last updated 15 Feb 2009

DI - Conforming

Digital Intermediates - Conforming the scanned negative

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In the DI process, before one can grade or colour correct the film
one has to rebuild the edit so it correctly matches the editor's cut.
This is conforming. Its done after scanning the film.

Conforming is the electronic equivalent of negative cutting.

In case you've come here directly, check out my
DI basics and
DI scanning pages



Before starting the DI...

There could be as many as five to seven hundred rolls of 35 mm film negative film used to shoot an Indian feature film. After shooting, these film rolls are processed in a lab. And you have a film negative.

This negative consisting of hundreds of rolls of film needs to be edited. And for that they have to be telecined. Meaning converted to video.

While this telecine is being done, the telecine machine "reads" the "keycode" printed at the side of the film (between the sprocket holes) and makes out a table of keycodes vs. timecode. This is saved as a "log file" so the editing system can keep a track of keycodes which we're going to need later. 

More details on the preparatory work needed before DI on my DI - preparation page.



In India, wehich uses the PAL TV system, film is run at 25fps in the telecine, and transferred to tape at 25fps. 

This 24-25 fps stuff is for film editing in a PAL world. Most books and web sites refer to 30 fps and 29.97 fps. They are referring to NTSC.
In India we use PAL so I will only talk about editing 24 fps film in a 25 fps PAL world.

If you need to know how this works in NTSC then there many resources available on the net.


Putting the film together

The processed film is first "telecine'd" to video on Betacam or DV tapes. These tapes are captured into an Avid Film Composer or a Final Cut Pro system. The sound is also similarly transferred - it may be on DAT tapes or Nagra spools or files in hard disk recorders.

In either film edit system (Avid or FCP), picture and sound are cut together in a creative way and the film story is assembled. This is film editing. You could say this is the second time the film is "directed".

But this edit is an "offline edit". Meaning it is at video resolution. So this edit cannot be shown in theatres. So we need to somehow make a film edit that can be printed on a film and shown by a film projector in theatres for people to see.

So, after the offline edit is done, an EDL (edit decision list), cut list, and pull list are made. These are human readable lists of numbers in a tabular format. They describe the edit numerically. So that some other machine can accurately recreate the edit.

After the edit, comes an intermediate stage before the final print of the film is made. Conventionally this intermediate stage was done manually and optically. Since about 2001, computers and storage reached that point in their evolution where it became possible to do this "intermediate" process "digitally". Hence, "digital intermediates" which is the point of this whole web page.

So basically, Digital Intermediate or DI, replaces the negative cutting and grading-at-the-lab stages. All the rest of the film-making remains the same.




This is a fast forward explanation for a non-trivial occupation called feature film editing. A form of mediation that permits one to deny hunger and sleep.



Now we come to the next process of conforming the scanned film to the original edit. Sort of like electronic negative cutting. 

The offline edit as described above, results in lists like EDLs and cut lists that describe the entire edit as numbers showing from which timecode/keycode each shot is takes and placed in what order.

These EDLs are scanned by a scanner or datacine machine. (More on scanning on my DI-Scanning page)

So then, after all shots are scanned, they lie on a rather large hard disk. Then a "conform" system conforms them. By the numbers and by referring to the EDL or cut list.

What it does is reads EDLs or cut lists from the offline edit, and looks for the necessary shots on the hard disk, and then builds a timeline. Just like doing a normal "online" or upgrade.

After conform, you have your whole film in the form of a timeline at full film resolution - 2k. This is your "digital negative". And the whole conform process could be thought of as a "electronic negative cutting".

All through the grading process, it is necessary to ensure this "digital negative" is in sync with the original edit. And to enable this, most conform systems can do side by side comparisons on the same screen of the "digital negative" and the offline edit.

The process of conform just makes pointers to the actual media. It does not actually move of add or delete any files. Just like conventional non-linear editing. Except that one is working with full film resolution files.

And finally this conformed edit is used in the grading system to grade the film on a shot by shot and scene by scene basis. Looks are imparted to heighten the story, corrections made to the shoot if needed, clean-ups done, CGI Visual effects integrated. All this after conform and in the next process called "grading". More on grading on my DI-grading page.



Most DI systems manufacturers trivialize the conform process. Because their system cannot do it cleanly and with "zero" errors.

Make no mistake about this. No matter how well your film is graded it still has to be an exact clone of the offline. And this is something you find out when you make a married print. If the conform system is not "zero error" the sound will not be in sync.

Then try explaining to the producer about who pays for the print.

Conforming systems

The various commercially available and monumentally expensive systems that just do the simple job of conforming the scanned film into a timeline that's a clone of the offline edit.

Descriptions of these systems are to follow. Till then, I've linked to the original manufacturer's pages. Which open in new windows.

Note that some of these are actually grading systems that can also conform.


Some of the links to equipment below may be changed by the manufacturer. In that case, please Google the name and you'll find it.

Else, feel free to write to me here...

These are in no particular order.

Nucoda Film Cutter
Nucoda Film Master
Autodesk Lustre Assist    
Filmlight Baselight    
Quantel iQ    
daVinci Resolve    
Assimilate Scratch    
Iridas SpeedGrade    
Apple Color    
Thomson Bones    
Autodesk smoke and fire    
DVS Clipster    





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