Does digital capture guarantee moire patterns?

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I work for a design company directing the photography of architectural interiors. Man-made interiors are frequently decorated, most often with patterned laminates and fabrics. The chief problem we've encountered using The Nikon D1 and other digital cameras lies in the inevitable conflict these geometric patterns have with the CCD chip. In short, our interior shots are marred by the presence of moire patterns that distort and discolor the interior surfaces we document.

Because the patterns on walls and fabric are unevenly lit and foreshortened by perspective, no simple computer program will eliminate moires. Photoshop has no easy way to cut and paste our way out of these attention-getting artifacts.

So far this artifact is the chief obstacle we've encountered in converting to digital photography.

Has anyone or any software program successfully eliminated this problem?

-- mark skullerud (mark.a.skullerud@teague.com), March 24, 2000

Answers

I've never tried to address your problem, but I've got some ideas that might work if you willing to sacrifice some resolution.

What you are describing is called "aliasing" and happens when the sampling resolution is too low or improperly filtered. I don't see digital cameras getting away from this until they start sampling the image at a much higher resolution than they are storing. The correct solution is to sample at a much higher resolution (super-sample) and then re-sample it back to a lower resolution (this is called "anti- aliasing", btw). Given that you can't do this with your camera, here is an idea that I thought of (not guaranteed to work--I haven't yet tried it):

Take your pictures at the highest resolution possible (On the D1 this might be one of those YCbCr or native Tiff formats), add a small amount of random noise (experiment with the types & amounts), and then resample the image to a lower resolution. You might also try some bluring functions before you reduce the resolution. When I say reduce the resolution, I mean you have to at least go down by a factor of 2 in each dimension. Going down by a factor of 4 in each direction works well with computer graphics, but obviously this would shrink your image down too much for you to get a decent print.

At this point you can print it, or try to resample back up to a printable resolution.

Good luck!

-- Robert J Kyanko (rkyanko@home.com), March 24, 2000.


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