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Last Updated : 28-Aug-2007
Issue Number : 8000000402
Category : Image quality
Description : Ripples appear in the image when photographing an object with fine plaids or stripes.
The Moire Effect
Here describes the symptom, cause and prevention of the moire effect.
[The symptom of moire effect]
When you are shooting the object with fine regular pattern such as stripes and grillage, the ripple that does not exist on the object sometimes appears on the image.
Here is the example as shown in the pictures below.


The image on the right is the distanced shot of the image on the left that shows the shirt in fine grillage pattern. You can see the ripple that is not contained in the object in the image on the left.
This is the effect called moire effect.
[Why does the moire effect occur?]
Digital cameras and camcorders are loaded with the imaging devices such as CCD sensor and CMOS sensor that contain the pixels, converting the light into the electronic signal, aligned finely in both horizontally and vertically. When the regularly aligned pixels and the fine regular pattern of the object overlap slightly misaligned, the interference pattern occurs and the ripple that does not exist on the actual object may appear. This is the moire effect.


See the image above. This is the image showing red-grillage and black-grillage overlapped slightly misaligned. When you see the entire image, you can find the ripple that differs from either of the patterns. This is caused by the moire principle as well.
[Prevention of the moire effect]
You can decrease this effect by changing distance, zoom setting or the angle of the image. If you use the camera with manual focusing, the moire effect can be reduced by simply changing focus slightly.
[Reference]
You may find another moire effect on LCD of the camera. This is caused by regularly aligned pixels on the LCD, therefore, this effect does not necessarily appear on the images you have taken.

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