Well, it is a result of the digital age and digital cameras. As most of you know, photosensors in most digital cameras are made up of pixels, light gathering spots on a sensor. Pixels are usually arranged in a rectangular pattern. (FYI, Fuji has a history of creating pixel arrangements that are not rectangular, with some diagonal, and a recent camera that has a "random" arrangement.)
When the subject has a repeating fine pattern, such as some fabrics, this pattern can interfere with the pixels in the camera sensor, creating images with strange patterns. These image patterns are called moire.
Recently I had my first real experience with moire. I was photographing an iPad screen, which was used by an environmental control system. As most of you know, computer displays are also made up of small pixels, in a rectangular pattern. As I photographed the iPad screen, I couldn't see the moire well on my small camera display, but when I got back to my office and examined the captures on my computer display, OMG, was it bad! You can see it here, especially in the detail view. I have circled the section of worst moire.
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| Original with obvious moire |
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| Detail of the moire |
I attempted to fix it, in Photoshop, using a few standard techniques. However, because the image contained only moire in the right side of the image, none of them worked well. I had to reshoot the screen.
The reshoot had to focus on eliminating the interaction of the pixels on the iPad with the camera pixels. I also had to eliminate any reflections, which had other complications. The easiest way to eliminate the moire was to tilt the camera, and orient the 2 sets of pixels at a large angle. Sure enough, this worked great.
Here is the 2nd image:
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| Final image, captured at an angle |
Now, you can see that I have an extra step in post-production; I have to straighten out the iPad. Since we have a moire-free capture, tilting it back straight keeps it moire-free.
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| Straightened moire-free final image |
So this solution was easy. And now I'll be much more conscious of that nasty beast called moire.
Thanks for reading.
Greg Sprenger
Constructed Images LLC
www.constructedimages.net
greg@constructedimages.net
