Photoshop noob needs to get schooled

November 19, 2011 7:54 PM

Photoshop gurus - can this scan be fixed? If so, how?

I want to scan a collection of images to share online, but I only have a craptastic scanner and all the images I've scanned so far have come out like the one I've linked. I don't use Photoshop very often aside from cropping, rotating and resizing pics. (I have CS4 if that helps with answers.)

I can't even determine what the noise pattern is on this scan - would this be considered moire? If so, is there so much of it that I'd be better off seeing if I can borrow someone else's scanner and start over? If it can be fixed in Photoshop, I wouldn't mind doing some gruntwork to make the scans look better.

posted by Anima Mundi to grab bag (16 answers total)

The time it would take to fix this scan in Photoshop is really, REALLY not worth it if you have any other alternatives. You would essentially have to retouch the entire image by hand -- I'm not even sure how much you cold automate this kind of work, and any automated fix would be messy and require a lot of correction regardless.

Can you tell us more about how you're scanning the image? What resolution, how many colors, etc? What kind of scanner do you have?

(qualifications: I'm a professional artist who's been working extensively with Photoshop since 1998 or so.)
posted by Narrative Priorities at 8:16 PM on November 19, 2011 [2 favorites]

That looks like moire to me. Try different settings, like glossy etc.
posted by sanka at 8:25 PM on November 19, 2011 [1 favorite]

Is this a scan of something from a magazine, or from a drawing on drawing paper? If it is from a magazine, there is nothing you can do about it. The type of printing used to make magazines (or newspapers) is different from a photograph, so when you scan that type of image, you see the printing process. Basically, printing a magazine uses a dot process that the scanner picks up, which is why your scan looks somewhat pixellated. Looking at your image again, i also think that perhaps you have a crappy scanner and did not scan on the highest dpi setting. when scanning an image you always want to scan on the highest dpi setting, because then you will get the highest quality image.
posted by ruhroh at 8:48 PM on November 19, 2011 [1 favorite]

Try scanning again with descreening on, maybe.
posted by drhydro at 8:58 PM on November 19, 2011

Try reading scantips.com, especially this page. That webpage is a bit dated (it's a web classic at this point) but since scanning isn't as popular as it used to be (thanks to digital cameras) there's not too many great resources for info on scanning anymore. In general you'll want to scan at the highest optical (non-interpolated) resolution your scanner supports and go from there... but as others have said, you may be better off trying a different scanner, and if your originals are printed then there's not too many options you have.
posted by reptile at 9:21 PM on November 19, 2011

I am not a photoshop guru, but as part of volunteer work I do, I sometimes I have process scans of this quality, with little option to rescan. The general technique you want to follow is:

(1) use gaussian blur to smooth over dotting (this should actually work pretty well, since at least your example image is mostly block colors without a lot of shading)
(2) Use an unsharp mask to re-sharpen the important lines in the image.

The settings for each of these filters are highly individual, so I can't really help you there beyond recommending that you play around. Also I will caution that this won't produce a perfect image, but it should be better, at least.

I would absolutely recommend rescanning (at the highest resolution possible) first if you can, but I still think you'll have to blur and then resharpen the image to get rid of the dot printing effects.
posted by muddgirl at 9:34 PM on November 19, 2011 [1 favorite]

Yeah there's a big difference between a noisy scan and problems with the scanner and this is the latter. The reason it looks like that is because your scanner is not picking up all the color depth correctly and is compressing multiple similar shades into one shade (with lines in it for gradations). You could retouch these images to look nicer but it wouldn't be worth the effort, and it wouldn't restore the original color depth and gradations.

Verify your scanner setting are right for starters. Is your scanning program automatically applying any file compression or color correction to your images? You can disable color correction and save in a lossless format and see if it looks better. If it does, batch processing changing file format is a cinch in photoshop.

If you have a decent digital camera and a tripod or a steady hand you might get better results taking pictures of these in a good strong light than scanning them. Something to consider.
posted by everyday_naturalist at 9:54 PM on November 19, 2011

There's moire in there for sure but it looks like something else is going on as well.

I suggest downloading the trial version of VueScan -- it works with a huge number of different scanners. The trial will watermark your images, but you'll be able to see if you still get the banding and color noise you see in your example scan.

