Alexa post - Log-C, LUTs, best practices

I've got three calls since morning from editors in prominent post houses - one with offices in LA, Vancouver, New York... yeah, yeah we know... and another with offices in Bandra, Andheri, Chennai, London… 

Complaining that Alexa footage looks 'milky and low contrast'.

I had written earlier about struggles in digital movie-making

http://neilsadwelkar.blogspot.com/2011/05/struggling-with-digital-movie-making.html

And on Arri Alexa Avid workflow

http://neilsadwelkar.blogspot.com/2010/12/arri-alexa-avid-workflow.html

Some details on the Alexa camera itself here…

http://neilsadwelkar.blogspot.com/2010/05/arri-alexa-digital-movie-camera.html

Here are some simple facts…

The Arri Alexa camera can shoot 'linear' (technically called Rec.709) which looks 'normal'. Or as LogC which looks 'milky and low contrast'.

LogC gives you more latitude. Which, depending on the calibre of the cinematographer, means, he can mess up the exposure and you fix it in post, or he can shoot amazingly and you can change the 'look' and better it in post.

On the set you can shoot LogC (milky) and yet monitor Rec709 (normal). So, many people get fooled into believing what's on the monitor is being recorded.

LogC need to be converted before you can see them normally.

Avid has no method of doing this logC-linear ('milky' to 'normal') conversion.

In FCP you can get Nick Shaw's plug-in for $ 30 (Rs 1500) and apply it to all clips.

But it is 8-bit and not for production.

Alternately you can download a LUT for the Log-C to Rec709 conversion from Arri's web site. Google 'Arri LUT generator' and you'll find it. And also Arri's excellent white paper on how it all works.

You can also use Resolve, or the free Resolve Lite to do this conversion. Download it for free from Blackmagic's web site, struggle with it for a few hours, and then get an expert to do it for you.

Best of all, if you're shooting for TV, and you really don't want to mess with this Log-C business, just shoot linear or Rec709.

About the data coming out of the camera (can't call it 'footage' any more)

Alexa shoots HD 1920x1080 on memory cards - called SxS cards.

or it can shoot '3k' to a Codex digital recorder.

or it can record out to as video to an HDCamSR VTR on to HDCamSR tape.

On memory card it shoots Quicktime movies in the Apple ProRes4444 format.

On the Codex it shoots ArriRAW files that have to be converted before you can edit them.

Copying all this data to WD, or Seagate or LaCie disks is a risk. A drive fails, you need to reshoot. Period. 

There are two kinds of people - those who have had to reshoot because of a hard disk failure, and those who have yet to reshoot because of a hard disk failure. Carry a piece of wood to knock on from time to time if you are the latter.

Or, hire someone to do data management for you. Whatever you decide, don't let the post house manage your data. And never leave your data on someone else's hard disk. It is vastly easier to browse, copy and use anyone's data in a post house's shared hard disk - than it used to be in the 'film and video tape' days.

For data storage on movies I'm currently working on - Canon7D, Red, or Alexa, TV or cinema or commercials - I'm currently using RAIDs from Sonnet, G-Tech, and Maxx. All are good. And safe. I also advice backing up to LTO tape for long term storage.

On backup for all this media, I've written about this a while ago, but the basics remain the same…

http://neilsadwelkar.blogspot.com/2009/12/backup-for-tapeless-media.html

In terms of disk space…

Shooting HD as ProRes4444 uses up about 140 GB per hour of shoot, 

ArriRAW does it at 10 GB per minute, or 600 GB per hour.

ArriRAW has more resolution and latitude than ProRes4444, but at a cost.

There's only one Codex recorder that can shoot ArriRAW, in India, so far.

If all this sounds complicated, it really is just a bit. If you'd like peace of mind, do all that I've recommended and you're safe. 

Arri Alexa Digital Movie Camera

At IBC last year, Arri announced a new camera. A successor to the D21 - a digital camera to shoot movies with. That was Sept. 2009.

 

Last week at NAB (a large international post-production exhibition and conference at Las Vegas) Arri showed the camera. Its now called Alexa. Arri had a working prototype at their booth. Something you could touch and feel and shoot with and watch the output of, on a HD monitor.

The most important thing Arri have done with the Alexa is to sort out the production and post-production workflow in a manner that's simple - probably simpler than the Red. Whether this helps them sell well and better then Red, only time will tell. The pricing is not a bit higher than the Red, though.

