Green Screen and DPX

[Mark Allen]

simple note. For Greenscreen work, just use dpx. It's a whole different world to anything else.

We're doing a challenging greenscreen project over here at Allucinari and tried a few options - avoiding dpx because of the file size. Finally we tried it (again) and realized we had wasted all the time not using it. It's not just better on a technical weird numbers level. It's quite obviously visually better.

(Evaluated using After Effects Keylight.)

(Added later for those who might not read the whole thread: tiff and dpx are of similar impressionistic quality, tiff's are larger files thus my preference to dpx. It could be proven that tiff's are technical even better, but the extra 10mb per file has to be taken into consideration for our work-flows. If someone does do tests and it seems to be much better, I'd switch to to tiff.)

[Joel Kaye]

We're doing a challenging greenscreen project over here at Allucinari and tried a few options

Thanks for the tip. It is looking like building a system capable of handling uncompressed footage may be the way to go. With hard drives so cheap now it's not that bad an option.

What other codecs did you test? Did you test Cineform? I think one of their claims to fame is it's supposed to be a good codec for compositing.

[Chris Kenny]

Of course if Red does full-quality 4K QuickTime reference movies at some point (not playable in real-time, obviously), you'll be able to feed the footage right into your compositing app at full quality without going uncompressed. Well, into compositing apps that can read QuickTime files anyway, like Shake. Pretty amazing low-budget compositing workflow there!

[Jeff Kilgroe]

I'm hoping that day comes sooner than later, Chris!

We're going to be testing this at LART. Here's a question for Mark Allen... How did EXR files hold up, assuming you tried EXR? IMO, DPX definitely seems the way to go, especially working in Shake or Nuke.

[John Tissavary]

[QUOTE=joelnet;112170]Thanks for the tip. It is looking like building a system capable of handling uncompressed footage may be the way to go. With hard drives so cheap now it's not that bad an option.

What other codecs did you test? Did you test Cineform? I think one of their

The best file format I've ever used for _ANY_ vfx work is OpenEXR.

There's none better - 16 & 32bit floating point options, flexible number of channels (I've used OpenEXR with over 60 channels, all but RGB for controlling the image in compositing). And it also supports Nvidia's Cg language so image data can be processed directly on the gpu - something Scratch & Redcine are already doing so wonderfully.

Not sure if RedCine has EXR out, but Scratch does.

cheers,

john tissavary

[Jeff Kilgroe]

Yes, REDCINE does output OpenEXR. ...Hence one of the reasons I asked Mark if they tried it. :)

I just got a R3D greenscreen clip to play with, but won't get to it until tomorrow when I have access to systems other than my G5 quad here at home.. Left my MBP at the office.

[Anders Holck]

I'm very interested in getting some r3d key footage to test.
Please send me a PM if you have something you can share.

[Mark Allen]

Yes, REDCINE does output OpenEXR. ...Hence one of the reasons I asked Mark if they tried it. :)

I just got a R3D greenscreen clip to play with, but won't get to it until tomorrow when I have access to systems other than my G5 quad here at home.. Left my MBP at the office.

Yes, we tried openEXR at my lead artists' suggestion. It didn't compare to DPX. Neither did Tiff nor (not surprisingly prores). [Again... added later and clarifying... tiff's QUALITY was the same, but the file size was so much larger, that was the comparison disadvantage of tiff.] We didn't try cineform. Is that an option? I will look into it.

I am not a scientist, so I'm totally willing to accept that my non-scientific tests were lacking. If someone would like to open my eyes to openEXR with some instructions that may clue that I did something wrong (user error), i'd be happy to try it out. 8 mb for openEXR vs. about 38mb per frame for dpx means there is an obvious advantage of openEXR.

[Mark Allen]

I'm very interested in getting some r3d key footage to test.
Please send me a PM if you have something you can share.

If there is a way of making the r3d files smaller, that would be a possibility but anyone testing would need to sign an NDA as everything I do usually is NDA for at least six months.

Is there a way to shrink down r3d?

I could maybe send out a series of frames as a few codecs as well.

[Jeff Kilgroe]

EXR in most cases is more heavily compressed than DPX, but EXR does have various incarnations and options and is intended for HDR imagery. All the info can be had at www.openexr.com . In REDCINE, the only OpenEXR parameter I recall was 16bit float color space. I need to play with the EXR output to see which version it's producing.

This is a good area for testing though -- I wonder how REDCINE goes about its EXR creation and if there are any issues in transcoding from the demosaic'd bayer wavelets to the EXR scheme and if there's any room for improvement. I'm kinda thinking that this is just a basic implementation of OpenEXR support as it only supports 16bit float (OpenEXR "half" mode). Not that support of the 32bit modes would provide any extra data, but may be useful to some for compatibility.