If you do get the banding and color noise, you're better off trying to find a different scanner. If, on the other hand, the output from VueScan looks more like the original artwork you're scanning (other than the watermarking) the problem is with the software you're using -- either the settings you're using are wrong, or the software just sucks. (I've never seen pack-in scanner software that didn't suck, but some sucks more than others.)

As others have mentioned, it would help a lot to know what settings you're using (especially resolution and descreening).
posted by Lazlo at 12:11 AM on November 20, 2011

Tell your scanner to scan it at 1200 dpi (or whatever its native optical resolution is) and then pull it into Photoshop and resize it down to a sane size. Usually that "just works". If not, you'll have to experiment with gaussian blur or descreening.

It all looks like the result of halftoning. Our eyes can ignore the halftoning (things printed as dots of cmyk color), but the scanner's "eyes" get confused. You get the herringbone pattern because each plate of color is at an angle to the rest of them. So as the scanner moves down the page, some of the pixels it scans have one dot in them, and some have two dots in them.

What you need to do is kick up the dpi to a point where the scanner is fully imaging the halftone dots, (instead of one scan pixel picking up multiple dots, you have multiple pixels scanning a single dot). Once you've done that, you can use photoshop to resize (or descreen and then resize) and it should come out fine.
posted by gjc at 6:22 AM on November 20, 2011 [1 favorite]

it's moire
posted by colin_l at 6:46 AM on November 20, 2011

It's a while since I have done this, but have had some succes using the method muddgirl suggests, with the addition of applying the method separately to each of the rgb channels as required. I think scanning at highest res possible will also help, depending on how much time/effort you need/want to put into it, a high res scan can at least give you accurate outlines allowing you to recreate the image relatively easily.
posted by zingzangzung at 11:29 AM on November 20, 2011

Okay, the original scan is 24-bit color, no descreening, 96 dpi. It's on glossy paper, almost like a postcard quality. I'm using an Epson 3-in-1 machine (NX300 series.) I'll fiddle around with the dpi settings and try descreening if it's an option. If all else fails, looks like I'll just have to use a digital camera.

For this new scan I used the 1200 dpi as gjc suggested. The moire is still there, but definitely not as much.
posted by Anima Mundi at 12:17 PM on November 20, 2011

Yes, that scan looks a lot better! If you resize your scans to normal web browsing resolution and dimensions once they're in your computer (72 dpi, ~800-1000 pixels wide for something in portrait orientation like this) then I think they'll look about as good as they're going to. Although it would probably pay to mess around a little with different image sizes until you hit on one that looks best -- the moire effect can be kind of finicky, but you'll figure it out and then you'll have a system you can use for the rest of your images!
posted by Narrative Priorities at 1:31 PM on November 20, 2011

Ugh, moire. Scanner software should know how to descreen this off-set printed item, but you may, in fact, be better by photographing it and then working on that. (Speaking as an ex-service bureau guy, *ahem*.)

Wheeeeeen the screen
Hits your eyyyyyye
Like a big
Gridded of liiiiiiiines
That's a moiré!

When you seeeeee
Too much dots
Like a big old pen-plot,
That's a moiré!
posted by wenestvedt at 6:03 AM on November 21, 2011

If your scanner will let you, try to scan into a CMYK format. Open that file in Photoshop, split it to the separate channels, run the smoothing on each channel separately, and then recombine.

What may work is (somehow) converting the separate planes into a vector format. That process ought to smooth out the dots into gradients. After that, recombine the planes and export as a bmp or jpg.

This low-tech solution worked for me in the past, scanning baseball cards: scan it at the high dpi, and then open it with Irfanview and just resize it. The result I got with that was somehow better than what was printed on the cards themselves.

If you have a digital camera with a macro mode, however, that might be easier. One trick I've heard of for doing that is to put the zoom to full and physically bring the camera further back. That keeps the perspective as flat as possible, by making the angles narrower and because the image will only be going through the centers of the lenses.
posted by gjc at 6:49 AM on November 21, 2011

Sorry for the late response, but for the time crunch that I'm in for putting this collection online, gjc's answer does the trick. Thanks! I'll also keep in mind everyone else's suggestions for scanning/taking photographs in the future.
posted by Anima Mundi at 6:48 PM on November 26, 2011