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Getting to the bottom of the noise
  • Hi Guys.

    I've just started reviewing footage from a recent shoot and am a little perturbed by the amount of noise showing up in shadow details. The problem has occurred on a range of shots in different lighting conditions and even at very low ISOs.

    I was using a GH2 for the shoot, with LPowell's Flowmotion 2.02 hack. This was the first time I had used a Gh2 (let alone a hacked one) so it was certainly a baptism of fire. For the majority of shooting I was using a lumix 7-14 ultra-wide lens.

    I've uploaded a short clip with three different shots, each displaying the telltale noise. In the first, the noise is visible above the character's foot, on the side of the piano. This was shot at a ISO800 so it makes sense that there will be noise. Still, it seems like there is more than there should be. the second clip was shot at iso160 yet there is still a fair amount of noise showing up in the man's beanie. In the third clip, also shot at iso160, again there is a lot of noise in the man's sweatshirt.

    http://www.mediafire.com/?1m7c10p98tvy883

    I didn't fully test the patch and cam before the shoot so at the end of the day it's my problem, but I'm hoping someone can shed some light on the source of the issue so I can avoid this next time around.

    Cheers

  • 16 Replies sorted by
  • Are you aware of the bug when selecting ISO's of 160, 320 and 640? If you look in the Panasonic Camera category you will find a couple of threads

  • @Bania I have not looked at the footage but I would like to mention that the issue at ISO 800 that you mentioned would not be the result of the ISO bug, while the others might.

    The camera has some issues handling severe underexposure compared to some other models, so you might want to look to that first. A lot of people use noise reduction programs (the 3 top ones would be Neat Video, Purifier and Magic Bullet Denoiser II all of which are slightly different) and in my experience GOP1 settings have an easier time in denoising than higher GOP settings.

    If you are shooting at very high ISOs or in dark places, the current setting that achieves the best results is Canis Majoris Night (which conversely has some issues with blues if you are shooting in daytime light but is good for shade, night, artificial light and sunrise/sunset on skies without much blue).

  • Make sure you avoid the ISO bug, but the cam inherently has a bit of noise.

  • Neat Video helps alot to reduce noise just in the color channel and exposure range you have trouble with. So you can tread the noise in shadows - especially in the blue channel - without hurting important detail.

    This plugin is so amazing, it takes some time to dig in, but then its pure magic.

  • @Bania The file I downloaded from your link was not the original MTS file recorded by the GH2, so I can't really conclude anything about its encoding. It is a dark, featureless video that looks like the lens was blocked. In those conditions, the AVCHD encoder will automatically idle down to a very low bitrate which is not representative of its performance with properly exposed subject matter.

  • Thanks for the responses guys.

    While I was aware of the camera bug it is possible that for a few of the shots I may have had the camera set to iso160. Is this likely to cause the amount of noise visible in the third shot from the clip I uploaded?

    @thepalalias & Meierhans: Thanks for the tip re: neat video. Hopefully this will clean the footage up a bit.

    @LPowell. You'll have to take my word for it that the noise in these ProRes clips is more or less the same as with the original MTs files.I'm presuming you're referring to the first part of the clip when you say "dark, featureless video". I'm not sure what you mean by the lens being blocked. I was shooting in very dark conditions with a f/2.8 lens at iso800. I probably should have increased the iso but was wary of too more noise. In any case, is the lesson here that even marginally underexposed footage is prone to noise on the GH2? If I were to "properly expose" that first shot, would it not be just as noisy due to the higher iso?

    All wisdom much appreciated :)

  • P.S. LPowell: if you would like me to upload the original files I'd be happy to.

  • @Bania: man we're like brothers from another dimension or something. First shoot on GH2 on a rather involved project (10min short): check Flowmotion 2.02 untested beforehand: check Underlit night INT/EXT (DoP or lack thereof issues): check ISO800 f/2.8 (no faster wide lens available): check Well lit INT (f/4 ISO640 shutter/125) still has some noise.

    So I get craploads of noise when underexposed, AND (this seems to happen with Flowmotion only) a "snow" effect (very low frequency noise) on top of it. The "snow" happens even with substantial available light coming through a window at ISO400 f/1.8. Sorry lpowell but I will not touch Flowmotion again. I loaded stock just to have a baseline on what the cam actually does on stock firmware. There is still some "snow" but Flowmotion exacerbates it.

    Bania, the CURE is indeed NeatVideo. I have a history with the plugin, if there is one plugin I wouldn't shy away from paying again for another NLE host or OS (which somewhat outrageously they do indeed charge for) this is it. It fixes ALL kind of noise (luma/chroma), high/mid/low frequency, including the bullshit snowing which drove me mad. I ran a quick check on the raw footage and it will save my project as it always seems to do; kinda NV-man to the rescue. It may even deliver blowjobs with an advanced combination of options. It even sharpens the image and removes the flicker (I shot 23.98 with lighting on a 50Hz powergrid and there is no safe shutterspeed it seems, not 1/50, not 1/100, certainly not 1/125 I shot with).

    I'm currently testing Valkyrie 444 ZERO1 (GOP=3) for night capabilities, and I'm not impressed. I was actually looking for Canis Majoris Night, that's how I hit this thread.

  • @bania Yes, one of the lessons is to really avoid underexposing, unless you plan on crushing the shadows later or like the look of the grain for some reason. Try to keep above the middle third of the histogram whenever possible. :)

  • @bania @thepalias: My lessons for a night shoot with mainly ambiental street lighting:

    -f/1.8 or faster lens

    -Canis Majoris Night

    -Neat Video

    In that order.

  • I just made a very important test to my film, not in "low light" but in NO light. And the image is absolutely free of noise.

  • @bania I checked out the video "GH2 Flowmotion.mov" again, and found I needed to use Quicktime Player on my Win7 system to see it. It's possible that the noise may be exaggerated by the Quicktime gamma bug, so you may want to investigate that potential issue. The noise in Clip 1 is the result of underexposing the GH2. The exposure in Clip 2 is good and the noise in the shadows is typical. Clip 3 is a little overexposed, which makes the shadows somewhat milky. Of course, the contrast can easily be increased in post, which would reduce the noise visible in the shadows.

  • looks like the gh2 isn't alone in the noise department just downloaded the bmcc footage from this link and it's pretty damned noisy in the shadows too

  • @woodybrando Not really. This is a demonstration of the BMC killing every other camera under 20k. Noise is incidental compared to the DR and recorded detail being demonstrated here. Would you rather have your noise in RAW or baked into macroblocks? I'd take RAW noise personally.

    @thepalalias

    middle third of the histogram whenever possible

    Would you know what luma values this maps to? You might have seen my Avisynth script for looking at baked in noise at varying luma values. The lower the luma the coarser the noise blocking becomes until in worst cases (low datarates and encoder starvation) it posterises and macroblocks. I think this coarse artifacting is from the compression rather than the sensor but I would need low luma footage from an external recorder to confirm this once and for all.

    I am entertaining the idea of an online webapp for posting out of camera footage. The online app would transcode footage into optimal visualisation templates for comparing encoder performance as it relates to gradability and other important metrics. Was just reading about Vapoursynth which is a functional port of avisynth into Python. VS could be the building block that makes it all possible.

  • @vicx Best of luck with that. PM me if you want to make use of some of my recent SH mode testing footage (high ISO, low detail, underexposed, etc.).

  • @vicx the noise doesn't look to be a deal breaker but brought me back down to reality. no perfect cam. But I know the bmcc is young and i'm excited to see what the new firmware brings. but, no way i'm going to use a raw workflow. I've got 23 hard drives filled up and I shoot h.264 and avchd.