Thread: Compression Wedges

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  1. #31  
    What the above tells me is that REDCODE 8:1 is really the beginning of where difficult-to-remove artifacts even begin to creep in. I am reasonably confident that with a modicum of post-processing (which almost any video house would do), this can be cleaned up to a level of acceptability for nearly any client. REDCODE 10:1 make these artifacts more visible, but they remain characteristically small, and likely very easy to deal with. But, one can see even from the thumbnails that the average floor color is getting darker from 8:1 to 10:1 to 12:1, so real information is being lost. At REDCODE 14:1, the game changes, with darkening becoming more pronounced. At REDCODE 22:1, "one of these things is not like the other".

    Based on this, which is just a single image in a single studio, and using a very artificial way of looking at image noise and information, and based on setting a very picky standard, REDCODE 7:1 or better is a target if you plan no additional image processing, REDCODE 10:1 or better is fine if you don't mind doing light noise reduction in post, and that REDCODE 14:1 or more should only be used to support necessary frame rates. And I agree with Gavin that it's better to chop resolution first to meet a frame rate requirement, if the resolution is there to give.

    For a less picky standard, 8:1 or better is perfectly reasonable--it's what I use by default, and I don't bother with extra noise reduction. REDCODE 12:1 probably works fine with reasonable NR. But I think I'll stay away from higher compression rates unless necessity dictates AND testing validates the decision. YMMV.
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  2. #32  
    On today's footage we found 5k 12:1 way better than 6k 17:1. As Michael said, I see compression motion artifacts at around 10:1 on many shots. 5:1 would be my ideal although I shoot a lot at 6:1. For greenscreen work I would say it's worth going all the way to 3:1 or 2:1 since it'll save you a ton of time in keying if your channels aren't borked. I shot some 8:1 greenscreen and that ended up being a huge PITA to key since there was chroma chatter. I had to rely far more heavily on luma keys.


    The wildcard of course is how much detail there is in your scene. If your subject has lots of detail and it's surrounded by white clouds you'll be fine. The compression engine should discard all of the useless puffy white cloud detail and since they're neutral and have little to no color detail they shouldn't really artifact. Meanwhile your high detail subject will get all of the bandwidth and look great. However with the same compression option you might have a subject on a grassy field with deep focus. Now you're screwed because the compression engine will look at the image and say "Hmmm this grass is all high detail I should preserve it. But this mass of pink/brown face in the middle is really low detail. I should take some of its bandwidth and give it to the grass." So the most important part of your shot in that instance gets massive compression artifacts in order to give more data to the 'high frequency' parts of the image. That's how compression is supposed to work, but it can't distinguish between a cloud and an actor with smooth skin.
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  3. #33  
    Senior Member Nick Morrison's Avatar
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    Gavin and Michael - thanks so much!!
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  4. #34  
    Senior Member Timur Civan's Avatar
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    6:1 seems like the lowest I'd go. I ususally shoot 5:1 for safety.
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  5. #35  
    Senior Member George A.'s Avatar
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    Quote Originally Posted by Timur Civan View Post
    6:1 seems like the lowest I'd go. I ususally shoot 5:1 for safety.
    Same here.



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  6. #36  
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    It's not very encouraging for the scarlet dragon.
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  7. #37  
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    Quote Originally Posted by Gavin Greenwalt View Post
    On today's footage we found 5k 12:1 way better than 6k 17:1. As Michael said, I see compression motion artifacts at around 10:1 on many shots. 5:1 would be my ideal although I shoot a lot at 6:1. For greenscreen work I would say it's worth going all the way to 3:1 or 2:1 since it'll save you a ton of time in keying if your channels aren't borked. I shot some 8:1 greenscreen and that ended up being a huge PITA to key since there was chroma chatter. I had to rely far more heavily on luma keys.


    The wildcard of course is how much detail there is in your scene. If your subject has lots of detail and it's surrounded by white clouds you'll be fine. The compression engine should discard all of the useless puffy white cloud detail and since they're neutral and have little to no color detail they shouldn't really artifact. Meanwhile your high detail subject will get all of the bandwidth and look great. However with the same compression option you might have a subject on a grassy field with deep focus. Now you're screwed because the compression engine will look at the image and say "Hmmm this grass is all high detail I should preserve it. But this mass of pink/brown face in the middle is really low detail. I should take some of its bandwidth and give it to the grass." So the most important part of your shot in that instance gets massive compression artifacts in order to give more data to the 'high frequency' parts of the image. That's how compression is supposed to work, but it can't distinguish between a cloud and an actor with smooth skin.
    Thanks for sharing this info. Great stuff here to keep in mind.
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  8. #38  
    Senior Member Ryan Hamblin's Avatar
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    Quote Originally Posted by sam karr View Post
    It's not very encouraging for the scarlet dragon.
    That's what we kinda came to the conclusion with when we compared the scarlet x to the epic dragon. Is there a difference... Your damn right there is, but even at 6:1 on the 6k there was not a ton of detail increase... And that's looking at the footage on a 52 inch 4k display. The 6k is over all smoother at 6:1 compared to the scarlet 4k at 6:1. Detail wise you add the faintest amount of sharpening on the 4k and they feel like they resolve the same amount. You of course get to punch in on your 6k if need be, but I would reckon you will have to sharpen it if you crop much past 4k. Noise was more apparent on our tests in dragon, but more organic feeling and overall better. It's a great camera, just currently worth 20k more of my money. Scarlet dragon seems like a def no go with all the compression, but I havnt been able to test.
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  9. #39  
    Senior Member Matt Ryan's Avatar
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    Quote Originally Posted by Ryan Hamblin View Post
    That's what we kinda came to the conclusion with when we compared the scarlet x to the epic dragon. Is there a difference... Your damn right there is, but even at 6:1 on the 6k there was not a ton of detail increase... And that's looking at the footage on a 52 inch 4k display. The 6k is over all smoother at 6:1 compared to the scarlet 4k at 6:1. Detail wise you add the faintest amount of sharpening on the 4k and they feel like they resolve the same amount. You of course get to punch in on your 6k if need be, but I would reckon you will have to sharpen it if you crop much past 4k. Noise was more apparent on our tests in dragon, but more organic feeling and overall better. It's a great camera, just currently worth 20k more of my money. Scarlet dragon seems like a def no go with all the compression, but I havnt been able to test.
    In regards to noise, try the low light olpf... That will be my default olpf since I like clean images.
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  10. #40  
    Hats off, Gavin.
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