Dailies from Alexa LogC ProRes

A question buzzing around right now is to figure out what the best way to create watchable dailies from the Arri Alexa when you shoot in LogC format with ProRes 4444.  I've done a lot of sniffing around, and there just isn't an easy desktop answer to applying a LUT when you do a mass transcode of your camera original files.

Compressor?  Nope.  Episode?  Looks like it had a RGB to YUV LUT function in previous versions, but not currently.  Gluetools?  Nope.  Silverstack? Looks like it will, but it isn't released yet.  Clipfinder?  Heard a rumor a LUT transcode is in the works, but no official word. Avid MetaFuze?  It has the option of applying a LUT when converting from DPX, but not for converting from Quicktimes.  Assimilate Scratch does a great job making dailies like this, but generally you only find that at a professional post house.

So for the DIY crowd, here are a couple of your desktop software options, first Final Cut Pro, then After Effects.

One of the guys on top of it all is Nick Shaw of Antler Post.  He made a Final Cut Pro plugin that simply adapts ARRI's very own LUTs that they made available to the public.  ARRI has currently taken them off their website, however they will be back soon as a LUT generator according to ARRI.

To get the plug-in (currently free), contact Nick Shaw using his website http://www.antlerpost.com.  I could make it available here, but I think he wants to know when people are using it.

Here is your workflow in Final Cut Pro (FCP from here out):

-Import all your camera original files (or import the XML files the Alexa makes with them).

-Drag all the clips end to end onto a Sequence timeline (make sure you say "yes' when FCP asks if you would like to match the sequence settings to the clips' settings).

-Start with the first shot, add the Alexa LUT effect to your clip.  Nick made versions for four different ISO settings.  800 is the standard, but each one basically just compensates a little for exposure.  Note it's not a perfect transformation if your shot isn't exposed exactly in the middle.  If it's underexposed or overexposed, it might seem more-so than it actually is in in the LogC file.  

-Tweak the settings to what you like-- there is the ability to burn in timecode or other chyrons.  There is also a saturation boost, set normally to 1.5 to bring the color up to normal.  (note:  it seems that Arri's 1D LUTs don't change the colors much, and their 3D LUTs change only the colors and not the gamma curve.)

-I experimented with adding a "gamma" adjustment effect before the Alexa LUT effect.  This seemed to quickly get me close to where I want to be with the exposure.

-Once you're happy with the effect settings, "Copy" the clip, select the rest of your clips in the sequence timeline, "Paste Attributes' and make sure "Effects" is checked.  Now all your clips should have the LUT applied.  You can feel free to tweak individual shots if you feel it's necessary, or even add other color correct effects yourself (maybe an exposure correction before you apply the lut).

-Now select all the clips in your sequence timeline, and drag them to the "Export Queue" (from the Window menu).

-The Export Queue will render all your individual clips using the Effects settings you just used, as well as keep your timecode and logging information intact to the new transcoded files.  In the Export Queue window you can set what format to transcode all the clips to (keep your clips selected), as well as what folder to export to, and even some naming options.  I recommend ProRes 422 HQ to stay in 10-bit colorspace, but honestly regular ProRes 422 (8-bit) is a great option as well, and will save a lot of drive space and work a little faster.

Suggestion: You would probably do yourself a favor down the line to keep the file names the same, and then pull your ProRes 4444 LogC footage onto a backup drive that you will later disconnect.  That way when you get to the finishing process (online), you can simply re-plug in your ProRes 4444 LogC footage drive (disconnect the ProRes Rec.709 footage), and do a "Reconnect Media" so that you will be back in LogC world before you (or your DI specialist) do the final color correction.  Don't keep your ProRes HQ dailies and ProRes 4444 dailies in the same place though, because then FCP might connect to the wrong media accidentally, since the names are the same.

Rendering time seemed to be about 1 to 1 (real time) using an 8-core MacPro.  Unfortunately FCP rendering is not multi-processor enabled (much, anyway).

You can also edit the LogC footage directly using Nick's plug-in.  It should work real time using the RT engine, but you should set the Frame rate to "Full" (usually Full) and the resolution to "Full" (usually Dynamic).  It played back fine in full frame rate and resolution with a yellow bar on an 8-core MacPro.  I don't recommend editing a long project this way, as it'll slow you down.  Better to get the transcode out of the way before you start.

Now a couple notes about it in After Effects CS5.

LogC is designed to work like a Cineon file (DPX) encoded in Log.  So therefore After Effects "Cineon Converter" effect works wonderfully, even at the default settings.

I was also pleased to see a new effect in CS5 that says "Apply Color LUT"  It uses 3d Luts (.3DL) ARRI's Fusion logC2film 3DL lut works just fine.  I applied that effect first, and then applied the Cineon Converter with the default settings.  It looks great even before tweaking, though you may want to adjust your black, white points and gamma, along with highlight roll-off.  The most effective way I could see how I was affecting the image was to lay a "levels" effect after it (no adjustments to it), and just using it to look at the histogram as I adjust the cineon settings.

Now how to automate this conversion?  That's another story.  Certainly you can quickly create a bunch of compositions and add them to the render queue (drag all your imported clips over the composition icon in the project window).  But then you would have to go into every composition to paste the effects settings onto every clip.  I'm sure there is a way to use AE's scripting engine to make this go much faster, but it would take some work putting that together.

The programming crowd is out the scrambling for a cleaner, automated system, and I can't wait until its ready.  Until then, I hope these suggestions are helpful.  If you've figured out your own system, please let me know below.

Andrew Wahlquist

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