OnePlus, like many other Chinese smartphone brands, has added DC Dimming as an optional display feature. If you’re unfamiliar with DC Dimming, it’s an alternative to Pulse Width Modulation (PWM) that involves dimming the screen by adjusting the DC current. It’s useful for reducing screen flickering at low brightnesses, but it comes at the cost of quality. Many of you may not notice this screen flickering in your day-to-day use, but some people are more sensitive to it and may experience significant eye strain at low brightnesses. DC Dimming debuted on the OnePlus 7 Pro and was later added to the OnePlus 7 in an update. Today it got releases to One plus 6 / One Plus 6T in OxygenOS Open Beta 23/15 Changelog. The feature is accessible in OnePlus Laboratory in Settings > Utilities. Below are the changelog’s for the today’s update.

What is DC Dimming?

The most inexpensive solution to lower display brightness of LCD and OLED screens is PWM (or Pulse-Width Modulation).

In the context of LCD displays that have a backlight, PWM is about switching the backlight on and off at high frequency. This is done at a fast pace and your eyes perceive the combined effect as low brightness. For instance, to achieve 50 percent brightness, the backlight needs to be on and off for the same time.

PWM at 50% brightness. Backlight or OLED is active for half cycle

However, the problem is that some people are more sensitive to this backlight switching and are affected by this flicker, particularly at low brightness. For such users, using phones that use PWM in low light results in eye fatigue, severe headaches, and migraine

Source: Android Developers

DC Dimming, on the other hand, is simple in theory and the most obvious way of reducing brightness. It involves reducing current or voltage through the backlight to lower the brightness.

DC Dimming, however, isn’t easy to implement for OLED screens, the kind OnePlus uses on its phones. This is because, in AMOLED displays, each pixel is powered separately and reducing the voltage or current through these OLEDs also causes a shift in color.

Which is to say, with DC Dimming, you will notice different colors at different brightness levels. So, OEMs resort to passing high current through OLED at all times and maneuver off periods in the PWM cycle to lower brightness. 

Images shot at minimum display brightness

This is also why OnePlus has listed Dc dimming as an optional feature in Laboratory. Colors take a hit and thus users who aren’t sensitive to PWM or flicker have the option to opt out.

Going by our experience, there is no substantial downgrade in colors even when you turn on DC Dimming on OnePlus 7 Pro.

How other manufacturers like Samsung, Apple, and LG reduce brightness on AMOLED displays?

Manufacturers like Samsung, Apple, and LG use PWM in combination with Analog brightness control to reduce flicker on their OLED screen for smartphones and TVs. In this approach, the initial dimming is done by reducing the current through OLEDs, and for low brightness level, PWM is applied.

Image shows iPhone X display brightness; PWM impact kicks in at below 50% brightness

Source: IXBT

Xiaomi is another OEM who has added DC Dimming support to Mi 9. The Black Shark 2, which is a gaming phone manufactured by Xiaomi’s subsidiary also has DC Dimming support.

Oppo has started offering DC Dimming as Flicker-free display option in its high-end phones.

Huawei still uses PWM and screen flicker is very prominent on flagships like Huawei P30 Pro. The good thing is that the DC Dimming option can be pushed via an OTA update.

List of AMOLED display phones that support DC Dimming?

  • OnePlus 7 Pro and OnePlus 7(support will be extended to older OnePlus phones as well)
  • Black Shark 2
  • Xiaomi Mi 9
  • Xiaomi Mi 8
  • Redmi K20 Pro and Redmi K20
  • Oppo Reno 10X Zoom

PWM isn’t the only cause

Low refresh rate (below 60Hz) display or low refresh rate videos can also add flicker. Another factor is scrolling or fast animations on low refresh rate displays.

To protect your eyes from flicker, avoid using your phone in a dark ambiance as far as possible. You can also opt for high refresh rate screens and monitors (greater than 120Hz) at the workplace.

If you are using an OLED display phone, it’s advisable to avoid using it at minimum brightness for watching videos.  iPhone X, for example, doesn’t show flicker at 50 percent brightness but shows strong flicker at lower brightness levels. But that’s not always a solution. Huawei’s P30 Pro shows excessive flickering at anywhere below 100% brightness. 

How to enable DC Dimming on OnePlus phones

The option is currently available only on the 7 Pro and 7. You can also turn on DC dimming right before night time usage and turn it off later. An automatic scheduler would have helped.

 

Step 1: Open the main Settings menu and scroll down to Utilities.

 

 

 

 

 

 

 

Step 2: Now tap on OnePlus laboratory and turn on DC Dimming.

This is surely something people sensitive to flicker will appreciate.


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