# Why is this picture "moving"? **URL:** \ **Category:** Factual Questions\ **Created:** [February 18, 2008, 1:06pm UTC](https://boards.straightdope.com/t/why-is-this-picture-moving/438094 "2008-02-18T13:06:48Z")\ **Posts on this page:** 17\ **Page:** 2
**Author:** ![elfkin477](https://avatars.discourse-cdn.com/v4/letter/e/a9a28c/32.png) [@elfkin477](https://boards.straightdope.com/u/elfkin477)\ **Post date:** [February 18, 2008, 4:44pm UTC](https://boards.straightdope.com/t/why-is-this-picture-moving/438094/21 "2008-02-18T16:44:25Z")
For me it’s a very ugly, but still, image. ---
**Author:** ![control-z](https://avatars.discourse-cdn.com/v4/letter/c/eada6e/32.png) [@control-z](https://boards.straightdope.com/u/control-z)\ **Post date:** [February 18, 2008, 5:08pm UTC](https://boards.straightdope.com/t/why-is-this-picture-moving/438094/22 "2008-02-18T17:08:42Z")
I think the dot movement on the flightsim pic has something to do with the refresh rate of your monitor. LCDs I believe are usually (always) 60Hz, CRT monitors can have higher refresh rates. People used to set CRT monitors to higher refresh rates to relieve eye strain. ---
**Author:** ![Pushkin](https://avatars.discourse-cdn.com/v4/letter/p/ee59a6/32.png) [@Pushkin](https://boards.straightdope.com/u/Pushkin)\ **Post date:** [February 18, 2008, 5:48pm UTC](https://boards.straightdope.com/t/why-is-this-picture-moving/438094/23 "2008-02-18T17:48:18Z")
OK, back home and on my laptop the image from the flight sim doesn’t repeat the moving trick. When I change the screen resolution down I get what I assume are moire patterns, but no effect of motion. However, the second picture keeps the effect no matter what the resolution. In fact, on this screen when I move closer or further from the screen it seems to amplify the effect, making it look like I’m viewing the object through a magnifying glass. ---
**Author:** ![Nanoda](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Nanoda](https://boards.straightdope.com/u/Nanoda)\ **Post date:** [February 18, 2008, 6:43pm UTC](https://boards.straightdope.com/t/why-is-this-picture-moving/438094/24 "2008-02-18T18:43:41Z")
I understand many LCD screens don’t actually do full 32 bit colour, and fake it by switching between two colours… perhaps it has something to do with that? ---
**Author:** ![chowder](https://avatars.discourse-cdn.com/v4/letter/c/977dab/32.png) [@chowder](https://boards.straightdope.com/u/chowder)\ **Post date:** [February 18, 2008, 6:49pm UTC](https://boards.straightdope.com/t/why-is-this-picture-moving/438094/25 "2008-02-18T18:49:08Z")
19" flat monitor, no movement ---
**Author:** ![Will\_Repair](https://avatars.discourse-cdn.com/v4/letter/w/a698b9/32.png) [@Will\_Repair](https://boards.straightdope.com/u/Will_Repair)\ **Post date:** [February 19, 2008, 3:58am UTC](https://boards.straightdope.com/t/why-is-this-picture-moving/438094/26 "2008-02-19T03:58:39Z")
[QUOTE=Pushkin] The grey bit of the picture appears to be in motion, is this because of the deficiency of my monitor, or an optical illusion? And if the latter, what causes it? [/QUOTE] Is your screen resolution “Interlaced” or “Non-Interlaced”? With an interlaced resolution the electron beam paints half a frame (a field) and then goes back to paint the other half. “Persistence of Vision” by the eye fools the brain into interpreting one full image. (Old movies seem in jerky motion because 16 frames a second doesn’t provide the persistence of vision that 24 frames a second does.) So, my theory is that you have an interlaced resolution setting on your monitor and the electron beam painting of one field, then the other field, to complete the frame is too slow (or too different) for your eye’s persistence of vision and thus you perceive motion. ---
**Author:** ![spinky](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@spinky](https://boards.straightdope.com/u/spinky)\ **Post date:** [February 19, 2008, 9:09am UTC](https://boards.straightdope.com/t/why-is-this-picture-moving/438094/27 "2008-02-19T09:09:35Z")
I think it has more to do with the pixels your computer is trying to display not perfectly syncing up with the actual pixel elements on the physical screen. I’m using an LCD with an analog (VGA) connection, and I saw the movement until I hit “auto-sync”, and then it got much crisper and sharper. If your monitor isn’t synced up exactly right and you make your desktop pattern a 1-pixel checkerboard, you’ll see a much more extreme version of this effect. Hit auto-sync and it goes right away. It’s a good way to make sure your signal is synced up nicely, because the auto-sync logic in modern monitors looks for pixel boundaries to help it figure things out, and a checkerboard makes it so every pixel boundary is very well-defined. ---
**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\ **Post date:** [February 19, 2008, 10:17am UTC](https://boards.straightdope.com/t/why-is-this-picture-moving/438094/28 "2008-02-19T10:17:24Z")
[QUOTE=Pushkin] From a link in an IMHO fantasy thread, [this link](http://en.wikipedia.org/wiki/Image:Flight_Simulator_2.13_-_Meigs.png) was posted to a screen shot of a flight simulator. The grey bit of the picture appears to be in motion, is this because of the deficiency of my monitor, or an optical illusion? And if the latter, what causes it? [/QUOTE] Mess around with your refresh rate. I had a similar effect a few days ago and changing my refresh rate got rid of it. -Kris ---
