With all the buzz about various digital cameras like RED and the latest HDSLRs, it’s easy to forget that most national commercial campaigns, dramatic television shows, feature films and many local and regional spots are still filmed with ACTUAL 16mm and 35mm motion picture film. As an editor, you need to have a good understanding about the film transfer workflow and what information needs to be communicated between an editor and the transfer facility or lab.
Film transfers and speed
Film is typically exposed in the camera at a true 24fps. This is transferred in real-time to video using a scanner or telecine device like a Cintel Ursa or a DFT Spirit. During this process, the film’s running speed is slowed by 1/1000th to 23.98fps (also expressed as 23.976) – a rate compatible with the 29.97fps video rate of the NTSC signal. In addition, film that is being transferred to NTSC (525i) or high definition video for television (1080i/29.97 or 720p/59.94) is played with a cadence of repeated film frames, know as 3-2 pulldown. Film frames are repeated in a 2-3-2-3 pattern of video fields, so that 24 film frames equals 30 interlaced video frames (or 60 whole frames in the case of 720p) within one second of time. (Note: This is specific to the US and other NTSC-based countries. Many PAL countries shoot and post film content targeted for TV at a true 25fps.)
Film production requires the use of an external sound recorder. This production method is known as double-system sound recording. Analog audio recorders for film, like a Nagra, record at a true sound speed synced to 60Hz, or if timecode was used, at a true timecode value of 30fps. When the audio tape is synced to the film during the film-to-tape transfer session, the audio goes through a similar .999 speed adjustment, resulting in the sound (and timecode) running at 29.97fps instead of 30fps as compared to a real-time clock.
The film sound industry has largely transitioned from analog recorders – through DATs – to current file-based location recorders, like the Aaton Cantar or the Zaxcom Deva, which record multichannel Broadcast WAVE files. Sound speed and the subsequent sync-to-picture is based on sample rates. One frequent approach is for the location sound mixer to record the files at 48048 kHz, which are then “slowed” when adjusted to 48kHz inside the NLE or during film-to-tape transfer.
The objective of a film-to-tape transfer session is to color-correct the image, sync the sound and provide a tape and metadata for the editor. Sessions are typically booked as “unsupervised” (no client or DP looking over the colorist’s shoulders) or “supervised” (you are there to call the shots). The latter costs more and always takes more time. Unsupervised sessions are generally considered to be “one-light” or “best-light” color correction sessions. In a true one-light session, the telecine is set-up to a standard reference film loop and your footage is transferred without adjustment, based on that reference. During a best-light session, the colorist will do general, subjective color-correction to each scene based on his eye and input from the DP.
Truthfully, most one-light sessions today are closer to a best-light session than a true one-light. Few colorists are going to let something that looks awful go through, even if it matches a reference set-up. The best procedure is for the DP to film a few seconds of a Macbeth and a Grayscale chart as part of each new lighting set-up, which can be used by the colorist as a color-correction starting point. This provides the colorist with an objective reference relative to the actual lighting and exposure of that scene as intended by the DP.
Most labs will prep film negative for transfer by adding a countdown leader to a camera roll or lab roll (several camera rolls spliced together). They may also punch a hole in the leader (usually on the “picture start” frame or in the first slate). During transfer, it is common for the colorist to start each camera roll with a new timecode hour. The :00 rollover of that hour typically coincides with this hole punch. The average 35mm camera roll constitutes about 10-11 minutes of footage, so an hour-long video tape film transfer master will contain about five full camera rolls. The timecode would ascend from 1:00:00:00 up through 5:00:00:00 – a new hour value starting each new camera roll. A sync reference, like a hole-punched frame, corresponds to each new hour value at the :00 rollover. The second videotape reel would start with 6:00:00:00 and so on.
Many transfer sessions will also include the simultaneously syncing of the double-system audio. This depends on how the sound was recorded (Nagra, DAT or digital file) and the gear available at the facility. Bear in mind that when sound has to be manually synced by the colorist for each take – especially if this is by manually matching a slate with an audible clap – then the film-to-tape transfer session is going to take longer. As a rule-of-thumb MOS (picture-only), one-light transfer sessions take about 1.5 to 2 times the running length of the footage. That’s because the colorist can do a basic set-up and let a 10 minute camera roll transfer to tape without the need to stop and make adjustments or sync audio. Adding sound syncing and client supervision, often means the length of the session will increase by a factor of 4x or 5x.
The procedure for transferring film-to-tape is a little different for features versus a television commercial or a show. When film is transferred for a feature film, it is critical that a lot of metadata be included to facilitate the needs of a DI or cutting negative at the end of the line. I won’t go into that here, because it tends to be very specialized, but the information tracked includes audio and picture roll numbers, timecode, film keycode and scene/take information. This data is stored in a telecine log known as a FLEX file. This is a tab delimited text file, which is loaded by the editor into a database used by the NLE. It becomes the basis for ingesting footage and is used later as a cross-reference to create various film lists for negative cutting from the edited sequences.
If your use of film is for a commercial or TV show, then it’s less critical to track as much metadata. TV shows generally rely on tape-to-tape (or inside the NLE) color-correction and will almost never return to the film negative. You still want to “protect” for a negative cut, however, so you still need to track the film information. It’s nice to have the metadata as a way to go back to the film if you had to. Plus, some distributors still require cut negative or at least the film lists.
