[SOLVED] Moire pattern in the newspapers and also "halftone dots" and "sampling grids"

Moire pattern in the newspapers and also "halftone dots" and "sampling grids"

I know about the moire patterns but I couldn't quite understand about the Moire patterns that we see in the newspapers. I saw this picture




I don't quite understand the moire patterns in this picture. The book says "The moire pattern in this image is the interference between the 45 degree orientation of the halftone dots and the north-south orientation of the sampling grid used to digitize the image". I am quite confused with this sentence. In addition I don't quite understand about the "halftone dots" and "sampling girds". Especially-----

What are "Sampling grids"?

---------- Post added at 17:53 ---------- Previous post was at 17:44 ----------

I got it guys. I misunderstood. This is the scanned image of the newspaper right? I thought this was the image in the newspaper. Anyway, now I understood everything.

Re: Moire pattern in the newspapers and also "halftone dots" and "sampling grids"

Does the article mention how to avoid the moire pattern? Namely to turn the photo an odd amount of degrees? Then scan it.

No inteference patterns from the two halftone grids.

This is a similar problem as when they first tried color printing of halftone pictures. They printed red separately. Then yellow. Then blue. And black.

Moire patterns resulted.

It didn't help to turn the color sampling grids at 45 degree increments. The result showed moire bands (or checkerboard, etc.). Same as in the photo in your post.

They tried different angles. They found they could solve the problem by turning the sampling grids at 30 degree angle increments. An easy solution and it's been the industry standard.