**Author:** ![Pushkin](https://avatars.discourse-cdn.com/v4/letter/p/ee59a6/32.png) [@Pushkin](https://boards.straightdope.com/u/Pushkin)\ **Post date:** [February 19, 2008, 10:29am UTC](https://boards.straightdope.com/t/why-is-this-picture-moving/438094/29 "2008-02-19T10:29:09Z")
Back in work, I checked the advanced graphic properties and my screen’s aspect ratio is maintained, if that is meaningful to anyone. But putting up the refresh rate and putting the screen DPI setting to “Normal” took away the effect on the first picture. ---
**Author:** ![Santo\_Rugger](https://avatars.discourse-cdn.com/v4/letter/s/e95f7d/32.png) [@Santo\_Rugger](https://boards.straightdope.com/u/Santo_Rugger)\ **Post date:** [February 19, 2008, 3:14pm UTC](https://boards.straightdope.com/t/why-is-this-picture-moving/438094/30 "2008-02-19T15:14:59Z")
[QUOTE=Will Repair] \(Old movies seem in jerky motion because 16 frames a second doesn’t provide the persistence of vision that 24 frames a second does.)\ [/QUOTE] Old movies seem in jerky motion because 16 frames are being converted to 24 frames without interpolation, and 16 doesn’t divide into 24 evenly. Therefore, when played back at 24 frames per second, 8 frames have to be shown twice. I’m sure about that part, but I’m not sure about the other thing I’ve heard; a confounding factor to their jerkyness is that audiences laughed more when the film was sped up, because it was funny to watch Charlie Chaplin move with his awkward swagger sped up. So, in reality, there were even less than 16 frames per second in the production, and closer to 12 of the frames had to be shown twice. ---
**Author:** ![Cervaise](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cervaise/32/16693_2.png) [@Cervaise](https://boards.straightdope.com/u/Cervaise)\ **Post date:** [February 19, 2008, 8:12pm UTC](https://boards.straightdope.com/t/why-is-this-picture-moving/438094/31 "2008-02-19T20:12:37Z")
Maybe it’s a tumor. ---
**Author:** ![Pushkin](https://avatars.discourse-cdn.com/v4/letter/p/ee59a6/32.png) [@Pushkin](https://boards.straightdope.com/u/Pushkin)\ **Post date:** [February 19, 2008, 8:50pm UTC](https://boards.straightdope.com/t/why-is-this-picture-moving/438094/32 "2008-02-19T20:50:07Z")
[QUOTE=Cervaise] Maybe it’s a tumor. [/QUOTE] When I was telling Mum, as a kid, about an annoying floater in my eye (that is still there today), that was her glib reply to me :rolleyes: ---
**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\ **Post date:** [February 19, 2008, 8:59pm UTC](https://boards.straightdope.com/t/why-is-this-picture-moving/438094/33 "2008-02-19T20:59:53Z")
[QUOTE=Pushkin] When I was telling Mum, as a kid, about an annoying floater in my eye (that is still there today), that was her glib reply to me :rolleyes: [/QUOTE] So… Is it a tumor? -FrL- 😉 ---
**Author:** ![robcaro](https://avatars.discourse-cdn.com/v4/letter/r/df705f/32.png) [@robcaro](https://boards.straightdope.com/u/robcaro)\ **Post date:** [February 19, 2008, 9:28pm UTC](https://boards.straightdope.com/t/why-is-this-picture-moving/438094/34 "2008-02-19T21:28:17Z")
15" LCD… No movement. ---
**Author:** ![rowrrbazzle](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rowrrbazzle/32/414_2.png) [@rowrrbazzle](https://boards.straightdope.com/u/rowrrbazzle)\ **Post date:** [February 19, 2008, 9:37pm UTC](https://boards.straightdope.com/t/why-is-this-picture-moving/438094/35 "2008-02-19T21:37:03Z")
The original doesn’t move for me. Flat panel monitor. The close-up does. I noticed that if I move my eyes around the circumference of the circle, the movement of the circle’s interior coordinates with my eye movement. So as **Squink** said, the motion in the close-up is some variety of optical illusion related to eye movement. ---
**Author:** ![Pushkin](https://avatars.discourse-cdn.com/v4/letter/p/ee59a6/32.png) [@Pushkin](https://boards.straightdope.com/u/Pushkin)\ **Post date:** [February 19, 2008, 9:54pm UTC](https://boards.straightdope.com/t/why-is-this-picture-moving/438094/36 "2008-02-19T21:54:01Z")
[QUOTE=Frylock] So… Is it a tumor? -FrL- 😉 [/QUOTE] After 20 years of being alive since then, it must be benign at the very least 😛 ---
**Author:** ![Will\_Repair](https://avatars.discourse-cdn.com/v4/letter/w/a698b9/32.png) [@Will\_Repair](https://boards.straightdope.com/u/Will_Repair)\ **Post date:** [February 20, 2008, 8:20am UTC](https://boards.straightdope.com/t/why-is-this-picture-moving/438094/37 "2008-02-20T08:20:00Z")
[QUOTE=Santo Rugger] …8 frames have to be shown twice. [/QUOTE] Good point. You bring up an interesting question. I’ve only seen 16 fps films on 24 fps movies. What would it look like in the original? [QUOTE=Pushkin] …putting up the refresh rate and putting the screen DPI setting to “Normal” took away the effect on the first picture. [/QUOTE] … [Previous page](https://boards.straightdope.com/t/why-is-this-picture-moving/438094.md?page=1)