Digital Cameras: What is Moire Pattern on Images?
A moire pattern is created when you take two grids and lay them upon each other at different angles. Originally, the word referred to fabric designs, but when we talk about it in an image, it's often an unwanted effect caused by numerous digital imaging techniques. Most colors in images are composed of different tones of black, cyan, yellow and magenta. Moire patterns often occur in images, but it's usually too small for the human eye to notice. When we refer to moire patterns in digital images, we're recognizing excessive patterns.
Understanding Moire Pattern
The effect is not entirely predictable either. Sometimes, when viewing the same image on different screens, one will have the effect and the other won't. Also, when down sampling an image, the effect can occur while the master is effect free.
When photographing people, you will find that the biggest cause of moire pattern is from the clothes they are wearing. This is more noticeable in video when the subject moves. This effect is also known as strobing, and you should discourage your subjects from wearing wardrobe that will cause this.
Other times, you will find the pattern in certain locations like a zoo cage. When the effect comes from the physical environment, there is little you can do besides find the least affected angle.