In it's base configuration the Alexa shoots at a resolution of 3 k with a frame size of 3072x1728. This is downsized to HD at 1920x1080 and recorded to SxS memory cards as Apple ProRes422HQ or Apple ProRes4444. ProRes422HQ has a data rate of 145 Mbps while ProRes4444 has a data rate of 330 Mbps.

To put this into perspective, Panasonic D-5 tape stores video at 220 Mbps and Sony HDCamSR does 440 Mbps. So, in terms of data rate, and hence arguably, quality, the Alexa at ProRes4444 is somewhere between D-5 and HDCamSR.

This HD output is also available as a HD video signal which can be recorded to HD video tape like HDCam or HDCamSR. In fact, this is a safe way or working. ProRes4444 on SxS cards and the same HD video to HDCamSR tape. The tape becomes a backup.

For even higher quality and latitude, the Alexa also can record Arri RAW to a certified Arri T-link recorder. Like the Codex, S.two, or KG models of recorders. These recorders cost as much or more than the camera.

When the Alexa makes its way into India, the scenario might look like this...

The camera itself (pro set with DTE option) costs about Euros 52,500 (about Rs 40 lakhs incl. Customs Duty). And the recorder that can record Arri Raw costs another US$ 60,000 (about Rs 36 lakhs incl. Customs Duty).

The Arri Raw recorder records to hard disk about 15 Gb per min. So, if you are shooting a feature film of 120 mins at a shooting ratio of about 5:1, you need about 9000 Gb or 9 Tb space to store 10 hrs of Arri Raw rushes. At a shooting ratio of 10:1 which is what people do, when they shoot digital, you're looking at 18 Tb. To be safe you need to back this up in two sources - disk and LTO.

Now, going by what non-film cameras like the Red rent out for in India, my guess is that the Alexa will also rent at a premium. Meaning you will need to shell out two times or more per day for an Alexa what you would, for an Arri 435 film camera. This differential alone will make potential film-makers think twice about shooting digital.

Add to that the FUD (fear, uncertainty, doubt) factor around digital, it will take a while for someone to have the guts to do an entire mainstream film on a digital camera like the Alexa. As if that isn't enough, the sheer cost of providing safe secure storage for digital Arri Raw data, will make most producers balk at the idea.

At a conservative estimate, 8 Tb of safe secure RAID storage will cost at least Rs 1,20,000 for an 8 Tb RAID. That will add up to Rs. 2,40,000 for 16 Tb. This cost will need to be borne by the producer as well. Of course after the film is done, one can delete the unused rushes and then reuse the storage for forthcoming films. But the initial acquisition of a high quality disk storage will have to be made.

Many film-makers may settle for Apple ProRes4444 which takes up just 130 Gb per hour, or 1.3 Tb for 10 hours going up to 2.6 Tb for 20 hrs. And, for many purposes, ProRes4444 provides nearly all the bandwidth and sheer picture quality that Arri Raw would have given you, but at a fraction of the disk space and bother of file conversion.

At NAB, I was told, about 300 Alexa cameras were sold worldwide. In all probability, one or more people from india have bought one, or are considering one. So, come June, when the Alexa ships, one will see an Alexa somewhere in India, most likely in Mumbai.

For someone looking at an alternative to film, and who doesn't want to mess with the workflow of Red because his editor or cinematographer has heard bad things about it. And needs a camera that responds just like a film camera - the Arri Alexa is a good choice. If you have the budget and inclination for shooting Raw, and a recorder is available, then go with shooting Raw.

The complete Arri Alexa specs ...

There's, of course, more to the Alexa than just post-production convenience. Its latitude, dynamic range, 35mm sized sensor and compatibility with existing 35mm film lenses. Features that might appeal to the cinematographer and make the camera closer to a film camera. There isn't (yet) an optical viewfinder, but they may add one later in the year.
 

But for ease of use and simplicity, stick with shooting ProRes4444. The files will open and can be edited directly in FCP. And even in Avid Media Composer ver. 5.
After editing, these files will open directly in Smoke on a Mac for any effects work. Even windows apps like 3DStudio Max can use these files for any CGI work. For grading, the yet-to-be-released Resolve on Mac will be able to grade ProRes4444 files.

So there you have a clean and simple workflow. For shooting digitally for features and shorts. Even ad films and music videos.