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Thread: Picture Noise

  1. #1
    Join Date
    Jul 2007
    Hertfordshire, UK

    Smile Picture Noise

    Hi guys,

    I'm stumbling on a problem as I rough edit some new footage. The footage itself is quite overexposed, and that's all well and good. But when I look at the screen at an angle, I see a lot of digital noise happening amongst the whites, and darkening the picture makes the noise very easy to see.

    The footage was shot in 720p HD on a Panasonic AG-HPX171, using P2 cards. The footage was then exported from Final Cut Pro into Apple Intermediate Codec for me to use at home on my Final Cut Express.

    I've come across this type of noise before on still images, but never really known what it is or what is is causing it. Could anyone help me understand what exactly is going on with this picture, and if there is, any way of fixing it or making it a little better?

    Here's a still from a lightly colour corrected part in the footage:

    Here's the same still darkened in Photoshop to show you what I see (the lines on the left):

    Is it compression? The whites being too overexposed? The limitations of the monitor? :/
    Last edited by BritishEye; 04-19-2011 at 01:27 PM.

  2. #2


    If I'm right, the Panasonic AG-HPX171 shoots in DVC Pro HD format which is 10 bit 4:4:2 (which basically means a lot of colour info) if it has been rendered at a lower bit rate the software will do it's best to put in a pixel colour as close as it can. This isn't always perfect so you can get noise like your example.

    The above makes me sound as if I have a clue as to what I'm talking about but I don't really.

    This problem could just be a bad filming job, ie if they didn't have enough light so they turned up the gain that would cause graining or it could just be a rendering issue, I don't really know without seeing the original footage. It is a nightmare to get rid of if possible and usually never with fully satisfactory results. I would normally try increasing the contrast is the exposure wasn't so high already ie killing some of the dark areas can hide the noise or burn out the white noise but all it is doing is hiding it. Something like a soft blur might help.

    Good luck.

  3. #3


    I've been trying to improve my colour work knowlege recently and was reading that often noise falls only, or at least mostly, in a single channel. You can inspect the individual channels in after effects, or even photoshop. It said that sometimes as a quick fix you can get good results replacing the noisy channel with a duplicate of one of the clean channels.

    It definately said that one of the channel mixer/combiner/shift tools in After Effects can do this, but I can't remebr which and I just had a quick dabble and can't get the desired results. If I get a chance to look back for it I'll reply here. If not, and if you find out, I'd apreciate if you did too.

    Other than that, depending on what tools you are using, you could minimise the adjustments you are making in the areas that have most problems. Looks like the highlights. You can create mattes from channel information to do this but there's a lot of different vocabularies in relation to a lot of different software/hardware and it's really not my strong point to feel overly comfortable with trying to offer much in the way of information on it. If you look up "secondary colour correction techniques" I can imagine you'll find something.


  4. #4


    This'll be a quick one, I'm just heading out for the day. I had a quick look last night and right enough it's the chanel mixer in sfter effects, it allows you to reduce the amount of the noisy channel while mixing it with the clean channels.

    This is how I remembered it, but wasn't getting any results. The missing link is that ythis step is just to clean up the problems. Then you need to do further colour adjustments to bring the picture back to normal colours. To do this I can imagine you'd need to monitor with the RGB parade.


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