What is moir??
Sometimes odd stripes or colors will appear in a digital image, either from a high-end digital camera, or from a scanned image. This effect is called moir? and is caused when a fine pattern in the subject (such as the weave in a fabric or very close, parallel lines in architecture) matches the pattern of the imaging chip. When two patterns meet, often a third, new pattern is created. This third pattern is called moir?. Notice in the illustration below the round, circular patterns (on the right) created as the two grids are combined; this is moir?.
In order to reduce (or eliminate) moir?, a special anti-aliasing filter is mounted in the camera. If too strong a filter is mounted an overall soft image will be produced, but with no moir?. If a weaker filter is chosen the image will be sharper, but there is more of a chance for moir? to happen in some circumstances. Nikon has chosen to produce the sharpest image that can be made, even though there may be some moir? in parts of some images.
Notice the red/blue stripes on the bottom of the bag (which should be solid grey)
To help reduce moir? there are many techniques to use:
Change angle of camera.
Since the angle of the camera and subject causes moir?, slightly changing the angle of the camera (by rotating the camera) can remove or change any moire that is present.
Change camera position
Again, changing the angle relationship by moving left or right, up or down can reduce moir?.
Change focus point
Moir? is caused by very sharp focus and high detail on fine patterns; slightly changing the focus point changes the sharpness and can help to remove moir?.
Change lens focal length
Different lenses or focal length settings can be used to alter or remove moir?
Remove with software
Nikon Capture (as well as several third-party, Adobe® Photoshop® plug-ins) can be used to remove any moir? that does appear in the final image.
Of course it may not be possible to remove all moir? in all cases, but in general an overall clean, sharp image with slight moir? is preferred over a soft focus image.
Moir? can happen with images from all digital cameras and scanners, but is more likely to happen with an SLR-type digital camera system because the lens, sensor and software are designed to produce the sharpest, most accurate image possible.
When reviewing images to see if moir? is present be sure to be looking at the image on the computer screen (or the camera's LCD) at the full, 100% view. If you zoom out on-screen a false moir? can be produced by the pattern of the monitor grill.
Aug 30, 2005 |
Nikon Coolpix 3200 Digital Camera