Reports from the Field

Using Bayer-filter sensors to digitise films at full RGB

Most scanners use Bayer-filter sensors because they allow to digitise films quickly at a reasonable quality. One downside is that there exist various algorithm to de-mosaic the image, which gives better or worse results depending on the image content, but usually scanners do not allow to switch algorithm. Another downside is that the image generated contains only a quarter of the red, half of the green and a quarter of the blue information. However it’s possible to obtain full RGB quality with a Bayer-filter sensor at half of its horizontal and vertical pixel resolution. Our experimental video encoder allows to achieve this transformation during the digitisation.

The openMovIm package, which we are currently testing in an alpha release, contains the following elements:

• MovIm is a video codec specifically designed for conservation and restoration purposes;
• libmovim is a C library implementing the MovIm video codec and movimdec, movimenc and movimplay its associated utilities;
• openmovim is a Bash command-line interface to encode, decode, play and analyse moving images.

We wish to present to our colleagues and friends some results of our wider research on colour filter array sensors, and to share with them our thoughts.

When and Where

A short talk by Reto Kromer, with demonstrations on both macOS and Windows running Ubuntu, followed by an informal Q&A session and light refreshments, on Friday the 24^th of May 2019, starting at 11 o’clock sharp, at AV Preservation by reto.ch in Écublens (a suburb of Lausanne, Switzerland).

As usual, the admission is free, but an inscription by email is required, because only six places are available at our small facility. Note that this will be a technical meeting and the attendees should be familiar with high-school maths, including functions, linear transformations and elementary matrix operations.

2019-05-22