How to Fix Low LCD Brightness: Causes and Practical Solutions

In industrial, medical, and outdoor equipment, insufficient LCD brightness is one of the most common—and most critical—pain points. Low brightness does not just affect visual comfort; under direct sunlight, the screen may become completely unreadable, rendering the device ineffective.

So why do LCDs often suffer from brightness limitations, and how can brightness be effectively improved? This article breaks it down clearly from an engineering perspective.

1. Common Causes of Insufficient LCD Brightness

Brightness issues usually stem from several core factors rather than a single cause.

1.1 Low Backlight Luminance (Typical Indoor Panels)

The backlight is the primary light source of an LCD.

• Typical standard backlight: 250–400 nits

• Outdoor or high-brightness requirements: 600–2000+ nits

An underpowered backlight is by far the most common reason for poor brightness.

1.2 Low Polarizer Transmittance

An LCD uses both upper and lower polarizers. If their transmittance is low, overall brightness drops significantly.

1.3 Inefficient Optical Films (Diffuser / Prism Films)

High-quality optical films improve light utilization efficiency. Inferior films cause substantial light loss within the backlight stack.

1.4 Suboptimal Bonding Structure

Air gaps in framed bonding structures introduce refractive index changes, reducing effective luminance.

1.5 Unoptimized Display Driving Parameters

Improper driver IC settings, PWM dimming parameters, or gamma curves can artificially limit achievable brightness.

1.6 Environmental Factors That Reduce Perceived Brightness

Examples include:

• Direct sunlight

• Highly reflective cover glass

• Display area partially blocked by housing or bezel

In these cases, the panel brightness itself may be adequate, but visibility is still compromised.

2. How to Increase LCD Brightness: 6 Proven Engineering Approaches

The following methods are widely used in the industry, each with its own trade-offs.

Solution 1: Increase Backlight LED Brightness (Most Direct)

The most effective and commonly used approach:

• Increase LED quantity

• Increase LED driving current

• Use higher-efficiency or dual-chip LEDs

✔ Advantages

• Significant brightness improvement

• Essential for outdoor and high-brightness displays

✘ Limitations

• Higher power consumption

• Increased thermal load

• Backlight redesign often required

Solution 2: Use High-Transmittance Polarizers

Polarizer transmittance typically ranges from 35% to 44% depending on grade.

✔ Advantages

• Improves brightness without increasing power

• Enhances overall clarity

✘ Limitations

• Requires polarizer replacement process

• Higher material cost

Solution 3: Add Brightness Enhancement Films (BEF / DBEF)

BEF (Brightness Enhancement Film)

• Uses prism structures to concentrate light

• Typically increases brightness by 30–60%

DBEF (Dual Brightness Enhancement Film)

• Recycles polarized light through reflection

• Brightness gain can reach 70–100%

• Particularly suitable for high-brightness designs

✔ Advantages

• No increase in power consumption

• One of the most cost-effective brightness enhancement methods

• Immediate and visible improvement

✘ Limitations

• Higher material cost

• Sensitive supply chain

• Strict assembly requirements (orientation and angle critical)

Solution 4: Upgrade Optical Stack (Diffuser & Reflector Films)

Using higher-quality diffuser and reflector films reduces internal light loss and improves output efficiency.

✔ Advantages

• Relatively low cost

• Improves luminance uniformity

✘ Limitations

• Limited brightness gain

• Requires backlight stack-up adjustment

Solution 5: Apply Full Optical Bonding (OCA / OCR)

Compared with framed bonding, full bonding eliminates the air gap and associated light loss.

✔ Advantages

• Brightness improvement of approximately 5–10%

• Higher contrast

• Better sunlight readability

• Reduced surface reflection

✘ Limitations

• Higher process complexity

• Increased manufacturing cost

Solution 6: Software-Level Optimization (Driver / Gamma / PWM)

Applicable when brightness is limited by configuration rather than hardware.

• Increase driver IC brightness parameters

• Optimize PWM duty cycle

• Adjust gamma curves

✔ Advantages

• No additional hardware cost

• Fast implementation

✘ Limitations

• Limited improvement

• Cannot exceed hardware capability

3. What If Outdoor Display Brightness Is Still Insufficient?

Outdoor environments combine two major challenges: direct sunlight and strong reflections.

A recommended combined solution includes:

• 1200–2000 nits high-brightness backlight

• DBEF dual brightness enhancement films

• Full optical bonding

• AR / AG / AF surface treatments

This combination ensures reliable readability even under harsh outdoor lighting conditions.

4. Summary

Insufficient LCD brightness is not caused by a single factor. It is the combined result of backlight capability, optical materials, structural design, bonding method, and driving parameters.

Effective brightness enhancement typically involves one or more of the following:

• High-brightness backlight upgrade (largest impact)

• BEF / DBEF brightness enhancement films

• High-transmittance polarizers

• Optimized optical stack design

• Full optical bonding to reduce reflection

• Display driver parameter optimization

The optimal solution always depends on the specific application scenario.

With over 15 years of experience in differentiated display and touch solutions, FANNAL supports industrial, medical, outdoor, and custom applications with engineering-driven designs. If you have display or touch requirements, feel free to follow us or contact our team directly.

FAQ

Q1: How do I choose the right brightness level without over-designing the display?

Brightness should be defined based on real ambient light conditions, not by aiming for the highest nits value. Over-design often leads to unnecessary power consumption and thermal stress. A balanced design considers brightness, viewing distance, surface reflection, and duty cycle together.

Q2: Why do two LCDs with the same nits rating perform very differently outdoors?

Because nits alone do not represent sunlight readability. Factors such as cover glass reflection, optical bonding, surface treatments, and viewing geometry significantly affect perceived brightness in outdoor environments.

Q3: What is the biggest risk when increasing LCD brightness in industrial equipment?

The primary risk is thermal management. Higher brightness increases heat generation, which can reduce backlight lifetime and system reliability if not properly controlled at the design level.

Q4: At what stage of a project should brightness requirements be finalized?

Brightness should be defined during display selection or early system design, especially for outdoor, medical, or battery-powered devices. Late-stage brightness changes typically increase cost and limit available technical options.

Q5: Is high brightness always necessary for outdoor or semi-outdoor applications?

No. In many cases, reducing reflection and improving contrast can be more effective than simply increasing brightness. The optimal solution depends on usage time, sunlight exposure angle, and enclosure design.