When Does Color Correction Happen?

A program’s color fidelity shouldn’t be neglected until the color correction stage of the post-production process. Ideally, every project is begun with a philosophy of color management that’s applied during the shoot, is maintained throughout the various transfer and editing passes that occur during post-production, and concludes with the final color correction pass conducted in Color. This section elaborates on how film and video images have traditionally made their way through the post-production process. For detailed information, see:

Color Management Starts During the Shoot

Whether a program is shot using film, video, or high-resolution digital imaging of another means, it’s important to remember that the process of determining a program’s overall look begins when each scene is lit and shot during production. To obtain the maximum amount of control and flexibility over shots in post-production, you ideally should start out with footage that has been exposed with the end goals in mind right from the beginning. Color correction in post-production is no substitute for good lighting.

Optimistically, the process of color correction can be seen as extending and enhancing the vision of the producer, director, and director of photography (DoP) as it was originally conceived. Often, the DoP gets personally involved during the color correction process to ensure that the look he or she was trying to achieve is perfected.

At other times, the director or producer may change his or her mind regarding how the finished piece should look. In these cases, color correction might be used to alter the overall look of the piece (for example, making footage that was shot to look cool look warmer, instead). While Color provides an exceptional degree of control over your footage, it’s still important to start out with clean, properly exposed footage.

Furthermore, choices made during preproduction and the shoot, including the film or video format and camera settings used, can have a profound effect on the amount of flexibility that’s available during the eventual color correction process.

Initial Color Correction When Transferring Film

When a project has been shot on film, the camera negatives must first be transferred to the videotape or digital video format of choice prior to editing and digital post using a telecine or datacine machine. A telecine is a machine for transferring film to videotape, while a datacine is set up for transferring film directly to a digital format, usually a DPX (Digital Picture eXchange) or Cineon image sequence.

Workflow illustration of telecine color correction

Usually, the colorist running the film transfer session performs some level of color correction to ensure that the editor has the most appropriate picture to work with. The goals of color correction at this stage usually depend on both the length of the project and the post-production workflow that’s been decided upon.

  • Short projects, commercials, spots, and very short videos may get a detailed color correction pass right away. The colorist will first calibrate the telecine’s own color corrector to balance the whites, blacks, and color perfectly. Then the colorist, in consultation with the DoP, director, or producer, will work shot by shot to determine the look of each shot according to the needs of the project. As a result, the editor will be working with footage that has already been corrected.

  • Long-form projects such as feature-length films and longer television programs probably won’t get a detailed color correction pass right away. Instead, the footage that is run through the telecine will be balanced to have reasonably ideal exposure and color for purposes of having a good image for editing, and left at that. Detailed color correction is then done at another stage.

  • Projects of any length that are going through post-production as a digital intermediate are transferred with a color correction pass designed to retain the maximum amount of image data. Since a second (and final) digital color correction pass is intended to be performed at the end of the post-production process, it’s critical that the image data is high quality, preserving as much highlight and shadow detail as possible. Interestingly, since the goal is to preserve the image data and not to create the final look of the program, the highest-quality image for grading may not be the most visually appealing image.

However the color correction is handled during the initial telecine or datacine transfer, once complete, the footage goes through the typical post-production processes of offline and online editorial.

Color Correcting Video Versus Film

Color has been designed to fit into both video and film digital intermediate workflows. Since all footage must first be transferred to a QuickTime or image sequence format to be imported into Color, film and video images are corrected using the same tools and methods.

Three main attributes affect the quality of media used in a program, all of which are determined when the footage is originally captured or transferred prior to Color import:

  • The type and level of compression applied to the media

  • The bit depth at which it’s encoded

  • The chroma subsampling ratio used

For color correction, spatial and temporal compression should be minimized, since compression artifacts can compromise the quality of your adjustments. Also, media at higher bit depths is generally preferable (see Bit Depth Explained).

Most importantly of all, high chroma subsampling ratios, such as 4:4:4 or 4:2:2, are preferred to maximize the quality and flexibility of your corrections. There’s nothing stopping you from working with 4:1:1 or 4:2:0 subsampled footage, but you may find that extreme contrast adjustments and smooth secondary selections are a bit more difficult to accomplish with highly compressed color spaces.

For more information, see Chroma Subsampling Explained.

