Vas is correct but let me elaborate one thing. The artifact from the camera is distinct from a rare but possible hum bar created by a ground loop problem. This hum bar is visible to the human eye and appears to move upward slowly.
Another problem, not to be confused with the other two, is loss of sync signals. This will cause shuttering and bending.
All of these things are undesirable and are not normal for CRTs.
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Re: CRT-aperture GLSL shader
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Re: CRT-aperture GLSL shader
