Sony EX3 Noise & Bits-Resolution & Green-Screen

It has been said ( I believe by Alister Chapman ) that there are only marginal benefits from recording XDCAM-EX to more than 8 bits, due to the relatively high noise of this camera, as compared to more typical broadcast cameras.

In my experience, while it was a wonderful step-up from my Z1, certainly it’s recordings are noisier than I’d like, leading me to pretty-process certain footage (using Neat Video denoising plugin to my NLE).  And as a recent project with reasonably well-lit green-screen illustrated, it’s noise in shadows can be a particularly nuisance (much time in post experimenting to work around this).

So I wondered:

  • Even if marginal, to what extent is 10-bit beneficial to EX3 recording?
  • For the EX3, when recording 10-bit, it is also 4:2:2, surely a benefit to chroma keying and resizing (reframing, stabilising/deshaking/tracking).
  • Could the benefit depend on editing workflow?  For example:
    • What if subsequently de-noising (like I mentioned)?
    • Some NLE’s do bits-dithering, hiding the quantisation/banding that would otherwise be apparent from having only 8 bits.

I need to do my own experiments, but for now, here (below) are some results from web-searching…


    • The camera processes the image at 4:2:2 10 bit and if you capture that image via the camera live to a suitable recording medium.device then you’ll enjoy the full glory of that imaging, but if you shot to the XDCAM EX codec and then ingested then the footage then it is very definitely 4:2:0 8 bit.
    • …the (EX3) S/N Ratio 54 dB (Y-typical) … is about 9-bit precision.
    • There is no way to really get everything from the EX3′s sensor. 
    • The Cinegammas come very close with Cinegamma 4 offering the most dynamic range. 
    • A little bit of positive black gamma may give you a touch more low end range, but your up against the cameras noise floor, so it not really going to be all that useful. 
    • Of course you really want 10 bit recording when you start to go to larger dynamic ranges to maximise your “bits per stop” but the highish noise levels mean that the amount you can grade will be limited.
    • Crispening:
      • With a high positive number the image will look cleaner and less noisy, but you will (lose) some enhancement in textures and low contrast areas as these will no longer have detail correction applied to them. This can lead to a slightly muddy or textureless look to tress, grass, skin and fabric.
      • The real problem areas are the subtle textures and low contrast areas … where the true image detail is barely above the noise level. It’s very difficult to bring these out without increasing the appearance of noise.
      • Unfortunately there is no clear answer to how to set the crispening level as it will depend on what you are shooting and how much noise you can tolerate. I tend to have crisping set between +10 and +30 for most things as I do tend to do a fair amount of grading work on my footage. When you grade noise is often the limiting factor as to how far you can push the image, so I like to keep noise under control as much as possible. For green screen and chroma key work I push crispening up to +40 to +60 as this helps me get a cleaner key, especially around subtle edges and hair.
      • If I am shooting exteriors and scenics with lots of foliage, grass etc then I will sometimes go down to -30 as this helps bring out the subtle textures in the leaves and plants, but this can make noise a little more pronounced, so it’s a trade off. And that’s what Crispening is all about, trading off subtle textures and detail against more visible noise. Ultimately only you can make the choice as to which is more important, but the Crispening level control gives you that choice.
    • (For Green-Screen work):
      • Assuming you have control over your lighting then I would use standard gamma 3 with the standard colour matrix. 
      • Shoot progressive if possible as this will have better chroma resolution 
      • and turn the detail level down to -15 to prevent hair from getting too blocky and crispening to -60 to sharpen up low contrast edges. You may want to try turning detail off all together. Some keyer’s work better with it off, some better with it on.
    • Someone with similar uncertainties to myself:
      • I just bought a nanoFlash and will use it with a greenscreen quite a bit. After some testing with my EX3 set at -3db and 280Mb I-frame, I found quite a lot of noise which makes keying with Keylight (AE CS5) a bit more difficult than I had hoped in that too much fine detail along the edges is getting cut. 
      • I find the noise creating quite a lot of varying green splotches; so, I am trying to find the best PP settings to remove the noise and make keying easier and better. 
      • So far, I have tried (lighting with) 56k as I read about there being more noise in the blue channel so 56k helps (I’m using 56k lamps in Diva 401s and Barfly 200s).
      • I am using the waveform in a Panny BT-LH1710W to get an even illumination behind a person sitting and composed from waist up. 
      • I have tried 12 various Matrix and gamma settings and they all seem very close to one another in noise levels. Everything else has been left at 0 in the PP settings.
      • I want lower noise and don’t mind loosing a bit of resolution as the video will end up as SD broadcast and SD web. 
      • Another thought is to use something like Neat Image to reduce the noise and then make the key but that will add time to the process; so, I would like to dial in the PP settings first.
    • Good, solid workhorse doc cameras. The extra depth of field makes them great for running-and-gunning.
    • I tend to use STD color matrix and Cine 4 gamma, both at level 0.
    • The internal 8-bit long-GOP XDCAM files are AWFUL for green screen. Edges are sharp, jagged blocks instead of smooth. (This is only visible when keying green screen.) Having said that…
    • This camera is GREAT for green screen if you record the HD-SDI output, which is 10-bit, with a KiPro. If you do that and record in ProRes422HQ and you’ve got yourself a very economical and very good green screen camera. The deep depth of field keeps everything sharp, which is good for compositing.
    • It’s great for white limbo as well as depth of field doesn’t matter: a sharp white background looks much the same as a soft white background.
    • I run detail at -5 to -10 overall.
    • IMPORTANT: The only kind of polarizer that can be used with this camera is a circular polarizer. The bandwidth cuts on the red, green and blue dichroic filters in the prism block are apparently so narrow that they introduce a polarizing effect, so stacking another polarizer on top of that creates some really odd color shifts. A circular polarizer polarizes light on its front surface and then depolarizes it on its back surface. The polarized “look” of the filter is maintained, but the light going through the prism blocked is not polarized.
    • IR filters: Tiffen IRNDs, Schneider Platinum IRNDs. 

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