computer screen shaking through mirror

[AndrewTheSinger]

I was eating this salty cookie that is very crisp, so when I chew it breaks and crackles causing some weird effects in my vision. When I was chewing it looking to my computer screen through a mirror I noticed the screen was shaking, but  only the screen, not the monitor nor anything else.

I tried to jump to see if it was just the motion of my head but it didn't happen as noticeably as when I was chewing. I tried shaking myself vigorously and it didn't work. Tried shaking my head and it didn't work.

When I jumped I could actually see the screen shaking a few seconds after I landed and stood still. But mostly through the mirror.

When I was chewing looking straight to the screen without the use of a mirror I didn't see see it happen as noticeably.

Video cameras can capture this motion on pc screens, I believe it has to do with the refresh rate, but our eyes can't see it.

It didn't happen with the tv though.

Could it be I am seeing that same thing due to an abnormal effect the act of chewing causes to my brain? Could anyone test it and reply? Anyone can explain?

[James S]

What you've experienced is a known effect.

When you chew, or click your jaws together, you are very quickly and very briefly causing your eyes to jump ever so slightly.

If you do this while looking at a monitor that is running at a slower refresh rate, say around 60Hz, that slight jumping of your eyes is just enough to catch the refresh, or scanning of a CRT monitor. A CRT redraws the entire picture from top to bottom many times a second. The refresh rate that you can set via your video card properties can speed this up, which will make the picture look clearer and smoother or softer. You're less likely to experience this effect if you have your monitor's refresh rate set from 85 to 100Hz, and you can't see it happening at all on LCD monitors, as they don't need to refresh. You'll probably notice it a lot more if your looking at a monitor under flourescent lighting.

I first experienced this many years ago when I used to work with the very early Macintosh computers, as their inbuilt screen had a slow refresh rate.


James.

[GANAMOHA]

you can get the same effect brushing your teeth with an electric toothbrush also try looking at a didgital watch like one into the wall

[AndrewTheSinger]

Oh that's cool man. Thanks for the nice explanation.
I'll try with the digital watch :}