It’s more important that the film be transferred with a set-up that lends itself to proper color grading in post. This means that the initial transfer is going to look a bit flatter without any clipped highlights or crushed blacks. Since each show has its own unique workflow, it is important that the editors, post supervisor and dailies colorists are all on the same page. For instance, they might not want each camera roll to start with a new hour code. Instead, they might prefer to have each videotape reel stick with consistent ascending timecode. In other words, one hour TC value per videotape reel, so you know that 6:00:00:00 is going to be the start of videotape reel 6, and not film camera reel 6 / videotape reel 2, as in my earlier example.
Communication and guidelines are essential. It’s worth noting that the introduction of Digital Intermediate Mastering (DI) for feature films has clouded the waters. Many DI workflows no longer rely on keycode as a negative cut would. Instead, they have adopted a workflow not unlike the spot world, which I describe in the next section. Be sure to nail down the requirements before you start. Cover all the bases, even if there are steps that everyone assumes won’t be used. In the end, that may become a real lifesaver!
The spot world
I’m going to concentrate of the commercial spot world, since many of the readers are more likely to work here than in the rarified world of films and film-originated TV shows. Despite the advances of nonlinear color grading, most ad agencies still prefer to retransfer from the film negative when finishing the commercial.
This is the typical workflow:
- Transfer a one-light to a video format for offline editing, like DVCAM
- Offline edit with your NLE of choice
- Generate transfer lists for the colorist based on the approved cut
- Retransfer (supervised correction) selects to Digibeta or HD for finishing
- Online editing/finishing plus effects
In this world, often different labs and transfer facilities, as well as editorial shops, may be used for each of these steps. Communication is critical. In many cases the director and DP may not be involved in the transfer and editing stages of the project, so the offline editor frequently plays the role of a producer. This is how spot editors worked in the film days and how many of the top commercial cutters still work today in New York, LA, Chicago or London.
In the first two steps, the objective is to get all of the footage that was shot ready to edit in the least time-consuming and most inexpensive manner possible. No time wasted in color-correction or using more expensive tape formats just to make creative decisions. The downside to this approach is that the client sometimes sees an image that isn’t as good as it could be (and will be in the end). This means the editor might have to do some explaining or add some temporary color-correction filters, just so the client understands the potential.
When the offline editing is done, the editor must get the correct info to the colorist who will handle the retransfer of the negative. For example, if each camera roll used a different hour digit, it will be important for the editor to know – and to relay – the correct relationship between camera rolls and timecode starts. For instance, if a hole punch was not used, then does 1:00:00:00 match “picture start” on the camera one leader? Does it match the 2-pop on the countdown? Does it match the first frame of the slate?
When film negative is retransferred, the colorist will transfer only the shots used in the finished cut of the commercial. Standard procedure is to transfer the complete shot “flash-to-flash”. In other words, from the start to the end of exposure on that shot. If it’s too long – as in an extended recording with many takes – then the colorist will transfer the shot as cut into the spot, plus several seconds of “handles”. This is almost always a client-supervised session and it can easily take 6-8 hours to work through the 40-50 shots that make up a fast paced spot.
The reason it’s important to know how the timecode corresponds to the original transfer, is because the colorist will use these same values in the retransfer. The colorist will line up camera roll one to a start frame that matches 1:00:00:00. If a shot starts at 1:05:10:00, then the colorist will roll down to that point, color-correct the shot and record it to tape with the extra handle length. Colorists will work in the ascending scene order of the source camera rolls – not is the order that these shots occur in the edited sequence. This is done so that film negative rolls are shuttled back and forth as little as possible.
As shots are recorded to videotape, matching source timecode will be recorded to the video master. As a result, the videotape transfer master will have ascending timecode values, but the timecode will not be contiguous. The numbers will jump between shots. During the online editing (finishing) session, the new footage will be batch-captured according to the shots in the edited sequence, so it’s critical that the retransferred shots match the original dailies as frame-accurately as possible. Otherwise the editor would be forced to match each shot visually! Therefore, it’s important to have a sufficient amount of footage before and after the selected portion of the shot, so that the VTR can successfully cue, preroll and be ingested. If all these steps are followed to the letter, then the online edit (or the “uprez” process) will be frame-accurate compared with the approved rough cut of the spot.
To make sure this happens smoothly, you need to give the colorist a “C-mode” list. This is an edit decision list that is sorted in the ascending timecode order of the source clips. This sort order should correspond to the same ascending order of shots as they occur on the camera rolls. Generating a proper C-mode EDL in some NLEs can be problematic, based on how they compute the information. Final Cut is especially poor at this. A better approach is to generate a log-style batch list. The colorist doesn’t use these files in an electronic fashion anyway, so it doesn’t matter if it’s an EDL, a spreadsheet, a hand-written log or a PDF. One tactic I take in FCP is to duplicate the sequence and strip out all effects, titles and audio from the dupe. Next, I copy & paste the duped sequence to a new, blank bin, which creates a set of corresponding subclips. This can be sorted and exported as a batch list. The batch list, in turn can be further manipulated. You may add color correction instructions, reference thumbnail images and so on.
Once I get the tape back from the retransfer session, I will Media Manage (FCP) or Decompresss (Avid) the sequence to create a new offline sequence. These clips can then be batch-captured for the final sequence with full-quality video (also called “uprezzing”). In some cases, FCP’s Media Manager has let me down and I’ve had to resort to exporting an EDL and using that as a basis for the batch capture. EDLs have proven to be pretty bullet-proof in the spot world.
Even though digital is where it’s at – or so I’ve heard – film will be here for years. So don’t forget how to work with it. If you’ve never had to work with it yet, no time like the present to learn. Your day will come soon.
©2009 Oliver Peters