Underdrawing that disappears — how non-photo blue works
The traditional manga production workflow: sketch the composition and panel layout in non-photo blue pencil, ink over the sketch with dip pen and production black ink, scan the page with the scanner set to exclude the blue wavelengths, and the pencil marks are gone from the output — no erasing required. Non-photo blue works because standard photographic scanners (both CCD and CIS sensor types) can be set to exclude specific colour wavelengths when producing a greyscale output. The light blue of non-photo blue pencils falls in the wavelength range that is excluded in greyscale mode, meaning the marks are simply not recorded by the sensor when the setting is applied. The result is a clean scan of the inked linework without any pencil residue, no erasing marks on the inking surface, and no risk of erasing disrupting the ink lines. The technique requires testing on your specific scanner before committing to a project — scanner behaviour varies between models and software.
Col-Erase versus Pilot Color Eno — which to choose
The Col-Erase Non-Photo Blue is a traditional wooden pencil — erasable (which is useful for correcting the underdrawing before inking), with a 7.4mm barrel diameter that most illustrators find comfortable for extended sketching. It needs sharpening, which maintains a consistent point size and sharpness but requires a sharpener. The Pilot Color Eno 0.7mm is a mechanical pencil — no sharpening needed, consistent 0.7mm line width throughout, and more portable. The mechanical pencil is preferred by illustrators who want consistency in the underdrawing line width; the wooden pencil is preferred by those who want the flexibility of a sharper point for detail and a broader point for rough blocking.
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FREQUENTLY ASKED QUSTIONS (FAQ)
Will non-photo blue actually disappear on my scanner?
On most flatbed scanners set to greyscale with blue wavelengths excluded — yes. The specific setting varies by scanner model and software: look for 'remove non-photo blue', 'drop cyan channel', 'greyscale with blue exclusion', or test whether the standard greyscale mode on your scanner excludes the blue wavelengths automatically. Test on a scrap page with your specific non-photo blue product and scanner before beginning a project. Some older or lower-specification scanners may not have adequate blue exclusion capability.
Does it work on standard office photocopiers?
Less reliably than scanners. Many office photocopiers do reproduce pale blue marks, particularly at higher contrast settings. Test your specific photocopier before relying on non-photo blue for photocopy production. For zine production that relies on photocopying rather than scanning, erasing the underdrawing before photocopying is the safer approach.
Col-Erase or Pilot Color Eno — which should I start with?
If you currently use wooden pencils for sketching and want a direct like-for-like substitution in non-photo blue, Col-Erase. If you currently use mechanical pencils or want consistent line width without sharpening, Pilot Color Eno. Both produce non-photo blue marks that behave identically on scanners. The choice is a matter of preferred pencil format.