Removeing blue lines in scanned pencil drawings????

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Sat, 02 June 2007 13:00 Go to next message
Doane_Hoag (Photoshop begginer)
I have tried selective color and color replace, but have had poor results removing the "non reproducing" blue pencil lines from my pencil drawings that I scan into the computer in color.
I use blue lines to lightly block in the drawing before I draw with regular pencils, or during the drawing progress. The pencil lines have dark to very light lines and I don't want to loose the light lines in the process of removing the blue ones. Does anyone have some trick to share?
Thanks,
Doane
Sat, 02 June 2007 14:10 Go to previous messageGo to next message
Michael_D_Sullivan (Photoshop expert)
Maybe select the blue channel, then use a threshold adjustment?
Sat, 02 June 2007 14:40 Go to previous messageGo to next message
dave_milbut (Photoshop expert)
are you using black or colored pencils for the rest of your drawing? if regular black, scan in grayscale. that's the purpose of the blue pencil for markups. doesn't show up during b&w scanning.

if colored pencils, then mike's got a good suggestion.
Sat, 02 June 2007 20:50 Go to previous messageGo to next message
Lawrence_Hudetz (Photoshop expert)
Actually, not quite true, dave. If the blue line has a density greater than the paper density, it still will show up, unless the scan is done only on the blue channel, or in the old analog days, shot through a blue filter or with color blind emulsions.

The same is true with a yellow stain. With the filters available now in PS, match the stain color to a filter color and poof! There goes stain (in b&w only, of course)!

Mike's suggestion is right on.
Sat, 02 June 2007 21:25 Go to previous messageGo to next message
Michael_D_Sullivan (Photoshop expert)
The reason blue pencils are labeled as non-reproducing is that older copying machines and monochrome scanners typically used the blue spectrum for copying, so that blue showed up as white. Now, few copiers or scanners operate in this mode; they create an image using a sensor that is sensitive to multiple colors, whether the ultimate image is to be monochrome, grayscale, or color. This allows pictures and graphics to be reproduced in a somewhat recognizable fashion, and prevents yellow highlighting from coming out black, which is the case when a blue-oriented sensor or light source is used.

By using the blue channel, anything that was blue in the original image will be white or close to it. Black pencil lines, however, will remain black. Using the threshold allows you turn pixels that are above a certain point white. Alterrnatively, use the Levels adjustment on the blue channel to maintain better light/dark black pencil lines.
Sat, 02 June 2007 22:06 Go to previous messageGo to next message
dave_milbut (Photoshop expert)
older copying machines and monochrome scanners typically used the blue
spectrum for copying, so that blue showed up as white.




yup. that's what i was basing it on. sorry to be out of date.

ex-big-iron xerox copy jockey,
dave :)
Sat, 02 June 2007 22:38 Go to previous messageGo to next message
Phosphor (Photoshop expert)
DocuTechers of the World, UNITE!

:)
Sat, 02 June 2007 22:55 Go to previous messageGo to next message
dave_milbut (Photoshop expert)
9700 & 9900 here! :) scribble whatever you want in blue pencil, it wasn't gonna come out.
Sat, 02 June 2007 22:56 Go to previous messageGo to next message
Doane_Hoag (Photoshop begginer)
Thanks everyone.. sorry, let me try to be a bit more clear. I draw using 2b to 2h regular graphite pencils (not colored) on 100H architectural or onion skin tracing paper. I use blue "non reproducing" pencils for rough perspective layout lines, etc., in the preliminary sketching stages and as I am working in different areas as needed.
When I was working at a company a few years ago I used to take my pencil drawings over to a print shop and on their copy machines the blue lines would not show up in the copies, but at home now, I scan with an Epson Perfection (usually in two scans from 11x17), and quickly piece them togeather in the computer. During the scan I have no filter controls that I am aware of. I then do manipulations of the drawings in the computer, clean them up, etc. I also add more scanned in drawings, etc. to these as layers as needed. I finally print the manipulated drawings out on a HP Deskjet 1220c at 11x17 on HP brochure flyer paper.
Sat, 02 June 2007 23:10 Go to previous messageGo to next message
Lawrence_Hudetz (Photoshop expert)
Save them as RGB, Doane, then open the blue channel as a gray scale and correct the contrast. The blue should be gone. If not, send us a sample via Pixentral (http://www.pixentral.com/) and we can take a look.
Sat, 02 June 2007 23:48 Go to previous messageGo to next message
Doane_Hoag (Photoshop begginer)
Thanks, Lawrence, I do save them as RGB, but I'm not sure of your instructions. I'm not knowledgeable in all areas of PS..

If I go in channels and turn off everything except the blue channel, the blue lines pretty much dissapear in the image window, and if I then adjust the levels for the best retention of the light pencil lines while eliminating most of the blue lines, and then convert it to gray scale, that actually works better then anything I have tried before using the color selection tools. Is that what you were suggesting?
Thanks for your patience, if you want I can post one of the drawings on the link you gave as well.
Doane
Sun, 03 June 2007 01:36 Go to previous messageGo to next message
Lawrence_Hudetz (Photoshop expert)
Exactly, Doane.

Good Luck!
Sun, 03 June 2007 10:43 Go to previous messageGo to next message
Doane_Hoag (Photoshop begginer)
OK, I had looked in my CS help file and couldn't find anything about this.. I guess the days of hand drawn art work are disappearing.. ;~) anyway, thanks for all your help!
Sun, 03 June 2007 12:52 Go to previous messageGo to next message
John_R_Nielsen (Photoshop expert)
Right-click on the layer with your scanned drawing, and go to 'Blending Options'. Choose 'Blue' in the 'Blend if:' drop-down, and drag the white pointer at the right of "This Layer" to the left.

If you Alt-drag the pointer, it will split in two, with a smooth transition between the two.
Sun, 03 June 2007 16:07 Go to previous message
Doane_Hoag (Photoshop begginer)
Thanks, John, another good method to add to my notes.
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