120 fps to ProRes HQ recorded right to on-board SxS media. There is no sensor windowing to achieve this higher frame rate so no change in Depth of Field, Field of View, or Dynamic Range. I was under the impression that this functionality would be arriving very soon but no time frame has been set other than "later this year".
June 3, 2011
The Alexa has all but taken over commercial and episodic production. Why is that?
Simple - Direct to Edit.
ProRes 4444 is a fantastic compression scheme with ample color information for grading. Combine this with the extended dynamic range of Log C and you've got a winner. PL lenses, Super 35, a camera department friendly build, and beautifully rich video that doesn't need to debayered. Arri saw the writing on the wall and commercial production quickly agreed.
ProRes 4444, or simply ProRes 4x4 has a bit depth of 12 and is a full sample of both red, green, and blue. Is this the best option in terms of image quality you can get from the camera? Not compared to uncompressed or raw but as it's been proven time again, definitely adequate for broadcast.
There are 3 ways you're likely to work with the Alexa -
1. ProRes 4x4 on-board recording to SxS cards, probably in Log C. Paint LUT's on-set that the colorist will use as a starting point for dailies creation. Or use those LUT's to make the dailies on-set yourself with software like Scratch Lab or Resolve Lite. Every DP has their own preference of how they intend to use your on-set correction but the savvy ones realize it's an opportunity to take establish the look of the project on the set while there is still time to change exposure and camera settings.
2. Dual Link 444 Rec Out to external deck or recorder, most likely Sony SRW-1 but with the ongoing tape stock shortage, this is becoming more uncommon. Or use an uncompressed recorder which will result in 1920x1080 DPX image sequences. One 512 GB mag will hold about 40 minutes of uncompressed footage so in terms of post production infrastructure, the uncompressed world is a far more data intensive place than ProRes. Uncompressed HD is fantastic stuff and prior to Arriraw implementation, this method was the highest quality the Alexa could deliver. But not the biggest raster.
3. And now, Arriraw, which can only be recorded 2 ways - with the Codex and the S.Two OB-1 - both solid state recorders that rent for the same price as the camera. I'm not a huge fan of the OB-1 but the Codex is awesome and the Virtual File System is one of smartest ideas ever implemented for file based workflows. There's plenty of info on that on their website so not going to get into it here. Arriraw is the only way to open up the sensor's native "not quite" 3K resolution.
Arriraw is..
Recorded via Arri "T Link" which is another name for Dual Link. Recorders must be Arri Approved and as of now, there are only 2.
1 frame = 7 MB
1 second @ 23.98 = 168 MB
1 minute = approximately 10 GB
1 hour = approximately 600 GB
It is 2880x1620 pixels and is 12 bit Raw Bayer Data
Ignore the muppet by the chart. Needed a skintone and couldn't find a victim.
Log C with camera metadata (ISO and White Balance, both freely adjustable after the fact)
Rec709 look with no adjustments. This is an uncompressed 3K DPX frame (well.. a jpeg made from that)
When you go from Arriraw to DPX, your file sizes triple so have a few of those 6TB G RAID's handy. 1 minute of Uncompressed 3K DPX frames from Arriraw is almost 30 GB. 1 hour is almost 2 TB. The infrastructure and associated costs required to handle this much data is far beyond the means of most productions so it's something to be aware of.
ARC - ArriRaw Converter. Freeware. This is how you turn Bayer data into something more useful. All image parameters are adjustable.
Arriraw is truly raw with an added advantage - unlike that one camera that shoots a very aggressively compressed raw, this is completely uncompressed. 100% imaging potential is what it should be called.
So you're a producer and you're weighing your options, trying to figure out which is best for your show - ProRes, Uncompressed HD, or Arriraw. How do you decide? There are some many factors to consider and it's not always an easy conclusion to come to. Productions with substantial resources who could afford to go uncompressed often opt for ProRes because it's the easiest and honestly - good enough for tv. Arriraw is superb but probably overkill for a lot of applications. It's got feature film written all over it though.
On the horizon -
As of v4, 120fps to SxS cards in ProRes HQ. I've seen the demo and it's fantastic. No sensor windowing means no difference in angle of view and depth of field between your off-speed and sync sound shots. These new 64GB Sony SxS cards have significantly improved throughput and are requisite to doing 120 fps shots. Because these new cards have ample storage, theoretically holding about 5 minutres of Arriraw and can write at speeds faster than it requires, you can put 2 and 2 together as to what might be in the pipeline.
That was an exceptionally nerdy post so I think I've met my quota for awhile. Have a great weekend.
I'm often still a little shocked at just how light sensitive the Alexa really is. When I'm at my cart evaluating images shot with a fast lens at ISO 800, they are often far brighter and better defined than what you see on-set with your own eyes. When the gaffer is wishing he had 40 watt open face lights, you know you're in a brave new world. Working at such a low foot-candle becomes challenging in new ways and as I've discovered, there are a few fascinating side effects.
Red Eyes in Motion Picture - an effect that used to be very difficult to achieve on film is now far easier. For better or for worse.
When your key light source is a scant 3 foot-candles, the human eye naturally dilates considerably to accommodate such low light. When you have a source close to the lens such as a ring light and your subject's pupils are in this state, you can very easily end up with eyes that look like something like this (model on the right) -
Alexa v3 @ ISO800, Cooke S5 @ T1.4, 2.75 Foot-candles
As we associate red eyes with cheap stills photography, seeing this effect in motion pictures is truly strange. The only work around is work at a higher foot-candle so the talent's eyes can adjust or to keep all your sources away from the lens.
Very interesting stuff.
Here's something else I've noticed. When you're working low light like this, the DP often wants to put ND gel on the lights themselves so to avoid dimming and color temperature shift. When you have 2 or 3 layers of this stuff on any head - tungstens especially, you will invariably need some minus green gel as well as lots of ND will usually pass more green light than red and blue. Finding the green in the scene becomes a new challenge. One more thing to keep that critical eye on the look out for.
On an Alexa related note - my fav on the fly color correction app, LinkColor, just got an update and can now import Iridas cubes from the Arri LUT Generator. I've been using Arri's basic 3D Log to 709 as my starting point as the contrast in this LUT matches what the DP is seeing on the Mon Out on the camera. This has worked out great because if he/she likes the contrast they see on their on-board monitor, you can now very easily match it on your correction with this LUT and then tweak from there. It's a great way to begin your look.
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