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GH2 ISO noise bug at 320, 640, and 1250
  • The GH2 ISO bug for 320 has been documented already: if you switch from ISO 250 to ISO 320, there's more noise than if you switch from ISO 400 to ISO 320. I have mapped the bug for ISO 640 and ISO 1250 as well. It seems that the bug is exhibited regardless of whether you record or not.

    Switching to ISO 320: low noise from 400, 500, or sometimes 640; high noise from all others and from power off
    Switching to ISO 640: low noise from 800, 1000, or 1250; high noise from all others and from power off
    Switching to ISO 1250: low noise from 1600 or 2000; high noise from all others and from power off

    I couldn't detect the bug when switching to any of the other ISO settings - if it's there, it's subtle. But for 320, 640, and 1250, it was unmistakable. Aside from the bug, I would say that none of the ISO levels seemed particularly more or less noisy than would be expected. I'd say to use whatever ISO level you need, being careful to avoid the bug.

    Note that it is not sufficient to simply switch from any higher ISO to avoid the bug.

    A good practice for ISO 320, 640, and 1250 would be to switch to the ISO setting 1/3 stop higher, and then back down. (i.e., 400 to 320, or 800 to 640, or 1600 to 1250).
  • 62 Replies sorted by
  • yea, I just noticed this a week ago... super weird. I wonder what's going in that camera to cause this... ???

    Thanks for the tip on 640 and 1250... ;)
  • It is just too smart, and some switches result in simple RAW processing.
  • Just to be sure, would it be safe to switch to ISO levels through ISO 160?
  • omg, panny HAS to fix this. i had the high noise on a night shoot on 320. it ruined my shot...
  • @balazer and everyone...
    Does cycling the power fix this issue? (As in set to an iso- then cycle- no noise?)

    Cheers,
    Alex
  • I don't believe cycling helps. No, each user seriously needs a sticky on the camera with the reminder to got from high ISO to low. You know how it gets when you're running and gunning... I haven't noticed this at 640/1250 (we rarely shoot high ISO), but at 320, indeed, it's a shot wrecker... has happened to us too.
  • I just tested power cycling: powering the camera on in 320, 640, or 1250 ISO causes the bug, regardless of what ISO setting you had previously.

    For anyone interested in testing this himself or herself, it's pretty easy: turn on ETC and 4x zoom, defocus the lens, and adjust the exposure until you see lots of noise on the LCD. Then start switching between different ISO settings. You can use the touchscreen to switch between any two ISO settings.

    And do note that the bug happens when switching from 2500 to 1250. So it's not sufficient to simply switch from higher to lower by adjacency in the on-screen ISO menu. A correct rule would be to switch from the next highest increment by number, e.g. 1600 to 1250.
  • My simple fix has been to bake in 1600 as the default ISO for my C1/C2/C3 modes, so when I turn the camera on or switch to a different mode I'm forced to turn ISO down. Takes one more thing off the to-do list.
  • That is a very clever workaround to the issue. Good idea.
  • Vitaliy, are you suggesting that this bug is simply disabling some NR rather than misconfiguring the sensor? I'm not convinced either way. If that were the case, then this would actually be desirable behavior for those who prefer to have the camera do as little NR as possible, and then do NR after the fact in software.

    To my eyes, at least, I see no evidence of excessive NR at -2.
  • @balazer "Simple raw processing" can mean anything. I would say that considering the bug - somehow the correct mode is not 'locking in' - could even be lower bit rate from the original 12bit samples...

    Suffice to say that @VK is probably the only one who knows the code enough to work this one out...
  • I think it is not the bug, just camera wants to reduce number of actual amplifier changes.
    So, it depends on direction of ISO increase and your current ISO.
    If it thinks that it can make things work without actual amplification change, just by shifting RAW, it is doing so.
    This is my understanding of this behaviour.
  • Considering what VK has mentioned above- then possibly this issue could be dependent on the current illumination- (the cam sensors a certain light- then trys to do the best it can- regardless of ISO setting)
  • Same settings, same conditions, different results depending on which setting you had previously: that's a bug, or oversight, or incorrect assumption, or just lazy programming. VK knows much, sure, but do not forget about Panasonic engineers. They know a thing or two also. ;)

    Anyway we don't need to get into a debate about whether it's a bug or what is causing it. The important thing is it's real, repeatable, and observable, and with the proper knowledge, avoidable. And I do hope it will be fixed, because in the flurry of shooting it is very easy to forget about this problem!
  • For me the only workaround for shoot an run, is not to use any of the 320 640 1250 iso settings. And if its time enough, as Shaveblog said, 1600 as a default.

    I understand Vitaly a bit like driving a car. If i came down from 100km/h, i will often drive in fourth gear at 50km/h. And when is speed up, i will stay quite longer in third gear for the same speed. Of cause third gear will take more fuel, but the result 50Km/h is the same. Even if it is a bit noisier. Simplified: More noise at the same speed depending where you came from ;-)
  • @Gerald Good analogy. And dammit, I used the GH2 to get a safety shot of a concert and got it all home and saw the video was a bit noisy. And then I realised I'd done exactly that - gone from 160 to 320 and left it at 320. If the LCD had peaking I'd have spotted the noise. Damn again!!
  • Sorry for re-up this old (but useful!) thread but i haven't found an information:
    Do you think Auto-ISO have the ISO problem?
  • Wonder if this holds true for the new firmware. Doesn't look like there's an workaround other than remembering the combinations that produce lower noise.
  • From what I red it was not fixed.
  • Auto ISO mode is a bit different from manual ISOs in that it has sub-1/3 stop increments, which give smooth variation in brightness. For this reason, it's hard to detect the bug in auto ISO mode, and I haven't tried. My guess is that auto ISO mode has the bug just like in manual ISO mode, with noise decreasing as you move away from ISO 320, 640, and 1250.

    My personal view is that if you want to use auto ISO, go ahead and use it and don't worry about the bug. It will be good enough, for the kind of shooting that auto ISO is helpful for. I've used auto ISO on occasion, and it always looked fine.
  • Hi balazer and thank for reply.
    Yes it's really hard to notice the bug but guess that is present too, because we can't don't lock the auto-iso when we are in Shutter priority mode (AE-lock fix auto-iso too).
  • I've spent nearly twenty years in photography and I'm brand spanking new to this GH2. I'm reading up on everything I can find before it arrives -- and this issue above scares me.

    Please help me, as I'm the "newbie" and/or "idiot" type.

    From reading the above -- will the following rule ALWAYS resolve this issue?......

    -- Find whatever ISO I want to use, switch to one setting higher, and then back to one setting lower --

    Will that always resolve this issue?

    My thanks and best regards.
  • Does one have to actually select the higher ISO and close the ISO menu, then press the ISO button again and select the lower ISO, or is it sufficient to simply move the cursor down to the next ISO and back when making the selection?