Traditional Means of Final Color Correction

Once editing is complete and the picture is locked, it’s time for color correction (referred to as color grading in the film world) to begin. Traditionally, this process has been accomplished either via a color timing session for film or via a tape-to-tape color correction session for video.

Color Timing for Film

Programs being finished and color corrected on film traditionally undergo a negative conform process prior to color timing. When editorial is complete, the original camera negative is conformed to match the workprint or video cut of the edited program using a cut list or pull list. (If the program was edited using Final Cut Pro, this can be derived using Cinema Tools.) These lists list each shot used in the edited program and show how each shot fits together. This is a time-consuming and detail-oriented process, since mistakes made while cutting the negative are extremely expensive to correct.

Once the camera negative has been conformed and the different shots physically glued together onto alternating A and B rolls, the negative can be color-timed by being run through an optical printer designed for this process. These machines shine filtered light through the original negatives to expose an intermediate positive print, in the process creating a single reel of film that is the color-corrected print.

The process of controlling the color of individual shots and doing scene-to-scene color correction is accomplished with three controls to individually adjust the amount of red, green, and blue light that exposes the film, using a series of optical filters and shutters. Each of the red, green, and blue dials is adjusted in discrete increments called printer points (with each point being a fraction of an f-stop, the scale used to measure film exposure). Typically there’s a total range of 50 points, where point 25 is the original neutral state for that color channel. Increasing or decreasing all three color channels together darkens or brightens the image, while making disproportionate adjustments to the three channels changes the color balance of the image relative to the adjustment.

The machine settings used for each shot can be stored (at one time using paper tape technology) and recalled at any time, to ease subsequent retiming and adjustments, with the printing process being automated once the manual timing is complete. Once the intermediate print has been exposed, it can be developed and the final results projected.

Figure. Workflow illustration of color timing for film.

While this system of color correction may seem cumbersome compared to today’s digital tools for image manipulation, it’s an extremely effective means of primary color correction for those who’ve mastered it.

Note: Color includes printer points controls for colorists who are familiar with this method of color correction. For more information, see The Advanced Tab.

Tape-to-Tape Color Correction

For projects shot on videotape (and for those shot on film that will not receive a second telecine pass), the color correction process fits into the traditional video offline/online workflow. Once the edit has been locked, the final master tape is assembled, either by being reconformed on the system originally used to do the offline or by taking the EDL (Edit Decision List) and original source tapes to an online suite compatible with the source tape formats. For more information about EDLs, see Importing Projects from Other Video Editing Applications.

If the online assembly is happening in a high-end online suite, then color correction can be performed either during the assembly of the master tape or after assembly by running the master tape through a color correction session.

Figure. Workflow illustration of Tape to Tape color correction.

Note: If the final master tape is color corrected, the colorist must carefully dissolve and wipe color correction operations to match video dissolves and wipes happening in the program.

Either way, the video signal is run through dedicated video color correction hardware and software, and the colorist uses the tape’s master timecode to set up and preserve color correction settings for every shot of every scene.

The evolution of the online video color correction suite introduced many more tools to the process, including separate corrections for discrete tonal zones, secondary color correction of specific subjects via keying and shapes controls, and many other creative options.

Color Correcting via a Second Telecine Pass

Programs shot on film that are destined for video mastering, such as for an episodic broadcast series, may end up back in the telecine suite for their final color correction pass. Once editing is complete and the picture is locked, a cut list or pull list (similar to that used for a negative conform) is created that matches the EDL of the edited program.

Using the cut list, the post-production supervisor pulls only the film negative that was actually used in the edit. Since this is usually a minority of the footage that was originally shot, the colorist now has more time (depending on the show’s budget, of course) to perform a more detailed color correction pass on the selected footage that will be assembled into the final video program during this final telecine pass.

Although this process might seem redundant, performing color correction directly from the film negative has several distinct advantages. Since film has greater latitude from black to white than video has, a colorist working straight off the telecine potentially has a wider range of color and exposure from which to draw than when working only with video.

In addition, the color correction equipment available to the telecine colorist has evolved to match (and is sometimes identical to) the tools available to online video colorists, with the added advantage that the colorist can work directly on the uncompressed images provided by the telecine.

After the conclusion of the second color correction pass, the color-corrected selects are reassembled to match the original edit, and the project is mastered to tape.

