An Analysis of System Contrast in Digital Cinema Auditoriums

Abstract

High dynamic range for digital cinema projectors demands both increased brightness and darker black levels. Projector contrast is commonly described as the ratio of peak white luminance to black state luminance, where these extremes are measured sequentially. However, in a typical movie, bright highlights and deep blacks coexist in the same frame, introducing a number of other factors greatly affecting perceived dynamic range. This paper reports on the relative impact of such factors, including lens veiling glare, port glass, room reflectivity, audience reflectivity, and room ambient lighting. We will report on recent studies that have measured typical auditorium and lens parameters, as well as a representative luminance of recent movies, which greatly impacts the degree to which stray light is reflected back onto the screen. Based on these factors, the resulting “system contrast ratio” of typical cinema screenings is calculated.