Comparing ACES Input Device Transforms for the Canon EOS 5D Mark III DSLR camera

Abstract

Color is an important aspect of the camera quality. Above all in a Visual Effects Pipeline (VFX) it is necessary to maintain a linear relationship of the pixel color in the recorded image to the original light of the scene throughout every step in the production pipeline. This means that the plate recorded by the camera is not permitted to be subject of changes in any way (,,do no harm to the plate"). Unfortunately most of the camera vendors are applying certain functions during the input step to the recorded RAW material, mostly to meet the needs of the display devices at the end of the pipeline. But they also are adding functions to establish a certain look the camera company is associated with. Maintaining a linear relationship to the light of the scene enables compositing artists and editors to combine imagery of varying sources (mostly cameras of different vendors). The Academy of Motion Picture Arts and Science (AMPAS) established an Academy Color Encoding System (ACES). To achieve a linear relationship to the light of the scene, Input Device Transforms (IDTs) for most of the digital film cameras have been provided recently. Unfortunately, such IDTs are not available for nearly all consumer and DSLR cameras. To add their imagery to the film production pipeline it is desirable to create convenient IDTs for such devices as well. The goal of this paper is to record the spectral distribution of a GreagMacbeth ColorChecker using a spectrometer and also photography it with a Canon EOS 5D Mark III camera under the same lighting conditions. The RAW image is then converted to ACES color spacers (ACES2065-1 or ACEScg) using industrial approved RAW converters. The positions of the patches of the ColorChecker in CIEYxy color space are then compared to the positions of the patches captured by the spectral device. As a result a tendency could be obtained if the camera can be used inside the AMPAS ACES workflow.