White PaperImproving Visibility in Dark Areas with Smart Insight

CONTENTS
1． INTRODUCTION ............................................................................................................................................................................22． TECHNOLOGY TO IMPROVE VISIBILITY IN DARK AREAS..................................................................................................32-1．CONVENTIONAL TECHNOLOGY TO IMPROVE VISIBILITY IN DARK AREAS .........................................................................................32-2．POWERGAMMA ...........................................................................................................................................................................33．SMART INSIGHT TECHNOLOGY ..................................................................................................................................................43-1．VISUAL DIFFERENCES BETWEEN REAL OBJECTS AND MONITOR IMAGES ..........................................................................................43-2．VISUAL REPRODUCTION USING THE HUMAN EYE ...........................................................................................................................53-3．IMPROVING VISIBILITY IN DARK AREAS WITH SMART INSIGHT .......................................................................................................6
3-4．EFFECT OF SMART INSIGHT ..........................................................................................................................................................74．SUMMARY........................................................................................................................................................................................8No.12-001 Revision AJuly 2012
EIZO NANAO CORPORATION

Improving visibility in dark areas with Smart Insight

1． Introduction
We have been striving to create high quality image technology such as high precision gamma correction,brightness stability control and digital uniformity equalizer technology, aiming for "monitor display that isfaithful to the original image source".
We have implemented this concept of high quality image technology into FORIS, our line of homeentertainment monitors. Thus, we have developed FORIS based on the concept of "natural comfort", in whichmonitors express the color tone and smoothness of an image source accurately and naturally.
However, while "natural comfort" is certainly an essential concept to accurately reproducing the intention ofimage creators, depending on diverse user environments and preferences as well as image source, accurate
reproduction of the image source itself does not necessarily result in user satisfaction. When viewing low tones
and dark areas, on the monitor visibility changes significantly in response to the environment in which it isviewed (surrounding luminance) and monitor brightness. Therefore, the concept of natural comfort could makeareas we want to see, harder to view.
To solve this problem, we developed Smart Insight, which improves visibility in dark areas and suits userpreferences (details described in this document.) This function improves visibility in dark areas while retaining
the original texture of the image source and provides visibility that emulates how things appear in the realworld. In addition, Smart Insight includes the concept of “natural comfort” and provides newly added value
based on the concept, “make the scene come alive” which means to accurately reproduce real-world images onthe monitor.

FORIS FS2333 monitor equipped with Smart InsightPage 2

Improving visibility in dark areas with Smart Insight

2． Technology to improve visibility in dark areas
2-1．Conventional technology to improve visibility in dark areas
Conventional monitors apply gamma correction across the screen as a means of improving visibility in low
tone areas. The essential purpose of gamma correction is to linearize optical input-output relation by adjustinggamma value in response to the input image source. Since gamma correction allows the output value of low
tone areas to rise, users can use gamma correction to brighten those areas.
However, using gamma correction to improve visibility in dark areas can brighten light areas excessively andresult in a loss of tonality.

2-2．PowerGamma
We developed the FORIS FS2331 in November 2010 which provides Power1 and Power2 gamma correction
settings to improve visibility in dark areas of game images. In particular, Power2 enhances visibility in darkareas without sacrificing tone display.
However, since gamma correction applies tone conversions to all tones equally, the local contrast of outlines
and textures may decrease. This can cause gamma correction to create an impression differing from the textureof the original image. Also, as gamma correction is not suitable for some kinds of images, we provide thePowerGamma setting for games only.

FORIS FS2331 monitor equipped with PowerGamma

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Improving visibility in dark areas with Smart Insight

3．Smart Insight Technology
Smart Insight extracts local contrast information of an image from each pixel and corrects and brightens theimage while preserving the original texture. In addition, Smart Insight detects the overall brightness of thewhole image and the tone bias within the frame, and then adjusts the parameters in response to the scenes
automatically. This section describes the visual differences between original, real images and those producedby conventional monitors, as well as the reasoning behind the development of Smart Insight.

3-1．Visual differences between real-life and monitor images
When we photograph subjects with a significant difference between backlighting and shadow, images shownon the monitor could sometimes be dark and hardly visible. We can prevent this type of phenomenon to someextent by adjusting the exposure on the camera. However, exposure adjustment usually applies to the whole
screen so lengthening exposure time may cause the saturation of bright areas, making the images hardlyvisible.

Original image with a camera

Image corrected by Smart Insight

The shadow of the table looks darker

The shadow of table is close to its actual

than its actual color.

color.

