分析：LED大屏如何征服「镜头焦虑」？

行家说Talk · 2025-05-20

随着视频时代到来，视觉化的大屏影像成为了朋友圈的流量密码，但是总有那么些LED屏幕与摄像头“不太对付”，在拍摄LED大屏时，频闪、摩尔纹、对比度下降、锯齿等问题频频暴露。

对此，为此行家说Display用手机镜头以频闪为主题作了一场调研，面向以下问题：

哪些LED屏幕可与镜头完美配合？

为何肉眼下绚烂多彩的屏幕，却难以通过镜头的考验？

如何让LED屏幕适应拍摄需求？

案例拆解：

哪些LED屏幕可与镜头完美配合？

首先开启手机慢动作模式（240fps），以较近的距离（1-2米）随机拍摄近20款LED显示大屏，然后在电脑中放大观测显示屏细节的频闪程度和残影效果。

VP/XR大屏分类下，慢动作模式下基本没有频闪现象，且25%产品可同时实现「无频闪+灰阶稳定」；

LED演艺屏：相较于专业显示，演艺屏频闪现象整体更多，也有14%产品在慢动作特写可同时实现「无频闪+灰阶稳定」，但汇集演唱会实地远景拍摄时，30%屏幕可满足需求；

LED电影屏：闪烁问题普遍存在，尚未出现完美「无频闪+灰阶稳定」的屏幕，不过LED电影屏并非拍摄场景，产品需求多落在色度表现。

实验验证：

高刷新影响拍摄结果

根据拍摄的近20款LED显示大屏来看，无闪烁的产品通常具有高刷新率，当然也有显示屏辅以光学扩散膜等降低摄影中出现的问题。

仅针对高刷新，我们设置了对照组，以驱动IC是否开启「低灰倍刷」功能的显示屏幕作对比。这里使用两种拍摄模式。

首先使用手机慢动作模式拍摄，可以发现没有开启低灰倍刷功能的箱体频闪严重，且画面也有灰阶流失问题。

第二种模式，我们开启手机的专业摄影模式并调动快门，可以发现快门越快时，没有开启低灰倍刷功能的箱体显示问题越多；快门60时，已出现黑场现象；快门超过120时，可见频闪与灰阶问题。

综上可见，开启「低灰倍刷」功能会使得拍摄结果更佳符合人眼表现，高刷新率时，LED大屏更能满足多样化的拍摄需求。

总结：

高刷新+低灰共同保证拍摄色度表现

屏幕在镜头下的缺陷，本质是光电转换过程中的信息丢失。LED显示屏多是通过逐行扫描更新画面，人眼对图像的感知有约0.1秒的视觉暂留，能自动补全LED屏幕的间断刷新，但相机通过快门"切片式"采样，可能恰好截取到屏幕刷新间隙。

黑场问题的成因是因摄影机曝光时间未包含LED 显示屏中所有LED 显示时间。以两行扫设计的LED 显示屏搭配PWM 调光为例，LED 显示屏的画面显示会像图中是由上/ 下两部分轮流显示。

若是LED 显示屏的帧率与摄影设备的曝光时间发生每帧都不一致的状况，则可能产生闪烁的情况。

所以高刷新率，就是使用密集的刷新动作，让相机采集到的画面变化趋于连续，刷新率越高，允许相机的快门速度误差范围越大。

但需要注意，高刷新意味着每个帧的时间更短，如果PWM的周期与刷新率同步，会限制可用的灰阶数，因为灰阶等级取决于每个刷新周期内点亮时间的占比，可用时间单元压缩，即导致灰阶数下降。特别是在低亮度情况下，占空比降低，每个周期内有效点亮时间进一步缩短。

所以当前，行业推出了整合PWM+PAM技术的LED驱动IC，並可达到更高的灰阶表现，如聚积科技达芬奇方案，在高刷下仍支持19-bit灰阶（52万级亮度控制）。

不同的低灰倍刷设定在不同的灰阶下对应的刷新率有所不同，越高的低灰倍刷设定，在相同灰阶刷新数值越高，如灰阶值25时，使用16-bit PWM搭配32倍刷的驱动晶片已可达到7,680Hz的刷新率，此特性可有效改善拍摄的扫描线现象。

灯板实测低灰阶刷新数据如下图所示：

来源：聚积科技

所以，高刷新不是终点，拍摄场景下，高刷新的同时也需要注意保证灰阶，除了没有频闪外，拍摄影像也需求完美的色度表现，高刷低灰要同步实现。

英文版

Analyzing How LED Displays Conquer “Camera Anxiety”

In the era of visualization, LED displays are key to social media engagement. However, there are persistent issues, such as flickering, moiré, and low contrast. Hangjia Talk Dispaly is researching the 'flicker-free' ratio of these displays using smartphone cameras and aims to answer the following questions:

ü What kind of LED displays can perfectly meet the camera shooting requirements?

