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new way to check flicker without a camera

D

dopple

Gawd
Joined
Oct 5, 2011
Messages
685
This is experimental (could be wrong way to check) but a simple way to check flicker in my opinion without a camera.

Pull up a fullscreen document of black text on white background. Wear any tinted glasses i use amber colored ones so the screen doesn't blind you when you look at it without blinking.. stare at the text at eye level comfortably around 1-2 feet away from the screen for a few minutes without blinking or changing focus or moving your eyes. Be close enough to the screen so the edges of the screen cover your peripheral vision.

From your peripheral vision you'll notice the screen changing its luminance levels while you are still focusing on the text. This shows the screen flickers.

With this you can even check for PWM flickers or regular flickers in khz ranges. It will be visible in the form of rapid luminance changes full screen.

It is just experimental, Let me know what results you get from this or any comments.
 
Last edited:
Hello,

Different people have very different flicker sensitivities. The indirect method only works up to approximately hundred or two Hz (at least in my experience). I'd be surprised if it goes up to Khz leagues, but I'm not jumping to conclusions. However, I've posted some information about more well-known indirect methods of detecting flickers, in my References section on scanningbacklight.com -- the stroboscopic effect / phantom array effect is a more scientifically reliable indirect method for humans to detect Khz-league flickers. (the hand-wave in front of a flickering monitor/CRT, and the fast-moving mouse-pointer doubling/tripling/quadrupling effect on PWM backlights, are also related examples of the stroboscopic effect)

Other Information

There are many sources that show human eyes can indirectly detect visual phenomena running at many hundred Hertz, far beyond a human flicker fusion threshold. This information is included, because knowledge about scanning backlights is improved by knowledge about these topics.

Wagon Wheel Effect
- http://en.wikipedia.org/wiki/Wagon-wheel_effect
- http://www.michaelbach.de/ot/mot_wagonWheel/index.html
Example: An 8-spoke wagon wheel spinning clockwise 50 times per second under a 400 Hz stroboscope will appear to be stationary. However, if the stroboscope runs at 401 Hz, the wheel will spin slowly counter-clockwise. If the stroboscope runs at 399 Hz, the wheel will spin slowly clockwise.

Phantom Array Effect / Stroboscopic Effect
- http://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=1538&context=tpr (500 Hz detected)
- http://www.lrc.rpi.edu/programs/solidstate/assist/flicker.asp (300 Hz detected)
- http://www.lrc.rpi.edu/programs/solidstate/assist/pdf/AR-Flicker.pdf (10,000 Hz detected)
- http://cormusa.org/uploads/2012_2.10_Bullough_CORM_2012_Stroboscopic_Effects.pdf
- http://people.ds.cam.ac.uk/ssb22/lighting.html
Synopsis: Humans can indirectly detect a 500 Hz flicker via the “phantom array” effect: A fast moving flickering light source in a dark room, appears as a dotted trail instead of a continuous blur. This can also occur when rapidly moving/rolling eyes in front of flickering lights in a darkened room (e.g. old LED alarm clocks, neon lights, unrectified LED decoration light strings). Flicker all the way up to 10,000 Hz was indirectly detectable in some studies, in certain situations.

Rainbow Artifacts (DLP projectors)
- http://www.projectorcentral.com/lcd_dlp_update7.htm?page=Rainbow-Artifacts
- http://www.ausmedia.com.au/DLP_Sensitive.htm
- http://en.wikipedia.org/wiki/Digital_Light_Processing
Synopsis: Related to the phantom array effect, rainbow artifacts are observed by some people watching images from a single-chip DLP projector, even with 4X or 6X color wheel (240Hz and 360Hz). Fast eye movement causes white objects on black background to have a rainbow-colored blur (red-green-blue trails) instead of a continuous white blur.
Click to expand...
 
Last edited:
mdrejhon said:
Hello,

Different people have very different flicker sensitivities. The indirect method only works up to approximately hundred or two Hz (at least in my experience). I'd be surprised if it goes up to Khz leagues, but I'm not jumping to conclusions. However, I've posted some information about more well-known indirect methods of detecting flickers, in my References section on scanningbacklight.com -- the stroboscopic effect / phantom array effect is a more scientifically reliable indirect method for humans to detect Khz-league flickers. (the hand-wave in front of a flickering monitor/CRT, and the fast-moving mouse-pointer doubling/tripling/quadrupling effect on PWM backlights, are also related examples of the stroboscopic effect)
Click to expand...

nice set of links!
 
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