2:0 color space. Beyond that it handles motion, detail, usable dynamic range, and high iso far beyond what most videographers are capable of appreciating. I am not going to bash Canon DSLRs....but...

    :)

    Happy new year to everyone!

  • Ian_TIan_T

    Watched that a few times earlier. I like the noise in this. At a glance I'm subconciously thinking I'm watching actual film.

  • stipstip

    There's no way 7D or 5DmkII can be rated at 11 stops. 5D has a max of 11.5 stops - in stills mode! Only at ISO 100! How can anyone seriously measure it's or 7D's or GH2's video mode at 10-11 stops when those are the numbers they top out for stills? This is totally unscientific but I'd rate any video DSLR between 7 and 9 usuable stops in video mode.

  • troyjasontroyjason

    Stip - good point. I think Canon and their reps and fans are ridding the still image stats a bit heavy hoping nobody will notice. I made some good money with the 7D but times have changed. Loyalty to a brand for "brands sake" makes little sense these days.

    I have no fear walking onto small production sets armed with a fleet of 4 hacked GH2's, Leica, Voigtlander, and Zeiss lenses and Arri Locaster lights.

    The question is no longer Canon 7D vs Panasonic GH2 - The question is what will Panasonic bring to the table with the GH3!

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