Just got a scanner...got a couple of questions

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Just got a scanner...got a couple of questions

2003-06-21 02:34:21

I just got a scanner and I am new to scanning and I was wondering if anyone could help me out with these two questions:

1). When I scan my cd covers they are displayed like a newspaper picture is printed....like a matrix of dots. How do I fix this?

2). Also, they scanning glass is clean, but with the light on I can see there is a film of soap. I cleaned the top of it but on the bottom it is still there. Should I take it apart and take the soap film off the bottom or will it not effect the scan quality if I just leave it there?

Thanks,
-Darin

Just got a scanner...got a couple of questions

Reply #1 – 2003-06-21 02:57:36

Quote

1). When I scan my cd covers they are displayed like a newspaper picture is printed....like a matrix of dots. How do I fix this?

There should be "descreen" function somwhere in your scanner's software. Try to adjust it.

Just got a scanner...got a couple of questions

Reply #2 – 2003-06-21 02:58:44

1) Within the scanner driver window there should be a setting for a "Descreen" that gives you some choices. That will remove the pixlated look.

2) Guess that depends on how tough it is to take the unit apart - go for it if you think you can get it all back together easily.

Just got a scanner...got a couple of questions

Reply #3 – 2003-06-21 03:36:41

Hi Darin

So which scanner did you get finally?

I have the Epson so I can only speak of the software which came with that (EPSON TWAIN 5) which has a checkbox for a Unsharp mask - although on some pictures you still get a moire pattern with it on - I needed to filter it out in photoshop to remove it (descreening process)

I don't know if I would remove that film? is it even or does it seem to be heavier / absent in areas? I'm just thinking it might be to diffuse the light source a bit?

What program are you using to edit the images?

Just got a scanner...got a couple of questions

Reply #4 – 2003-06-21 03:50:15

Hi TwoJ,

I decided to go all out and I ended up getting the Canoscan 5000f . I bought it off the internet and saved about $40.00. So far I am real happy with it. The soap film isn't even...it is absent in some places. I am using Arc photo Studio 5. It's awsome. I can't decide if I should the unsharp mask or not. I can't tell if it is just me but with it on the detail seems a little sharper but then the descreen doesn't seem to work as well and I can see a little of texture from the original. Do you use it or do you have it unchecked? Also, do you think the soap film could degrade the quality of the scans any?

Thanks,
-Darin

Just got a scanner...got a couple of questions

Reply #5 – 2003-06-21 04:32:35

ACtually I did a good comparision and diffently want the Unsharp mask turned off. The descreen helped alot, but the dot matrix pattern is still there. Is there anything else I can do to get rid of it?

Thanks,
Darin

Just got a scanner...got a couple of questions

Reply #6 – 2003-06-21 04:45:54

Good, I don't know that scanner but I was thinking of getting a Canon before I got the Epson. The Epson was just at a cheaper price

Sounds weird about the film - never heard of that before - I guess being the adventurous type i would take it apart to try and clean the glass but be aware that you are probably going to void the warranty if you do that.

Well the Epson unsharp mask seems to be a very weak descreening filter, so i leave it on for covers, there are still a fair number of covers that still need to have more demoire filtering done on them to remove the demoire effect on some scans. By the time I have finished reducing the scans to an appropriate size and converting to jpeg I can't tell the difference between a scan with and without the unsharp mask.

you might be interested in these pages I found about scanning artwork
http://www.wintektx.com/extras/cdart.htm
http://www.cdcovers.cc/faq.php
http://www.cdcovers.cc/scanman.php
http://www.corinium.freeuk.com/zaragon/h_coverscan.htm
http://www.bobsboots.com/How_to_scan.html

happy scanning

Just got a scanner...got a couple of questions

Reply #7 – 2003-06-21 04:53:42

That matrix dot pattern pattern is called the demoire effect -

What works for me is that since I do most of my post scan work in photoshop - it has a despeckle filter;
Filter -> Noise -> Despeckle
That seems to work well at removing it - you do lose some detail (which will result in a smaller file) but it is about the only thing I found that works at removing that effect.

You'll have to see if your software has something similar - never worked with Arc Photo

Just got a scanner...got a couple of questions

Reply #8 – 2003-06-21 08:10:26

Hmmm....when I scan a cd cover the cd cover is 4 3/4 by 4 3/4 inch and the Scanner scans it at 4.81 by 4.03 inch. Shouldn't the scanner be scanning it to the exact size of the object?

Thanks,
Darin

Just got a scanner...got a couple of questions

Reply #9 – 2003-06-21 08:23:44

Umm...nevermind. I figured it out....boy, i feel stupid. >_<

Just got a scanner...got a couple of questions

Reply #10 – 2003-06-21 18:24:20

In order to avoid aliasing on the moire, that is to have a very large moire effect, with dots sevral centimeters large, you have to scan in high resolution, then reduce the image later. 300 DPI is enough to capture all the individual printed dots, and avoid a moire effect. If you need more or less, keep using integer divisors of you scanner's optical resulution. Example, I've found that the Epson 1250 is a 1200x600 dpi scanner (scanning a coin at 2400 dpi). Thus I sould only use 150, 200, 300, 600 DPI for example, otherwise, the quality is inferior, and the moire effect could come back.

Then, you have two possibilities :

You reduce the picture enough so that the dots disappear.
You blur the dots using a "gaussian blur" filter. This is the filter used as an example in Photoshop's help files.
I've compared the gaussian blur with an FFT lowpass, and the FFT is barely better. Thus the gaussian blur filter is very effective for removing dots without adding too much blur.

Just got a scanner...got a couple of questions

Reply #11 – 2003-06-21 19:57:52

as pio allready mentioned, there is a resolution downscaling procedure (try 300 dpi, then 600dpi for example) and allready mentioned descreen filters.

