From C+T:

DoP Heads Up – From Production to Finish

Wolfgang Lempp, CEO and co-founder, FilmLight, reports.

Movies and high quality television programmes are now routinely shot with digital cameras, and completed with a range of extremely powerful post-production tools. One of the great benefits of the ability to handle file-based content on today’s powerful processors is that it has opened up the possibility of sophisticated, real-time post.

Our specialisation is in colour grading, and we see the practicalities of rendering images to present the look becoming ever more unnecessary. Today we advocate a metadata-driven workflow where images are rendered only at the point of delivery, allowing everyone in the post process to benefit from the latest grading decisions without delay. Alongside our flagship colour grading systems, we offer plugins for other popular post devices including Avid and NUKE, which allow their operators to see graded images at all times and even to tweak a grade if necessary without rendering.

The downside of the render-free workflow, however, is the temptation to simply ensure you have captured sufficient latitude in the camera, then, as the old saying has it, ‘fix it in post’. That is a real disadvantage, though, because the director of photography, with the director, is more comfortable knowing that what was shot is going to match the look of the film in their imagination.

Because of the way that high dynamic range digital cinematography cameras work, there has to be a translation between the raw image and the colour space the image is going to finally inhabit. So everyone accepts that there will be colour processing. The ideal solution, therefore, is for processing at the camera so that the viewfinder or monitor looks ‘right’, providing reassurance that the desired look has been captured.

That is the thinking behind a new, free Mac app from FilmLight called Prelight. It is a means to ensure that what the DoP sees becomes the foundation of the grade downstream. This is accomplished in two ways.

First, stills can be grabbed during test shoots, and the DoP can work with the project’s colourist to set the look, the colour balance and dynamic range for each scene. These looks – look-up tables (LUTs) to transform the raw camera output – are downloaded into Prelight and used to provide on-set monitoring.

Second, the system can also work in the opposite direction. Prelight can be used on set, with a simple grading interface, to create stills that convey the look the DoP is seeking.

Primarily, this is visual communication between the DoP and the post team; the DoP is thinking in terms of images, so it makes sense to talk to the post team in the same language. But these colour decisions will also be captured and can be transmitted as metadata along with the pictures. This is in FilmLight’s Baselight Linked Grade (BLG) format, which means that if the downstream processing uses Baselight then decisions made in Prelight form the foundation of the grade.

Naturally, there is an expectation of standardisation, that the on-set metadata should be visible to any downstream grading system. The ASC CDL format was an attempt at this, but in truth it is a limited set of instructions that puts too much of a brake on the colourist’s creativity.

Inevitably, developers of grading systems depend on their own unique internal tools and routines so it seems likely that there will always be proprietary metadata formats. But with Prelight, even if you go to another grading system, you have the visual references – the stills set up after the test shoot, and the stills created on set.
One perhaps unexpected benefit of Prelight is to minimise errors and reduce asset management tasks. It is important that the right look is associated with each shot, and in current workflows someone has to associate a LUT with the content.

With Prelight the intent is that you design the look in advance, perhaps adjust it on set as you visualise it on the camera, then stream the metadata with the video so the look is carried through to the edit suite. We are currently talking to camera vendors, and have worked extensively with ARRI, to allow Prelight metadata to be embedded straight into the data stream.

The Prelight approach could also be extended to camera matching. DoPs have their preferred cameras, and there is accepted wisdom on the strengths of each camera: the ALEXA is generally regarded as being particularly kind on skin tones, for example. But in truth, the very high dynamic range means that any of the popular top-end cameras can be set up, through LUTs, to deliver the look you need.

There may be times when you have to use a different camera for a shot. It might be that you need a smaller form factor for a tight location, or even that you need multiple cameras for a big scene and availability is limited. Prelight can be used to establish the LUTs for each camera to make them match, all tuned to the preferred look.

The fundamentals of this approach are all in place, and the intention is that the basic software will be free, running on a Mac laptop that you can simply plug straight into your existing workflow.

The challenge that remains is in ensuring a consistent viewing experience: if the colour space of the on-set monitor is significantly different to the viewing theatre where the look was set, then chances are the DoP is going to be disappointed.

This isn’t a new problem, however, and the colour science behind ensuring a consistent viewing experience is well known – we have been offering our Truelight system for over a decade now. In its latest incarnation, with Truelight Colour Spaces, it allows our systems to handle natively most colour management operations without LUTs or Truelight profiles. With a little forward planning, this approach can dramatically simplify most workflows as well as improve the viewing consistency.

We believe the result is a simple, logical and perfectly clear way to communicate feelings about an image, from set to finishing. Using primarily visual communication, backed up with technology, it puts control of the look firmly in the hands of the DoP.