Contrast Sensitivity Experiment to Determine the Bit Depth for Digital Cinema

TLDR

The SMPTE Color ad hoc group, formed in 2001, investigated colorimetric requirements for Digital Cinema Distribution Masters and issued a 2002 draft spec recommending XYZ color space, a gamma 1/2.6 transfer function, and 12 bits per color channel. Supported by Digital Cinema Initiatives, the authors designed a test to verify these color image encoding parameters. The contrast‑sensitivity experiment revealed that many observers could detect a one‑code‑value change with 10‑bit encoding, but few could with 12‑bit encoding, a result consistent with prior studies.

Abstract

The SMPTE Color ad hoc group was formed in 2001 (under DC28.2) to investigate the colorimetric requirements for the Digital Cinema Distribution Master (DCDM). A draft specification on color image encoding was published in September 2002 that recommended the use of XYZ color space, a gamma 1/2.6 transfer function, and 12 bits per color. With the support of Digital Cinema Initiatives (DCI), a test was designed to verify these color image encoding parameters. This paper reports the results of the contrast sensitivity experiment, which showed that many of our observers could see a modulation corresponding to a one code value change with 10-bit encoding, but few observers would see a one-code value change with 12-bit encoding. This result matches the results of published contrast sensitivity experiments.