1. also - scan the picture under different angles (as to reduce the problem, since the color dots are positioned in certain degrees around each other)
2. try to scan without descreen filters, then photoshop noise despeckle (also mentioned), then scale down and unsharp mask.
3. same as 2. but gaussian blur, then sharpen, then scale to 50%, then sharpen, scale to 50% ect to finally get the desired size. (edit: in the final size unsharp mask maybe, always the last filter)

there are plenty more possible procedures..., they depend on the way the image was originaly printed (resolution, dither.., ect) and also on the motive itself.

edit: also check http://www.hamrick.com/ (vuescan)

Just got a scanner...got a couple of questions

Reply #12 – 2003-06-21 21:37:37

Darin,

Since you figured out what you were doing wrong (according to your most recent post), could you let us know what it was, for the benefit of future buyers/users of the Canon scanner?

Otherwise the thread will continue to attract discussions of resolution scaling, speckling, gaussian blur, masking, moire patterns, soap films, and other effects that, while interesting, are probably not related to the actual problem you had.

No matter how foolish the error looks to you now, I guarantee you that others have done (and will do) the same (and worse).

Just got a scanner...got a couple of questions

Reply #13 – 2003-06-21 22:31:53

Well....it was like 3 oclcok in the morning and it was a really stupid error. I am required to have the image an inch away from the bottom of the of the scanner.

Just got a scanner...got a couple of questions

Reply #14 – 2003-06-21 23:55:01

Pio,

The moire effect is the dot-like grainy effect, right? So if I have to much resolution(dpi) it will make my cd cover look grainy? I was wondering about that because I asked the guy on tech support if it would make my image more graineir if I used a high dpi setting for a small size image and he said it wouldn't. He said it would just stack the dots and I wouldn't be able to tell.

Also, I cannot get a perfect scan of the cd cover I am scanning. The cd cover has a girl that I am using as the visiual point(which is a photo, not a drawing or painting). The color is great, but the image is not of the original. The problem is that the scanned image is quite a bit wider than the original image. The girl on the cd cover is skinny, but on the scanned image she looks short and wide. On the scaned image specs. the width is only like 20 pixels more than the heigth. But visiually it looks significantly different than the original. I tried to re-adjust the size to make the heigth more than width and it helps but then I get distortion. Shouldn't a $200.00 scanner scan the cd cover to it's actual size? Is it impossible to get a scan to look like the original and am I expecting to much?

Thanks,
-Darin

Just got a scanner...got a couple of questions

Reply #15 – 2003-06-22 00:23:05

Quote

Otherwise the thread will continue to attract discussions of resolution scaling, speckling, gaussian blur, masking, moire patterns, soap films, and other effects that, while interesting, are probably not related to the actual problem you had.

as you figured that is a public forum, so the solutions arent darlin-only, and yes the raster/moire stuff is quite interesting, i would say more than an occasionaly broken canon scanner, but thats just my view. B)

Just got a scanner...got a couple of questions

Reply #16 – 2003-06-22 02:24:58

Here's a small part of a CD booklet, scanned at 600 DPI, you can see the dots : Click

I simulated a moire effect on it : Click

But, trying to scan it at different resolutions (72, 150, 300, 350, 450, 500, 600, 700), I couldn't get any moire effect. It seems that scanners have improved since the 90's and can now scan without any moire effect (this is an Epson Perfection 1250).

But there are still dots. How to get rid of them ? Scanners have a "demoire" function included. I didn't find it explicited in the Epson Twain 5. I think it is defaulted in the "document" profile (above picture was scanned with the "photo" profile). This is the same thing, scanned with the document setting : Click
Not very interesting, eh ?

The advantage of the gaussian blur is to allow you set as much blur as you want : Click
This way, the dots are completely removed.

I don't know if there are some more effective filters in order to remove the dots. An FFT edit should be the ideal one : Click
If other people here have other software (I use Corel Photopaint 9), they can try to filter the picture in the first link above.

Now, in practice, if you want to print the sleeve, just leave the dots unchanged ! They won't be visible (while the blur filter will).
And if you want to display it on the screen, just scan it at an inferior resolution. At 150 DPI, the dots are barely visible : Click
This is a 72 DPI scan of the whole page, no need to remove dots, there are none : Click

A bit off topic, one could expect an FFT edit to be the only way to remove the real moire effect, as shown in the second link above, because the moire is bigger than the picture details. In practice it seems quite impossible. The fist problem is dealing with low frequencies. I've spotted the four points responsible for the moire effect with a pair of red arrows : Click. Can you see them ? I spent one minute the nose on the screen in order to find them !
Then here's the result : Click
The moire has been removed from where it was (the arm, the leg, the face...), but it has been added where is wasn't (the hair, the shoulder, the bag...) ! That was to be expected, because the four points removed from the FFT define a moire evenly covering all the picture, while the real moire doesn't.
I think this problem is similar to a lowpassed square wave. There is some "ripple" on the "lands", and we want a perfect square wave instead. The only way is to add the missing harmonics in order to complete the square wave. I don't see how I could do it in the FFT of the picture.

FFT process performed with AstraImage 2.0MAX : Click

Just got a scanner...got a couple of questions

Reply #17 – 2003-06-22 04:14:13

Is there a way where I can upload two jpeg files to show the comparesion of my scanner and a different scanner?

-Darin

Just got a scanner...got a couple of questions

Reply #18 – 2003-06-23 00:24:12

It should be possible if you go to the free webspace that your internet service provider should have offered with the internet connection you use.
Otherwise, if you're connecting from work, for example, you can send the pictures to me. Ask my mail by sending me a private message, in this case.

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