ü Why is it so challenging to photograph LED displays, even though they appear perfect to the human eye?

ü How do LED displays satisfy shooting requirements?

Case Studies：What Kind of LED Displays Can Perfectly Meet the Camera Shooting Requirements?

First, we tested our smartphone's slow-motion mode on 20 LED displays, capturing close-up (1m-2m) footage. We then reviewed the videos on monitors to identify flicker and ghosting issues.

ü XR/XR Displays: Overall, there are no noticeable flicker issues, and 25% of the products can achieve “flicker-free and no grayscale loss” simultaneously.

ü Rental Displays: Compared to professional displays, this category generally exhibits flicker issues. Only 14% of the products can achieve “flicker-free and no grayscale loss” simultaneously. However, from a distance, around 30% can meet the standard.

ü LED Cinema: There is no “perfect display” in this category due to flicker issues. However, cinema displays are not intended for photography; color performance is much more important.

Experimental Verifications: How High Refresh Rate Affects Shooting Performance

Based on the 20 recorded video footage, flicker-free LED displays typically feature a high refresh rate. Additionally, some LED displays use optical films to minimize issues during video recording.

To explore the impact of refresh rate, we created a control group to compare two LED cabinets—one with and one without the “Low-Gray Refresh Rate Function.”

We employed two different shooting methods:

First, we used the smartphone’s slow-motion mode to record the displays.

We observed that the cabinet without the “Low-Gray Refresh Rate Function” enabled exhibited noticeable flickering and grayscale loss.

（插入GIF）

Second, we switched to the smartphone’s professional mode to manually adjust the shutter speed.

We found that as the shutter speed increased, the LED cabinet without the “Low-Gray Refresh Rate Function” displayed more visual artifacts. At a shutter speed of 1/60, bands became visible; at speeds above 1/120, both flicker and grayscale loss were apparent.

Therefore, enabling the “Low-Gray Refresh Rate Function” improves visual performance during filming. A high refresh rate in LED displays ensures compatibility with various filming conditions.

Conclusion: A High Refresh Rate Combined with Low-Gray Performance Ensures Outstanding Color Performance

The visual defects observed by cameras result from data loss in the electro-optical transfer process. Most LED displays use scanning technology, refreshing images line by line. The human eye has a visual persistence of approximately 0.1 second when perceiving images.

This automatically compensates for the intermittent refresh of the LED display. However, due to the camera's slicing sampling method, it may still capture the refresh gaps of the screen.

Band occurs when the camera’s short exposure time does not cover the full refresh cycle of the LED display.

For example, consider a 2-scan LED display using PWM dimming. The display alternates between showing the upper and lower parts of the image.

Flicker primarily occurs when the signal from the photographic equipment is not synchronized with that from the display equipment. Let us assume that the LED display's frame rate and the photographic equipment's exposure time do not match for every frame. Consequently, the camera fails to capture a complete image. This leads to flicker due to the uncertainty associated with each frame captured by the camera.

Therefore, a high refresh rate entails more refresh actions, enabling the camera to capture continuous images more effectively. The higher the refresh rate, the greater the tolerance for deviation in the camera's shutter speed.

However, it is important to understand that a high refresh rate also implies shorter frame durations. If the PWM duty cycle is synchronized with the refresh rate, it may limit grayscale performance. This limitation arises because grayscale performance is dependent on the lit duration of each refresh cycle. When the lit duration is reduced, it results in lower grayscale levels. This is particularly evident under low brightness conditions, where the duty cycle is decreased, leading to reduced lit duration.

We now introduce the LED driver IC that integrates PAM and PWM technology to achieve enhanced grayscale performance. For instance, Macroblock’s DaVinci series can achieve 19-bit grayscale while maintaining a high refresh rate of 520,000 levels of brightness.

The figure below illustrates how different low-gray refresh settings result in varying refresh rates at distinct grayscale levels. The higher the low-gray refresh setting, the greater the refresh rate for a specific grayscale level. For example, at grayscale level 25, a driver IC utilizing 16-bit PWM with 32x low-gray refresh can achieve a refresh rate of 7,680 Hz. This feature effectively minimizes scan lines during filming.

The measured data on low grayscale refresh rates of the LED board is presented below.

Therefore, assuming that high refresh rates are not the ultimate goal is essential. In shooting applications, achieving a high refresh rate should not compromise grayscale performance. In addition to flicker issues, color accuracy must also be flawless. In conclusion, both high refresh rates and low-gray performance should be achieved concurrently.

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