Abstract

Many challenges that deal with processing of HDR material remain very much open for the film industry, whose extremely demanding quality standards are not met by existing automatic methods. Therefore, when dealing with HDR content, substantial work by very skilled technicians has to be carried out at every step of the movie production chain. Based on recent findings and models from vision science, we propose in this work effective tone mapping and inverse tone mapping algorithms for production, post-production and exhibition. These methods are automatic and real-time, and they have been both fine-tuned and validated by cinema professionals, with psychophysical tests demonstrating that the proposed algorithms outperform both the academic and industrial state-of-the-art. We believe these methods bring the field closer to having fully automated solutions for important challenges for the cinema industry that are currently solved manually or sub-optimally. Another contribution of our research is to highlight the limitations of existing image quality metrics when applied to the tone mapping problem, as none of them, including two state-of-the-art deep learning metrics for image perception, are able to predict the preferences of the observers.

Highlights

  • High Dynamic Range (HDR) technology can provide a never before seen increase in contrast, colour and luminance

  • – The methods have very low computational complexity and can be executed in real-time. – We show the limitations of existing objective image quality metrics for TM and ITM, since they do not correlate well with the preferences of observers. – Our TM and ITM algorithms are based on vision models whose parameters are finetuned by cinema professionals

  • The other choice we make is that our goal is for T M to approximate V1, and have cinema experts optimize its parameters in a reference environment so that (1) holds: in other words, we propose as tone mapping operator a vision model that is fine-tuned by cinema professionals

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Summary

Introduction

High Dynamic Range (HDR) technology can provide a never before seen increase in contrast, colour and luminance. Multimedia Tools and Applications (2021) 80:2537–2563 subtle colour gradations, to perceive highlights as much brighter than diffuse white surfaces, all things that we associate with everyday experiences and that cannot be reproduced using SDR (Standard Dynamic Range) systems This allows filmmakers to overcome artistic limitations that have existed since the inception of cinema, giving them the “perceptual tools that fine artists working in the medium of painting have had for hundreds of years” [77] and that provide compelling new opportunities for storytelling. We are currently a long way from such an ecosystem, as stated in recent reports from several international organizations and standardization bodies [29, 70, 75] as well as very recent publications from the motion picture and TV community [9, 24, 58, 64, 66, 78] This is due to open challenges happening at all stages of the production chain, from capture to display. Though color grading may seem complex given the vast number of buttons, knobs and switches on the control surface, that is only the user interface: the underlying math that the software uses to transform the image is too primitive and simple to achieve the type of rich transformations [...] that define the core of the complex perceptual look” [87]

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