Why do computer screens...?

Question

I've noticed that when you see a computer screen being shown on tv there are lines that run through it. Anyone else ever notice this? And why does it do it?

Answer 1

This may sound funny but here goes. TV cameras scan the image. I.E. they don't take a picture like a film camera does, they scan across the image in lines from top to bottom. I can't recall the exact number but it seems like it is about a 1000 scan lines per image. A computer monitor displays an image in the same manner. It scans something like 600 lines. Now your TV also displays by scanning across the screen. I'm not sure about HDTV but I think standard TV has 525 scan lines.

So when you get a camera scanning an image that is being displaying by scanning, then send it to another TV to display that same image by scanning, synchronization problems crop up. That is why you see the lines on computer monitors displayed on your TV during movies and TV Shows.

Basically it boils down to a camera trying to take a shot when there is nothing to photograph. Of course all of this happens in thousandths of a second. Too fast for the human eye to register, but it shows up just fine when you start mixing cameras and images. If you have a digital camera with a fast shutter speed available, try taking a half dozen shots of images on your TV. At one thousandth of a second you will probably catch the scan in progress in at least one of the photos.

I hope this is more help than confusion. I know it really had me walking and talking in circles when they were teaching it in my electronics school.

Hey, if I damaged you too much, contact me through my profile and I'll do my best to try to set things right.

Answer 2

it is due to the difference in refresh rate of the PC and the capture speed of the video camera. All this boils down to fps or frames per second. Your monitor has a refresh rate of around 50 mhz or fps to anywhere higher such 80 to 100 mhz. This means the screen actually changes 50 times per second. You won't notice this because the human eye only need 18 fps to create the illusion of motion.
Meanwhile, the video is basically a series of pictures taken at a very fast rate. If the video camera is taken pictures at a faster rate than the monitor refreshes, some parts of the monitor screen will be empty, causing it to flicker in the video.

Answer 3

Because an image forms on a computer in lines; the faster the "refresh rate" of a computer, the fewer lines you will see when the monitor is filmed. This was particularly obvious years ago with tvs because the electron guns scanned across so slowly.

Answer 4

It is due to the refresh rate of the computer screen as well as the scan rate of the camera. If they don't sync, you'll get lines. You'll get the same thing if you take a picture of a TV or computer monitor and your speed isn't set correctly.

10 ponts please???

Answer 5

Difference in speed of computer screen and TV camera.

Answer 6

it hapens only with crt (cathode ray tube) screens. on them the picture is created by the dots wich form lines, one below another. this hapens very fast, so you see only continious picture. (you chose the speed of this by refresh rate in your screen propertis, its hove you can slow it down so it will be visible on zour screen, but its anoying.) this somehow becomes visible when shot with camera, probably cause the camera makes certain number of pictures per second, instead of continious movement.

Answer 7

i bcoz of the voltage difference or some kind of electrical problems in the area the computer is installed...

The explanation is given below...

Answer 8

it just because of magnetic effect....bez computer screen pass ultravoilet rays dat get combine with recording rays ...and get affected....if u keep any mobile or ups near ur screen ..u vl get twisted image on screen ....

Answer 9

it's because you're watching old technology

Answer 10

can u be sum more precise plz