What is the secret to Final Cut Pro X’s color management?

In the mid 1990’s my Australian company made the decision to purchase a Media 100 system. That remains the best business decision I ever made (and selling it to jump to Final Cut Pro 1 was the second best business decision). It also meant we were migrating from Amiga computers to Macs. Given that I already had a graphic designer on staff for titles, illustrations and animations, I decided to delight clients by having our designer create a full color slick for the (then) VHS deliverables. (Masters simply got descriptive labels.)

Until that point we’d only done black and white printing, and it’s easy to proof what you’re going to get on a B&W laser printer. Not so with color. Color output wasn’t as common then as it is now and we didn’t get the first Kinkos until very late in the 1990’s, so we really only had one choice for our runs of 2-3 covers for each job.

This became a serious problem when – while developing a food product for my parent’s company during the period I managed it (in addition to my own two companies) – we needed a very specific purple on mockup packaging we were presenting to food buyers at the national department store chains in Australia. Cadbury – Australia’s biggest chocolate company – have always used a specific purple in their packaging, and had just spent several million dollars on a campaign that heavily featured this purple. Since the new product was a chocolate variation on a traditional English Christmas Pudding, having the purple match was beyond important. And we got blue-purple, and red-purple: seemingly every color except the one we wanted.

The problem was, what we saw on the screen and what they printed were two entirely different images. Just like that, the print industry’s color management problems were now my color management problems. There’s nothing like first hand knowledge of the problem to appreciate the cure!

By early 1998 we were full on into publishing, with the release in February 98 of the Media 100 Editor’s Companion. By this time we had  learnt – although that particular output bureau never did – the joys and benefits of ColorSync. While the interior was done with xerography (i.e. photocopying) the color covers were done in Sydney by a direct-to-plate digital offset and we never ever had color accuracy problems with an output bureau that used ColorSync.

ColorSync was the solution the print industry needed to deal with color consistency and matching. The challenge is quite significant when you consider that each device treats color slightly differently: they have different “color profiles” in ColorSync Profiles. What ColorSync facilitates is a color accurate workflow, also referred to as a color managed workflow.

The challenge in print is to ensure that a scanned image reproduces with correct colors on an RGB display and prints consistently on a wide range of types of printers (and size of output) in CMYK color. On computers the images are additive (three light sources) while on paper they are subtractive.  If you worked hard you couldn’t create a less consistent workflow.

And yet, for the last 15 years or so, this has not been a problem. Colors in Photoshop, Illustrator, InDesign, Quark, etc. are accurately reproduced in the final output despite the different color models, device variations, display variations, differing types of paper and even ink variations. This has been possible because of ColorSync, largely developed by Adobe and Apple but now supported on every platform and by all manufacturers of scanning or printing hardware.

What is ColorSync?

This I knew when I wrote recently on how ColorSync might be used as part of Final Cut Pro X’s color management, but from the comments it quickly became obvious that I was very uncertain about:

• How does ColorSync work with video files, and specifically
• How does Final Cut Pro X use ColorSync to accurately monitor color.

So I took it upon myself to start researching the topic. I very quickly discovered that, while there is a lot of information regarding ColorSync and printing workflows, there was really nothing about ColorSync and video short of an OS 9 era article on ColorSync and QuickTime, noting that we can add ColorSync profiles to QuickTime movies using Terran Interactive’s Media Cleaner Pro! (That really dates it. Neither company nor product still exist.)

I took the opportunity to ask my contacts at Apple some specific questions about how ColorSync works in Final Cut Pro X and then synthesized that with the best information I could about ColorSync in general to research what I found. What was also interesting is that, while ColorSync has been mentioned in the PR materials and demos, there has been no explanation as to how that facilitates accurate color. This is my attempt to redress that lack.

ColorSync is built on ICC profiles and the two  terms are interchangeable: an ICC profile managed workflow is a ColorSync managed workflow. Each device – scanner, printer, camera, monitor – has at least one ICC profile. In an oversimplified explanation the ICC profile tells ColorSync (or equivalent engine in Adobe’s applications) how this device’s color representation differs from the standard. In this case it’s the XYZ Profile Connection Space: a colorspace with a very wide gamut.

So, for a given scanner the ICC profile is used to create an accurate representation of the scanner’s result into the Public Connection Space (PCS from here on) and the display’s ICC profile tells ColorSync how to accurately display that PCS on that specific monitor for most accurate fidelity to the original image content data.

In simple terms each device tells ColorSync how that device’s files relate to the PCS either to convert to the PCS or convert from the PCS to a display or printer. This way, each display or printed copy is color accurate to the original file, despite variations in printers or displays.