The reason for such low visibility in the dark area is because the brightness of the monitor output issignificantly darker than real-life. For example, the luminance in mid-summer is approximately 100,000 lx inthe sun and 10,000 lx in the shade. However, the maximum luminance of general monitors is several hundred
cd/m² and the minimum is close to zero. Although the units between the luminescent and illuminated sides
differ, the brightness of what we see is significantly different between the monitor and the real thing. In short,the monitor can brighten the low tone areas (a few cd/m² on the screen) in the photograph of a subject that is
10,000 lx luminance in the shade.
The human eye optimizes a dynamic range of brightness perception by adapting to the brightness of its
surroundings. However, eyes have to acclimate to a dark environment to recognize a few cd/m² of luminance.
We can not easily adapt to a dark environment each time when looking at an image on the monitor. Therefore,
it is harder to see the dark areas of the picture compared to what we see in real-life.

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Improving visibility in dark areas with Smart Insight3-2．Visual reproduction using the human eye
A monitor’s luminance range is lower than in the real world so the monitor can not reproduce a perfect opticalrepresentation of a real subject. However, the perception of the human eye adapted to its surrounding
brightness (dynamic range of perception) is said to be at about an order of 10^2 (approximately 100:1 –1000:1). Although the optical absolute value is inaccurate, with perception representation, the dynamic range(approximately 400:1 – 1000:1) of a monitor can reproduce visibility that emulates the real subject.
The images below describe an optical illusion. Although the gray square on the right looks darker than the left,
both squares have same level of brightness. This optical illusion is mainly caused by the cone cells,
photoreceptor cells which identify color and brightness with photopic vision; concentrating near the center ofthe eye’s viewpoint. This is known as “lightness constancy.”

Both gray squares have the same level of brightness.
This optical illusion indicates that brightness and color that humans perceive, depends on the relative change
between their surroundings rather than absolute optical representation within the image. The Retinex theory
expresses this phenomenon through a physical model. We developed Smart Insight on the basis of this theory.
The Retinex theory describes the intensity of the light that enters the eye I as a product of the reflectance of anobject R and light L as shown in the following formula.
I=RxL
From the view of image processing, the Retinex theory is simply expressed as “the perception of the brightness
and color of pixels is more influenced by the relative change between the surrounding area and the point ofobservation over the absolute values of the optics.” The relative optical amount here is the reflectance R fromthe above formula, and corresponds to the detail of the image outline component i.e. the local contrast
component.
Thus, to improve the visibility in low tone areas of a monitor using the Retinex theory, the monitor needs toextract reflectance components from an input image R, and then adjust the light component L. Then, it
becomes possible for the monitor to implement visibility emulating real-world values.

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Improving visibility in dark areas with Smart Insight

3-3．Improving visibility in dark areas with Smart Insight
The figures below describe the image correction process with Smart Insight.
・ First, our original process separates the input image’s illumination component and reflectance component.
Then, Smart Insight calculates the value of the illumination component and the reflectance component byanalyzing the local image area centering on a certain pixel as shown outlined in the red square below.
・ Next, it corrects the brightness of the dark areas of the illumination component and recombines itwith thereflectance component.
・ Now Smart Insight has produced the image with the correct brightness while retaining local contrast.

Separating input image

Correcting brightness

Illumination component

Separating input image

Retaining original values

Reflectance component
Through these measures, Smart Insight brightens low tone areas and converts the image to an accurate
representation of the real subject. Moreover, Smart Insight corrects the dark areas of the illumination
component, as well as overall screen brightness and tone bias with our original dynamic control. The amountof correction is dependant on illumination. For example, Smart Insight actively corrects dark scenes andcarefully corrects bright scenes. Therefore, we can always see various moving images with the appropriate
amount of correction.

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Improving visibility in dark areas with Smart Insight

3-4．Effect of Smart Insight
The figures below show the differences between correction by conventional gamma and Smart Insight.

Original image

Image corrected by Smart InsightPage 7

Improving visibility in dark areas with Smart InsightGamma correction γ=1.6
Gamma correction can improve visibility of the dark area, however, since gamma correction converts all tones
equally, local contrast decreases and outlines becomes blurred. Also, the entire image becomes whitish fromthe loss of vividness.
Smart Insight corrects the brightness in dark details while retaining the original local contrast and details, likethe outline, remain clear. Moreover, Smart Insight corrects only illumination while retaining hue and saturation
so images don’t fade in color and the corrected areas appear more vivid. This phenomenon is caused by theHunt effect, a visual trait where vibrancy increases with luminance.

4．Summary
Our new Smart Insight technology improves visibility in dark areas while retaining visual naturalness. This
technology provides not only visual improvement but also brightness adjustment in response to contents oruser preferences without increasing the light volume of backlights allowing for lower power consumption.
Moreover, since the delay of this process is only a few lines, Smart Insight is ideal for games which requirereal-time responsiveness as well as watching movies, pictures and more.

Copyright © 2012 EIZO NANAO CORPORATION. All rights reserved.

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