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Thursday, March 19, 2009
5 Tips to Maintain Sanity in RED Post
Mark Christiansen | 03/19
Lose less life working with R3D source
Tip 4: Take control of sharpness, noise and more at the time of conversion
Once again, this may be fodder for another article another time, but RED output will look a little soft at 4K not because the camera doesn’t truly deliver 4K - it does (although careful tests show it resolves somewhere closer to 3K) - but because the camera performs no sharpening. Those of you who have worked with video cameras for the last couple of decades may find this to be a shock, but rather than being something you must try to eliminate, sharpness is something you must in fact add to R3D output.
Use the Debayer Detail setting in REDAlert (as well as the RED settings in After Effects and Premiere) - set it to High and you have at least introduced a modest amount of sharpness, but be prepared to add more as needed. The problem is rarely too much.
Similarly, although RED footage is already way lower on noise than pretty much any film footage and most video footage you might have used, you have control over the amount of Chroma Denoise and OLPF Compensation. OLPF stands for Optical Low Pass Filter; its target purpose is the elimination of moire fringing, but you may find it pleasingly de-noises your image overall. The amount of Chroma Denoise required may be none, or you may find that one of the 6 levels of denoise to the red and blue channels helps your shot.
The simple act of down-sampling resolution can and will make your RED source look sharper at 720p or D1.
Tip 5: Make use of great free and cheap tools to help your workflow
If you’re on a Mac, there are several tools available for free or cheap to help you complete the RED workflow. I’ll focus on a couple of them here, and save a more complete rundown for another time.
REDAlert is the most useful RED-related tool you can download for free. It is essential that you get at least this software for two reasons: first, it is the best place to do basic adjustments to an R3D file, and second, it includes Redline, the command line utility used by many other free and shareware apps to work with those files. In a future article I share more about how to use REDAlert to understand the R3D file, but it’s one place you can create your main color settings, making certain that your highlights are balanced and not clipped using the Histogram along with the Exposure and DRX controls, and where you can assign the target color profile for output. You can even output a test file or sequence here, although it’s not recommended for converting multiple sequences; there are better tools for that.
If, for example, you have been taking advantage of Final Cut Pro’s ability to edit the QuickTime movies that link to R3D files, there are several ways to get your EDL to where you can convert those files, with handles, to a format you can use. One of these is Monkey Extract, whose free version lets you do the basic conversion to DPX, TIFF, or even QuickTime, without all the geeky unfriendliness of Crimson Workflow (also free). Granted, an XML-based EDL limits you somewhat: multi- and sub-clips may typically be off-limits or require a work-around.
However, this approach allows you to convert the R3D to a file that has no less color data than your source, and no greater resolution than you need for your output. Again, if you weren’t reading carefully, the RED camera records 12-bit images, so a 16 bit linear TIFF or 10-bit log DPX has more than enough headroom to handle the image data at a fraction of the R3D size. Even a carefully written 10-bit linear 4:4:4 image can effectively have no less data than the source; at some point (again, later, tests in hand) I will attempt to explain more about how to unlock the true dynamic range of an R3D.
Meanwhile, if you need to convert to 10-bit log DPX files, Glue Tools allows you to continue to work with them in Final Cut Pro. If you’re on Avid, you can find more information about the RED workflow here (at this writing I personally have no hands-on experience with RED in an Avid workflow).
In Summary
These 5 tips are merely a starting point for more discussion. Overall, keep in mind that although conversion of R3D files requires expertise to be done right, and can require extra days of post-production depending on the size of your project, not to convert if you have that option (working with native R3D files in an application that can handle them such as Adobe After Effects) can cost you much more in terms of slower and less stable workflow as even the most powerful system struggles to work with an image sequence made up of huger-than-necessary frames.
If there’s one key take-away from this article, it’s this: for the vast majority of projects, preserving full 4K (or even 3K) data is not your main goal; you will find the greatest success by converting to a format that keeps only what you need.
(Comments, questions and complaints most welcome - they will help shape follow-up articles)
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>you can even create a color look in REDAlert or >Scratch and transfer it to an SD card to load it >directly onto the camera as a preview LUT.
>Many people don’t know this, and so it is the >rare shoot on which this happens.
http://www.reduser.net/forum/showthread.php?t=24810
http://www.reduser.net/forum/showthread.php?t=25905
You can only save and load looks created in camera. You can re-name those look files on a computer but cannot load a .rsx or .rcc file from redalert or redcine. I can’t speak on for the Scratch software, because I don’t own it.
Red says these feature will happen in the future.
http://www.reduser.net/forum/showthread.php?t=10060
Post #3
Posted by .(JavaScript must be enabled to view this email address) on 03/20 at 12:02 AM
“Take control of sharpness, noise & more during conversion; don’t leave these to tools that can’t work with them”
Not sure if this works too well with vfx plates. We require unsharpened images, untreated as far as possible (though of course we can’t work with raw un-debayerized). For us, things works much better if the tweaks necessary for making the RED images look nice and crisp on the big screen happen downstream from us, NOT during the conversion out of RED raw into dpx or whatever.
This is what we did for the vfx on upcoming feature “Tormented” and it all worked very well.
Posted by paddy on 03/20 at 06:28 AM
I’m gonna test creating on camera looks this week and will post what I find - thanks Steve.
Paddy, I understand the age-old habit of lowest possible sharpening on VFX plates, but I’ve found that some artists rely on the downsample to a lower res to do the sharpening “automatically” and that seems wrong given that a Bayer image needs sharpening. Do you stay at 4K and sharpen at the very end?
mc
Posted by Mark Christiansen on 03/23 at 10:34 PM
“age-old habit?” Hmm - well, not quite the phrase I’d choose, but anyway…
Given that sharpening is only ever a trick to give a greater subjective impression of detail, without actually providing any additional information, it is certainly best left to the end of the image chain if vfx are to be involved. We don’t want to have to emulate the sharpening artefacts alongside everything else we do! Also - sharpening affects the image in non-obvious ways. It can make motion tracking much harder. It can make keyed edges noisier, etc.
Regarding what you say about using the interpolation filter when downsizing to add sharpness - I always recommend a “box” filter as the best choice. No fake sharpness, no aliasing, no ringing edges. It’s the most “honest” downsize, if one can put it that way.
On Tormented, all the sharpening did happen at the end - in the DI realm, so I have no detailed knowledge of what they did. But the editor and director are both highly tech savvy ( http://www.4klondon.com/ ), and I have no doubt they made a good choice.
In the vfx area - we did take some plates in at 4k - for instance if we were going to be zooming into any plates and applying post camera moves.
But the majority of the show was done with RED plates exported to us at 2048x1556 digital anamorphic. We horizontally squeezed the 4k raw 2.35:1 image to fill a 2048x1556 4:3 frame. Thereby doubling the vertical resolution of a standard 2k export.
The images looked a little on the soft side, compared, for instance with the aggressively sharp and grainy images I have seen from the ARRI D21, or some film scans. But nevertheless - very good. And, as they were very clean and low noise, I’m sure the DI sharpening options at the end were very good.
I have no doubt the film will look extremely good on the big screen.
Posted by paddy on 03/24 at 04:37 AM
If your interested in using/working with LUTs, and if you’re using Red you should be, have a look here:
http://www.lightillusion.com/usingluts.htm
Once you grasp this a lot of the ‘mumbo-jumbo’ vanishes.
And this may alos be of interest - just my views on working with Red:
http://www.lightillusion.com/redworkflowissues.htm
Steve
Posted by Steve Shaw on 03/27 at 04:01 AM
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