Workflows that correctly follow this practice are known as Color Managed workflows.  (Check and see if you’re reading this in a color managed browser.) From that page:

This is happening BECAUSE your color-managed browser is reading each file’s embedded profile and Converting or Mapping them to your monitor profile for a theoretical display of True Color.

In practice, while you may have to set up Photoshop or some other tools, for the most part, like the color management in Safari demonstrated from the link above, it just happens. You’ll find scanners and printers install ColorSync (ICC) profiles for all the functions – a scanner/printer will have a scan-to-PCS profile, and a PCS-to-printer profile – and OS X uses them.  Earlier versions of the OS required some setup but recent (10.5 onward at least) have implemented ColorSync so it “just happens”. As long as each device has a profile, and files are tagged with the appropriate source ICC profile, color accuracy along the entire process is assured.

Color consistency in the video world

Meanwhile, it was easy to monitor video: use a calibrated video monitor. Connect output of your edit system to said calibrated monitor. If you were very particular about your video signal you connected Waveform and Vectorscope to the output as well, so you could really see what’s going on in the signal.

The accuracy of the color entirely depended on how good a monitor you put on the end of the chain. Now in a perfect world this would be a broadcast level monitor, calibrated at least once a year, that could be relied on. I confess, I never had one, even though I delivered a decent number of TV Commercials for national TV broadcast, and other content that went to air. The majority of my editing career, however, has been for non-broadcast purposes.

Even today, I support systems that do work for major studios and none of them have a broadcast grade monitor, let alone calibrate it. One system is finishing HD footage to a 10+ year old SD TV set of no particular brand. Another restoring historic footage works primarily with a decent (but domestic) Plasma display that’s distinctly off axis from the editing position.

I’ve set up movie edit stations that have monitored on a Cinema Display via an AJA SDI to DVI adapter (with CLUT); or to an LCD TV. In fact that device is doing in hardware exactly what ColorSync is doing in software. Now these movies were not graded on this system, just for editing so that’s probably fair. Another client working on a TV series  for Cable Networks, has only a broadcast monitor (JVC 24U) in the grading room; the other four bays all work with consumer LCD or Plasma.

Color fidelity required that the NLE made no unintentional changes to the signal coming in and ultimately the accuracy of color depended entirely on how accurately the specific display represented the colorspace it was attempting to represent. In SD that would normally be Rec. 601 and for HD normally Rec 709.

It’s up to the NLE software to convert colorspace from the different source profiles it encounters: not only Rec 601 and 709 in video files but sRGB or any of another dozen possible profiles for still images.

This type of monitoring – a conventional video output – allowed monitoring in the destination colorspace, but appears to be not part of Final Cut Pro X’s design, at least according to Matrox. So, how does Final Cut Pro X ensure color consistency? Of course, ColorSync.

ColorSync was implemented in QuickTime. Badly. Final Cut Pro 7 did not support it, instead working with it own color conversion/matching technology.

Final Cut Pro X and ColorSync

As I’ve discussed the important considerations for ColorSync are:

• The colorspace, which can be considered to be the equivalent of an ICC profile, must be known and accurate for the file (taking the place of the source device profiles in print workflows);
• The rendering engine must use ColorSync to convert from source to destination colorspace/profile;  and
• The frames must be converted for the desired output, be it a Cinema Display, SD 601 or HD 709 result.

This is exactly what Final Cut Pro X does.

As files are ingested, Final Cut Pro X will read any ColorSync information if the files are tagged with information about their colorspace. If it’s a QuickTime file that contains an explicit tag for color information, that is respected by Final Cut Pro X, Motion 5 and Compressor 4.

If there’s not an explicit tag, then Final Cut Pro X infers the colorspace from known information. For example DV files automatically imply either an NTSC Rec 601 colorspace or a 1280 x 720 or 1920 x 1080 file will be tagged as being HD Rec 709 colorspace. These are quite reasonable assumptions and yet another use of Inferred metadata in the Final Cut Pro X world. Beyond those examples, Final Cut Pro X will simply make an intelligent guess based on whatever information is available. Fortunately, image size and aspect ratio are very strong clues to how the source color should be interpreted (the purpose of tagging it). 720 x 576 pixel files are almost certainly PAL SD files and so Rec 601 PAL is reasonably inferred.

Generally it’s older files that have no useful information and require inferring colorspace, but since there really are so few colorspace choices for video, compared with print where each device has its own characteristics, the source ColorSync information is likely to be highly accurate.

I’m sure someone will take me to task on the fact that Rec 601 doesn’t fully describe the color profile because there is no primaries defined, but Final Cut Pro X uses other information in the file to determine which of the well know primaries should be associated with the file.

