Investigating the impact of image content and ambient light levels on preferred gamma

Adjusting the transfer function of a digital image by a gamma mapping is a simple yet robust way to adapt to viewing conditions. Previous studies have shown that source content, ambient light level and display brightness strongly impact the subjective preferred gamma. We present a study evaluating the impact of content and ambient light level factors simultaneously. A perception test in which 15 observers chose the preferred gamma for 27 pristine images at 3 ambient light levels (no light, low light - 5% of display peak white and average light - 34 % of display peak white) was carried out. Subjective results show that the main factors (image content and ambient light condition) are statistically significant and that the size of effect due to image content is larger than the variation due to level of ambient light. More participants and/or analyzes are necessary for a direct evaluation of the interaction between the two independent factors.