Weird printing issues question!

[awfulquiet]

Hey everyone, so I'm working on a new small comic and I've done a couple of test prints. And I've run into a strange issues.

I penciled in blue line, inked over it, scanned in with color drop to remove the blue lines. Works great. Looks perfect on my screen.

But when I print, I'm getting blue line showing through, specifically my ruled lines for lettering.

Here's a screenshot from the PDF no lines:

Here's a pic of the printed page from that PDF, lines!:

Anyone have any ideas? I'm exporting from Clip Studio to PDF, printing from PDF. Printing on my Brother laser printer.

[michaelkennedy]

I get the same issue often with clip studio even after a bunch of adjustment filters and hand erasing some time bits of pencil escape my screen noticing. The hight the DPI scan the worse the issue.

[awfulquiet]

I did a lot of experimenting and had to set the color expression on everything to grey or monochrome ans that got rid of the phantom lines, but messed with some of my tones so I went back ans re-did all of my digital edits and clean ups with everything set to monochrome from the start.

I did notice if I zoomed waaaaay in on the file in Clip i could see some stray blue pixels that didn't get dropped during scanning. But nothing that I would expect to show up so clearly in print. It was maddening.

[BubblesZine]

Sometimes the preview on photoshop can reduce actual detail. Like when you have a filter applied, but when you merge the filter, the desired look changes. I've found it comes from being zoomed out too much (even if it doesn't feel like you are) and not seeing what's really happening on a hi-res image. It's finicky...

[justareed]

You've still got some color in those whites!!  My guess is that the printer, when quantizing stuff or whatever printers do, is lifting the color that is there from like .1% up to 5% where you can see it, because that's the lowest it can print - and stuff gets lifted to there instead of dropped as white.

I pulled your screenshot into photoshop and put a curves on it to stretch the values hiding in your white area and make them more visible.  You can see they're still there!



I color picked from the affected region to confirm that it's not straight white which would be #FFFFFF or 0, 0, 0, 0 in CMYK.  You can see a value of 1 there in the C and Y channels of the sampled pixel - just enough to throw off the printer I guess!  I makes sense that it worked for you in monochrome because those value were probably effectively rounded down, or because there's a 0 for the K there.  (I actually don't know CMYK/printing very well at all - just guessing!!)


If I were you I would do a curves/levels like this to preserve most of your grays as is, but punch out the artifacts in the whites.  Just scooting the upper threshold down a couple values is enough to take out those lines.  I don't have CSP yet, but I'm sure they gotta have curves or levels in there...

[awfulquiet]

Dec 3, 2022 5:43:37 GMT justareed said:

You've still got some color in those whites!!  My guess is that the printer, when quantizing stuff or whatever printers do, is lifting the color that is there from like .1% up to 5% where you can see it, because that's the lowest it can print - and stuff gets lifted to there instead of dropped as white.

I pulled your screenshot into photoshop and put a curves on it to stretch the values hiding in your white area and make them more visible.  You can see they're still there!

View Attachment

I color picked from the affected region to confirm that it's not straight white which would be #FFFFFF or 0, 0, 0, 0 in CMYK.  You can see a value of 1 there in the C and Y channels of the sampled pixel - just enough to throw off the printer I guess!  I makes sense that it worked for you in monochrome because those value were probably effectively rounded down, or because there's a 0 for the K there.  (I actually don't know CMYK/printing very well at all - just guessing!!)
View Attachment

If I were you I would do a curves/levels like this to preserve most of your grays as is, but punch out the artifacts in the whites.  Just scooting the upper threshold down a couple values is enough to take out those lines.  I don't have CSP yet, but I'm sure they gotta have curves or levels in there...
View Attachment

Thanks so much for doing the investigative legwork! Definitely gonna try some things differently next time.

[jporcellino]

(For black and white artwork) I also use non-photo blue to pencil without having to erase. I then scan into PS via Greyscale and run the grey file through the threshold command to get to straight black and white. That usually takes care of any lingering remnants of pencil that made it through the scan.