Figure. Workflow illustration of color correcting via a second telecine pass.

Incidentally, even if you don’t intend to color correct your program in the telecine suite, you might consider retransferring specific shots to make changes that are easier or of higher quality to make directly from the original camera negative. For example, after identifying shots you want to retransfer in your Final Cut Pro sequence, you can use Cinema Tools to create a selects list just for shots you want to optically enlarge, speeding the transfer process.

Other Advantages to Telecine Transfers

In addition to color correction, a colorist working with a telecine has many other options available, depending on what kinds of issues may have come up during the edit.

  • Using a telecine to pull the image straight off the film negative, the colorist can reposition the image to include parts of the film image that fall outside of the action safe area of video.

  • With the telecine, the image can also be enlarged optically, potentially up to 50 percent without visible distortion.

  • The ability to reframe shots in the telecine allows the director or producer to make significant changes to a scene, turning a medium shot into a close-up for dramatic effect, or moving the entire frame up to crop out a microphone that’s inadvertently dropped into the shot.

Advantages of Grading with Color

When Does Color Correction Happen? discusses how color correction is accomplished in other post-production environments. This section describes how Color fits into a typical film or video post-production process.

Color provides many of the same high-end color correction tools on your desktop that were previously available only in high-end tape-to-tape and telecine color correction suites. In addition, Color provides additional tools in the Color FX room that are more commonly found in dedicated compositing applications, which give you even more detailed control over the images in your program. (For more information, see The Color FX Room.)

Color has been designed as a color correction environment for both film and video. It’s resolution-independent, supporting everything from standard definition video up to 2K and 4K film scans. It also supports multiple media formats and is compatible with image data using a variety of image sequence formats and QuickTime codecs.

Color also has been designed to be incorporated into a digital intermediate workflow. Digital intermediate refers to a high-quality digital version of your program that can be edited, color corrected, and otherwise digitally manipulated using computer hardware and software, instead of tape machines or optical printers.

Editors, effects artists, and colorists who finish video programs in a tapeless fashion have effectively been working with digital intermediates for years, but the term usually describes the process of scanning film frames digitally, for the purposes of doing all edit conforming, effects, and color correction digitally. It is then the digital image data which is printed directly to film or compiled as a file for digital projection.

Finishing film or video programs digitally frees colorists from the limitations of film and tape transport mechanisms, speeding their work by letting them navigate through a project as quickly as they can in a nonlinear editing application. Furthermore, working with the digital image data provides a margin of safety, by eliminating the risk of scratching the negative or damaging the source tapes.

When Does Color Correction in Color Happen?

Color correction using Color usually happens at or near the conclusion of the online edit or project conform, often at the same time the final audio mix is being performed. Waiting until the picture is locked is always a good idea, but it’s not essential, as Color provides tools for synchronizing projects that are still being edited via XML files or EDLs.

Color has been designed to work hand in hand with editing applications like Final Cut Pro; Final Cut Pro takes care of input, editing, and output, and Color allows you to focus on color correction and related effects.

About Importing Projects and Media into Color

To work on a program in Color, you must be provided with two sets of files:

  • Final Cut Pro sequence data can be sent to Color directly using the Send To Color command. Otherwise, the edited project file (or files, if the program is in multiple reels) should be provided in a format that can be imported into Color. Compatible formats include Final Cut Pro XML files, and compatible EDL files from nearly any editing environment.

  • High-quality digital versions of the original source media, in a compatible QuickTime or image sequence format.

Project and media format flexibility means that Color can be incorporated into a wide variety of post-production workflows. For an overview of different color correction workflows using Color, see Color Correction Workflows.

About Exporting Projects from Color

Color doesn’t handle video capture or output to tape on its own. Once you finish color correcting your project in Color, you render every shot in the project to disk as an alternate set of color-corrected media files, and you then send your Color project back to Final Cut Pro, or hand it off to another facility for tape layoff or film out. For more information, see The Render Queue.

What Footage Does Color Work With?

Color can work with film using scanned DPX or Cineon image sequences, or with video clips using QuickTime files, at a variety of resolutions and compression ratios. This means you have the option of importing and outputting nearly any professional format, from highly compressed standard definition QuickTime DV-25 shots up through uncompressed 2K or 4K DPX image sequences—whatever your clients provide.