The wierd lines effects that appear on photos of computer/tv screens.

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The wierd lines effects that appear on photos of computer/tv screens.

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Your TV’s screen is made up of pixels, with lines in between them.

Your camera’s sensor is also made up of pixels, with lines in between them.

When the TV’s lines and the camera’s lines don’t line up, or are different sizes or spaced differently, you get odd extra patterns that show up. This is called the Moirè effect. Basically, you’re seeing one set of lines overlaid on another set of lines, and so you will see a different periodic shape that’s the difference between the two line spacings.

I (kinda) know that, with filming, older video signals could be interlaced (NTSC), so the camera filming the TV could be using a frame rate that occasionally catches the imperceptible-to-human-eyes frame transitions. Would love to know more though.

TVs/monitors don’t display a constant image, they alternate lines of the image which produces the line effect when you take the photo because the camera is only seeing a fraction of the moment the alternating line is on