I never had this problem in previous versions of Photoshop, but I'm now using Photoshop CS and trying to scan a photo that I don't have the original of, just a printed copy of it. I keep getting a really strong moire pattern. In my old darkroom days, I used to just tilt the photo slightly one way or the other and it would help to eliminate the chance of getting a moire, but I've tried this on my scanner and it doesn't seem to help. Can anybody give me any tips on how to eliminate this problem? Thanks for any help you can give.
#1
1. do you have permission to use this photo?
BTW scanning screened material moire has always been an issue.
2. tilting is good.
3. scanning sofware usually has a descreen function, use it.
4 scan at high rez, blur then reduce.
#2
You have always had this problem.
Stop doing it.
#3
Well, I haven't.
I have an old High School year book from many years ago which has been damaged. I tried scanning one of the pages in, and got such a heavy moire, I just gave up on ever fixing it. If there's a way to correct for this, I'd love to know it.
I have tried the high resolution scan, BTW. I don't know how this was printed, but you can pretty much see all the dots. Not good...
#4
* Rotate the picture a bit, then fix in PS after scanning. * Scan at 600 ppi. (You will downsample later.)
* Set view to 100% then Filter > Noise > Median with Preview on. Keep increasing the amount by one pixel until you can see no or very little moire.
* Resample to 50% or (probably better) 33.33% using Bicubic Smoother. * Add a little (not too much) USM.
#5
Hi, Scott--
Thanks very much. I'll definitely try it.
All My Best,
Jeffrey
#6
I run into this problem with certain photo restoration tasks. Your best bet is to familiarize yourself with the Fast Fourier Transform (fft) filter.
Unfortunately, this filter does not exist for the Mac version of photoshop so you might have to find a stand-alone app. I would love if Adobe would implement such a filter in a future release.
Nikos
#7
Rotating 15 degrees is what usually helps, if you have a good way to measure. It splits the difference in screen angles and can be very effective in getting rid of moiré, or at least making it more manageable. Scanning at the highest optical resolution, assuming you're not on a drum scanner, blurring, then adding noise to the high res before downsampling are very effective. These techniques are best when the scanned piece is being reproduced quite a bit smaller than the original. If you're printing anything close to the same size, all bets are off in terms of quality.
#8
"3. scanning sofware usually has a descreen function, use it."
Before you try anthing else I you should try step 3. Even on the cheapest scanner these days the descreen functions work amazingly well.
In the past I've tried all sorts of rotates, blurs, despeckles to all channels, some channels, et al and almost always the descreen while scanning works the best.
alan
#9