Film Recoding Process
Once all DI work has been completed the digital film frames will be sent to a digital film recorder. Each frame will be exposed in turn, building a new digitally mastered intermediate negative [or intermediate positive, although this is less common but may have the benefit of reducing the number of dupe processes undergone when striking the final print deliverable - at least until the speed of film recorders enables multiple internegative to be produced cost effectively for the direct production of projection prints].

Speed of film recording varies dependent on film recorder make & model as well as data format and associated processing such as sharpening. Expect 1 to 4 seconds per frame.

Film Recording Technology
There are two main technologies in use for film recorders - CRT and Laser - with some attempt at using LED/LCD displays too.

Much as with film scanner technology the real difference between film recorders is no longer the final image quality, as the two main technologies (CRT and Laser only - LED/LCD are not yet at the same quality level) are capable of equally high-quality final image outputs. The main deciding factor is really the requirements of the operation's business model, and accepting that the dynamic range attainable from the main film recorder manufacturers is equivalent at a full 2.0 density, with a similar MTF value, the final equipment decision has to be based on factors other than outright quality.

The above images show LaserGraphics Digital Film Recorders, and below the ArriLaser.

As a guide to the best system to use (CRT or Laser), experience at Light Illusion suggests that 'enhanced' digital capture systems - which is to say Sony CineAlta cameras which have electronic sharpening applied in-camera - benefit from the more 'organic' look of CRT film recorders, while film capture and Viper, which is a non-enhanced digital capture camera, benefit from the 'sharper' image produced via a Laser f recorder.

DPX or CIN?
One question when outputting digital film frames for film recording is the format to use.

Although DPX tends to be the standard for DI post-production these is a major danger with this format when recording out to film. The DPX format can be Linear or Log, specified by a ‘flag’ within the header of the image file. However, most film recorders don’t read this flag, and assume DPX to be linear! This can cause major issues with the film-out process.

If working Log, as one should, it is best to output Cineon .CIN files as these can only be Log, not Linear.

Controlling the Recording Process
As a guide to control of the film recording and processing stage, a selection of reference frames should be exposed at the head & tail of each and every output. These images should include the digital reference frames used to calibrate the DI grading monitor [see monitor set-up above] and any reference frames required by the film recorder used. This may include a 21 step grey scale sensiometric strip, but as a minimum must include at least one 445 and 470 LAD to enable Status M measurement of the negative [intermediate] and Status A measurement of the print to be made.

Status A checks should be made using the reference frames at each end of the output print (head/tail) to ensure accurate & stable film recording. If in any doubt measure the negative too. If the film recorder is not recording stable data the whole DI process is useless.

The main cause of film recorder instability tends to be temperature drift within the recorder's environment. And a density change of only 0.02 in status M (negative), which is very small in density terms, equates to 0.07 in status A (print) and is one printer light, which is very visible.

For more information on Film Recording see the ArriLaser or LaserGraphics websites.