So we have source color profile information associated with the files. Now it’s up to Final Cut Pro X to ensure that the rendering is accurate.

For Final Cut Pro X and Motion Apple created a shared render engine, touted as the “Linear Light Engine” at the NAB Supermeet Preview but that branding seems to have been dropped ahead of release. This shared render engine uses ColorSync to conform an image from one colorspace to another. ColorSync creates the steps that are required for a specific transform and then assembles them into a series of GPU operations into the GPU processing pipeline. Or in simpler terms, it manages the transforms so the source image content is accurately represented into the processing space.

There is no assumption about the input colorspace at render time. ColorSync profiles were derived or inferred on ingest or come from the image file. Most processing uses the Rec 709 primaries with a linear (1.0) gamma, ready for the final stage.

The third point above, is that the render engine has to accurately prepare that processing space for the appropriate output. If outputting to a Cinema Display, then the render engine conforms the processing space so that the visual appearance on the Cinema Display will look like the image should be viewed. (This works well with the recommended gamma and color temperature for the display: 2.2 and 65oo K respectively.) For the most accurate results you’ll want to create a ColorSync profile for the specific monitor rather than using the supplied “generic for this type of monitor” profile that ships. You can use the ColorSync Utility for that, or a tool that reads values off the screen to generate the profile.

If you’re working with an HD Rec 701 file but request an output for DVD, then the 701 frames (and other graphics from their colorspace) are converted and output so they are correct for the Rec 601 colorspace of a DVD.

So Final Cut Pro X determines the colorspace (ICC Profile) of the source on ingest; manages color using ColorSync through the rendering engine and then uses ColorSync to make sure that the representation on the display – whatever type of display – is also an accurate representation.

Meaning, there is no need for an external broadcast monitor in the classic sense. What you see on a monitor that has a ColorSync profile, is an accurate representation on that monitor of the source colors displayed on a Rec 709 monitor. And you don’t have to do a thing to get the goodness!

Not convinced? Well, coincidentally the Academy of Motion Picture Arts and Sciences’s “ACES or Academy Color Encoding Specification” initiative is planning something almost identical to ColorSync, but specific to the needs of motion picture post production, particularly with so much digital manipulation and inclusion of digital elements. (Look for the heading “ACES: Academy Color Encoding Specification”).

Beyond Rec 709

While the ACES initiative is largely about colorspaces used in digital cinema, it should be pointed out that a “broadcast video monitor” would be no help for colorspaces other than Rec 709 (for HD). So if you want to work with, DCI-P3, also SMPTE-431-2, for example in a traditional NLE you’d be stuck previewing in the wrong colorspace.

With a color managed/ColorSync workflow, if you have DCI-P3 media, and the appropriate source ColorSync/ICC Profile (or colorspace definition,) then ColorSync in Final Cut Pro X would present an accurate representation of that source on the computer monitor.

Mixing any of these colorspaces into any one, and then outputting the appropriate colorspace becomes no problem when using ColorSync.

Conclusion

While it’s a significant change from traditional workflows, the approach taken by Apple with Final Cut Pro X is a better fit for what happens in edit bays outside the big studios, where the problem with early Final Cut Pro users wasn’t that they weren’t monitoring on calibrated broadcast monitors but that they were monitoring only on the computer display. How many times did I, and the other Final Cut Pro 1 pioneers have to remind people that the computer display is not an accurate representation of the video!

Well, 2.2 gamma on OS X (since Snow Leopard) and ColorSync have made that advice not only null and void, but downright wrong. With a ColorSync workflow, the view on the computer monitor, particularly in full screen mode, will be more accurate than using a consumer television as a display, with the sole exception of interlaced video output. If you’re delivering for web, for LCD or plasma screen (i.e. all currently available displays) the display is progressive. Produce and edit accordingly.

I don’t think we have broadcast video output from Final Cut Pro X, because we have something better that accommodates todays colorspaces and will expand to accommodate whatever the future holds as well.

A disclaimer. I do not have the equipment available to test this: I don’t have a broadcast monitor nor a system that could output to it via SDI or even analog. (I could do DV via Firewire, but really….) I am confident that the solution that solved my inconsistent print color issues is robust enough, with the right software design, to manage my consistent video image needs.

The purpose of monitoring video on a broadcast monitor is to ensure that we have consistent color accuracy from a known reference. The value of a ColorSync workflow is that we ensure that we have consistent color accuracy wherever its shown. It’s a superior choice that avoids the limitations and expense of the previous “standard workflow.” Instead of having to build in a single colorspace on a monitor, Rec 601 or 709 style, with ColorSync all wide gamut monitors can be calibrated (ideally with a colorimeter and on that specific monitor) and used as reference monitors.