Recently, large-screen televisions over 55-inch have been widely popularized. Display manufacturers need to know which luminance has great preference, familiarity, less fatigue and low power consumption for large-screen TVs. Most of earlier studies had focused on the proper luminance of TVs by considering a screen illuminance, visual angle and average picture level. On the other hand, it has been assumed that an amount of light and an average luminance on field of view of displays influence on a proper luminance. It has been focused on the perceptually equivalent luminance in large-screen TVs compared with current 55-inch TVs as mainstream. A physical measurement about amount of light and a subjective evaluation to examine the relationship of the perceptually equivalent luminance between a 55-inch display and large-screen displays have been conducted. The evaluation results show that average luminance on field of view is a major factor to influence the perceptually equivalent luminance. And it obtained the perceptually equivalent luminance of large-screen TVs is relatively low.