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RC4 Knowledge Base

Set PWM Frequency to Eliminate Video Artifacts

This video demonstration is on the RC4Magic S3 DMX4dim device.

ISSUE : Banding, beating, and other visual artifacts can be an issue when working with video. In this example, both dimmers start at the default setting of 615Hz.

FIX : Increasing the PWM frequency resolves this: Press and hold the Set B ButtonSet B ButtonAll RC4 dimmers have Set buttons for each individual dimmer output. The second button is the Set B button. On a 2-channel device these are Set A and Set B buttons. A 4-channel device adds Set C and Set D. The most common use of the Set button is to assign a DMX channel and […]
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and it will flash a pattern on DimA and DimB outputs to indicate that a PWM frequencyPWM frequencyPWM stands for Pulse-Width Modulation.  It is a method for using a switching device (one that can only be on or off) to create what appears to be analog changes in level.  This is done by switching on and off at a high speed and varying the proportion of the time for each.  For example, of the […]
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increment has been made. It will automatically move to the next available frequency. The flashing pattern is different for each available frequency, indicating which frequency has been selected.

NOTE: The default PWM frequency is different for different system families:

RC4Magic 2.4GHz and RC4Magic-900 dimmers default to 615Hz, ideal for human eyes in a live performance environment

RC4 LumenDim and W-DIM dimmers default to 5kHz, ideal for video capture at normal frame rates

Each long-press of the Set B button increments to the next PWM frequency:

  1. 615Hz (default)
  2. 1.2kHz
  3. 5kHz
  4. 10kHz
  5. 20kHz
  6. 40kHz
  7. The next long-press cycles back to #1 (615Hz)

 

The correct PWM frequency will eliminate visible artifacts:

A. The flashing pattern on DimA/DimB is different for each available frequency, indicating which frequency has been selected.

B.  A chart of PWM frequencies clarifies all of this.