(Red visual +Green visual + Blue visual) Lumensįigure 2. (Red visual or Green visual or Blue visual) Lumens (Red 100% or Green 100% or Blue 100%) Lumens *the 2.4x average perceived brightness ratio is determined by Viewsonic LED projectors, other LED projectors may have a different result **Perceived Brightness Ratio = Both ratios can be calculated by using the formulas below. The perceived brightness ratio is the difference between the perceived brightness with the measured brightness, while the average perceived brightness ratio is the difference with all of the colors combined. The y-axis shows the brightness comparison between the colors on the left and right column on Figure 1. The x-axis of this chart shows each individual RGB color compositing the light source on the LED projector. attempts to illustrate how the perceived brightness level varies color by color. (Simulated image to illustrate the HK effect)įigure 2. In addition, while the colored patches on the right may appear to have the same brightness as the center gray scale patches however, the ANSI Lumens brightness of the colored patches on the right is much lower than the center gray patches.įigure 1. Most observers would assume that the colored patches on the left are brighter than the gray scale patches in the center in actuality, they have the same measured ANSI Lumens brightness. To understand how this is possible, we must also understand that the human eye is more sensitive to certain wavelengths of light (Fig 1), and any projector with a light source that more closely matches the light response of the human eye will naturally have a higher perceived brightness.įigure 1 below helps to further illustrate the Helmholtz-Kohlrausch effect. Now imagine two projectors with the same measured ANSI Lumens brightness that appear to be at different brightness levels. This is mainly due to something called the HK (Helmholtz-Kohlrausch) effect, which causes observers to perceive images with higher color saturation to be brighter than the less saturated ones. ViewSonic follows industry standard ANSI methods to establish our projector brightness specifications, but ANSI brightness alone can’t always provide enough information to fully characterize the brightness performance of the latest generation of high-color gamut projectors with LED light sources. Understanding the Difference Between ANSI
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