Moire Pattern with digital images

Is there a good technique for removing moire patterns in digital

photographs with PhotoShop 6?

when you scana half tone image, like the one you aooarently posted which on

your scanners descreener feature.

This image was not scanned. It was taken with a digital camera, and shipped to us on disk as a color tiff file. The Moiré pattern was discernable in the color image but was intensified when we converted it to a bitmapped image for printing.

<a href="http://www.creativepro.com/story/feature/10744-1.html">Scanning 101: No More Moiré</a>.

Christo,

 

I'm afraid that image <u>was</u> scanned from a newspaper or the sender photographed the newspaper with a digital camera. No original image from a digital camera will have that much interferrence in a clear sky.

 

Graeme

When shooting hockey games with my digital camera; every couple "roll/smartmedia" or two I get a moire pattern from a Hockey Refs/Linesman Jersey with the vertical black and white stipes. This happens when the Ref/linesman is far enough away that his jersey stipes are almost aligned with the pixels size. Maybe they are also slightly moving; as the pixel/scanner array is strobed/read. It is a weird effect that only happens at rare times. If I locate an old dud with this artifact; I will post it. I have never seen the effect with a Nikon or Leica at the asme rink in 5 years; only with a digital camera.

"Is there a good technique for removing moire patterns in digital photographs with PhotoShop 6?"

 

It's best to use a �Descreen� filter at time of image capture, also sample at 2X more than the desired resolution so you can apply a despeckle or blur filter, and resample to half size to eliminate the moire effect. A scanner may be a better choice for the original capture than a digital camera.

 

Another very simple trick to try is a slight rotation the capturing CCD either by tilting the camera or moving the print on the scanner bed, I�ve had quite a spectrum of �mixed� luck with this technique (sometimes better, sometimes worse!)

 

However if you're dealing with someone else�s image and can't get a correctly descreened capture: Then in Photoshop 6 it's worth a try to use the following Menu selection: Filter; Noise; Despeckle. Also try Filter; Noise; Median Filter. Still not happy, try Filter, Blur, Gaussian Blur. You'll have to vary the settings in each filter to see what works best for the image in question, since there aren't any �exact constants� that work for all patterns.

 

Ethics Note: Scanning images in printed material carries special tribulations of copyright. Please do be sensitive to the implications of the aforementioned. Thank you...

I repeat; this image was not scanned. The original image was 72 dpi, 14.222 inches x 10.667 inches. These numbers are consistent with other digital camera captures that have been received in the past. I doubt anyone would scan an image at that resolution. I have seen this effect a number of times in the past year, always with photographs of houses although not as severe as this. In her book, PhotoShop Restoration & Retouching, Katarin Eastman shows an example of a digital camera capture with moire pattern (p108). Her solution is software called Quantum Mechanic, something I am not able to afford at the moment. A PhotoShop solution would be preferred.

As I read it: <P>--You are saying the image was made using a digital camera

and that the object photograph was of a houston, not of a photograph of a

house. Am I correct?<P>

--What is the file size of the image ?

"the object photograph was of a houston"-afraid I am not folowing this. What is a houston? The photograph was of a house. The file size was 5.5 MB

Perhaps the problem is in terminology; what you have posted looks like a

digital photo (or scan) of a PRINT of a house. Did you not post a digitally

photographed laser print, newspaper, or other IMAGE of a house?

 

There is moire visible in the siding; that's because the frequency of dots in

the PRINT is close to the frequency of lines in the siding.

 

You can either print with a different dot/inch setting, change the dot screen

angle, or blur the image.

I should have also mentioned - since you say the original is in color - you can

convert to L*A*B Mode, guassian blur the A and B channels, leave (or even

sharpen the L channel) and convert back to RGB/CMYK.

Sorry to be so late in getting back to you. I don?t know what I can tell you. Most of the digital evangelists and pros that I have talked to have not experienced this problem. I encounter it on a daily basis however. The only other person who likewise expressed similar problems was an architectural photographer. Most of the photos that I see with the problem are of houses or similar structures.

 

What I suspect is that the linear array of roof tiles, brick walls etc, must fall into a similar linear array on the CCD or CMOS of the digital camera. Since I am a traditional 35-mm photographer, I am unable to tell if this is a problem with some digital cameras, or a particular brand.

 

I can tell you that I have developed some tips from various sources, which may or may not alleviate the problem. Always shoot at the highest resolution your camera will allow. If your camera has a daylight/overcast mode, set it in the overcast mode no matter what the situation is. Always use the fill flash. Bracket your photographs, and try tilting the camera a slightly different angle each time. Again, these have not been tested by me so if they help please let me know.

 

There is also a technique that I have used with some success in the production stage. Enlarge the photo to 100% in PhotoShop. Do a Gaussian Blur with a radius of 1.5 pixels. Reduce the image in the image size menu to 50% of the original. Do an unsharp mask: amount 200%, radius 1.0 and levels at 14. You may have to do some more sharpening, but I have found that usually the sharpen edges, or sharpen more filter will bring the photo into focus.

 

There are some third party software plugins for PhotoShop that I have tried, but with very, very limited success. Grain Surgery seems to do some good, but I have only just received the update (Grain Surgery 2) and have not been able to try it out yet. Camera Bits does have a moiré remover but I have been unable to make it work successfully.

 

If you discover any tips, tricks or techniques, I would appreciate it if you would pass them along.