Colorimetric characterization of input media in motion picture production Steffen Paul The Norwegian Color Research Laboratory Faculty of Computer Science and Media Technology Gjøvik University College, Gjøvik, Norway Presentation of master project, Gjøvik, and

Introduction/Background Significant changes in the movie production work flow transition to digital technology Post production dominated by digital technologies advanced color grading digital effects But, preferred input medium is still analog film dynamic range larger gamut

lab Movie production work flow film set preview film- camera Keyframe Onset OCN (original camera negative) telecineediting, postpro

Movie production work flow Keyframe OnSet developed at Gjøvik University College in cooperation with Drylab R&D Oslo initial color grading on the set reports (Images) are send to the lab serve as reference for the telecine operator

Goal Simulate characteristics of film stock to images captured with a digital camera Limitations dynamic range different gamut sizes

Models XYZ RGB Film stock Digital camera forward transformation inverse transformation RGB

Models Indirect approach two models both devices are characterized seperatly maybe less precise, slower, but more flexible Direct approach one model for each possible combination of film stock/camera needed possibly more precise, faster, less flexible

Setup Test images provided by Drylab R&D Oslo film stock scanned (.dpx format) images from digital camera (RAW files)

ICC profiles Camera/scanner profiles (scnr) A2B tag no B2A tag (usually not needed) Printer/monitor profiles (prntr, mntr) A2B tag and B2A tag (softproofing) profiling software expects measurement data to be in XYZ (not RGB)

ICC profiles Inversed profile measurement data and reference data swopped it works, but..

Regression Indirect transformation determine the relationship between RGBcam, XYZref and RGBfilm values Direct transformation relationship between RGBcam and RGBfilm RGB values measured from test images spectral data converted to XYZ values for each test target models created with regression module in ICC3D evaluation with trainigset and testset

Regression

Regression vs ICC profile Kodak 200TdeltaE76deltaE00 Regression (3rd)4,482,77 ICC profile7,995,53

Conclusion Project showed limited use of ICC profiles regression proved working Test images show some problems underexposure non-uniform exposure clipped colors in test set

Future work models for several types of popular film stock implementation in Keyframe OnSet

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