40 research outputs found
The preferred system gamma is primarily determined by the ratio of dynamic range of the original scene and the displayed image
The dynamic range of real world scenes may vary from
around 102
to greater than 107
, whilst the dynamic range of monitors
may vary from 102
to 105
. In this paper, we investigate the
impact of the dynamic range ratio (DRratio) between the captured
scene and the displayed image, upon the value of system gamma
preferred by subjects (a simple global power law transformation
applied to the image). To do so, we present an image dataset
with a broad distribution of dynamic ranges upon various subranges
of a SIM2 monitor. The full dynamic range of the monitor
is 105 and we present images using either the full range, 75% or
50% of this, while maintaining a fixed mid-luminance level. We
find that the preferred system gamma is inversely correlated with
the DRratio and importantly, is one (linear) when the DRratio is
one. This strongly suggests that the visual system is optimized
for processing images only when the dynamic range is presented
correctly. The DRratio is not the only factor. By using 50% of
the monitor dynamic range and using either the lower, middle or
upper portion of the monitor, we show that increasing the overall
luminance level also increases the preferred system gamma,
although to a lesser extent than the DR ratio
Perceived dynamic range of HDR images
Although high dynamic range (HDR) imaging has gained great popularity and acceptance in both the scientific and commercial domains, the relationship between perceptually accurate, content-independent dynamic range and objective measures has not been fully explored. In this paper, a new methodology for perceived dynamic range evaluation of complex stimuli in HDR conditions is proposed. A subjective study with 20 participants was conducted and correlations between mean opinion scores (MOS) and three image features were analyzed. Strong Spearman correlations between MOS and objective DR measure and between MOS and image key were found. An exploratory analysis reveals that additional image characteristics should be considered when modeling perceptually-based dynamic range metrics. Finally, one of the outcomes of the study is the perceptually annotated HDR image dataset with MOS values, that can be used for HDR imaging algorithms and metric validation, content selection and analysis of aesthetic image attributes