how to remove diagonal lines

[Shibo2501]

Hi, I hope this wasn't discussed before but I searched the net a lot and couldn't find anyone with the same problem.
I bought an english translated manga and would like to read it on screen, so I scanned it.
It's color + 600 dpi.
I like the result except for these diagonal lines in all gray areas :View media item 21112A gaussian filter either won't work or will make the image too fuzzy and contour reinforcement won't help with that much fuzziness. I think gaussian filter was meant for descreening, not for this.
any help appreciated, thanks

 

[Mana Light]

As I thought, it was scanned form english ver. I suspect that english publisher didn't buy data of manga. Only buy copyright to publish (and buy data for color pages). Publisher scanned japanese tank then clean it and print again (not original files). This is why the quality is not good.
Anyways, sadly there is no pefect way to clean this raw. (Only level raws a bit to clean it then.)

 

[Gradonil_Ral]

Hello @Shibo2501
Did you use a standalone flatbed scanner or an "all-in-one" type of device? (I'm hoping it wasn't an office copier.)
Did you use some kind of scanning software provided with your scanner? If so, could you post a screenshot of the settings visible before scanning?

Are these lines visible on paper as well? Or just the scans? If they're on paper, then removing them will be quite difficult, if they're just on your scans, then you're using incorrect settings (or a wrong type of scanner).
One thing you could try is to scan in grayscale. There's really no reason to scan black and white pages in color anyway.

Publisher scanned japanese tank then clean it and print again

I don't believe that. I mean... there's no way there are publishers who'd do that... right?

 

[Mana Light]

Publishers in my country do it all the times. They do it to save money . It happens with other countries as well. You can buy japanese tank and translated ones to compare.
Just recently 1,2 young publishers buy data files (for Mahou tsukai no yome.)
Anyways it is the only way to explain about quality of that raws. (other reason is quality of paper)

 

[Shibo2501]

Why thanks everyone
No the lines are not visible on paper. However, the pages are only 18x13 cm. In grayscale, the result is awful. I won't insult you with it.
I'm not used to scan at all so my settings or hardware are possibly wrong.
I scan with plustek smartoffice PS 286 plus.
My software is Paperscan (I also tried Irfanview and Gimp, same result).
Maybe I should change to Gimp anyway because paperscan can't modify levels.
Anyway here are the settings I used so far (screenshots would be in french, so...) :
Format : 8.5 x 14 Pouces
Mode : color (24 bits)
600 ppp
Light : zero, contrast : zero, gamma : 1
color matching, color suppression, moiré suppression, filter : none,
shadow : zero, highlight : 255,
of course this is twain.

--- Double Post Merged, Nov 10, 2016, Original Post Date: Nov 10, 2016 ---

Who said "try grascale" ? you're a genius.
My first try in 400 ppp was a disaster, and now in 600, here it goes :

View media item 21113
I'm so glad. Since I'm here, any suggestions to make it even better appreciated, but I'm happy anyway.

--- Double Post Merged, Nov 10, 2016 ---

for some reason, one out of every 4 pages still looks like this :View media item 21114

 

[Gradonil_Ral]

Oh, you have a document scanner. It's made for speed, not quality. You'd need a flatbed scanner to achieve HQ scans.

I'm not sure why the 4th page still has those lines, but I think you should try scanning with the producer software instead of different apps.
Here's a video that showcases some of the scanning options:
Try adjusting some options if you still have trouble. You might also try saving in TIFF. (Huge, uncompressed files, but no loss in quality.)

 

[Mana Light]

http://puu.sh/sdDvD/6d024645c8.png
I think the cause is your scanner so try scan with another scanner.
Like Gradonil_Ral said, you need flatbed scanner. Btw I use LIDE 120 that is cheap.

What made different is not grayscale. It is 600 dpi that made different. (btw i scan with color because the back paper i used it is not black). Color or grayscale doesn't matter. jpg is fine. png is acutally more than enough. tiff is no need.
Anyways, you should try other scanners.

I still defend my opinion that publisher didn't use original files because dots are bad. (not round)

 

[Gradonil_Ral]

It is 600 dpi that made different

Well, he said in his original post that he scanned in color at 600dpi. So there was no dpi change.

I still defend my opinion that publisher didn't use original files because dots are bad. (not round)

IMO that's due to the document scanner. The page is in motion during the scanning process. There's no way the dots would be as round as they should.

 

[Mana Light]

it is 400 dpi :v

Let wait to see raws with other scanner.

 

[Gradonil_Ral]

So it is. He clearly messed up there :P

 

[Shibo2501]

Hi, thanks again. Of course, I'm bad at this, it's all new to me.
I guess I have to buy a flatbed if I want perfect results. I don't know if the problem is the autoloader being not totally smooth when loading, or the fact that there is another page printed in the back instead of a black background.
In the meantime, other tests with disabling the both sides scan yield much better results. Now I get faint lines only or none. I'm not unhappy with the result. Plus using the autoloader has the advantage of speed and it automatically crops borders perfectly. It's useful if you're in a rush and want to scan 300 pages in a row.
Btw I ordered a french edition and the quality is just awful. The translation is terrible too. I'll stick to english. Well at least they tried and published it.

 

[Gradonil_Ral]

Yea, scanning with flatbed results in better quality, but it takes a lot of time. Scanning a volume takes about 90mins (if not more). And that's when you're scanning two pages at a time and at 300dpi. (I can scan at 300dpi at 150% scale to get very, very close results to 600dpi in a lot less time than scanning at 600dpi would take.)